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Fall 2020

December 16th: Wil Kao

Stanford University
Topological pumping of a 1D dipolar gas into strongly correlated prethermal states

Abstract: Highly excited eigenstates of interacting quantum systems are generically “thermal,” in the sense that physical observables behave as they would in thermal equilibrium–all initial conditions give rise to locally thermal behavior at times past the intrinsic dynamical timescale. Systems in which thermalization is absent are of great fundamental interest because they violate equilibrium statistical mechanics, and of technological interest because some quantum information encoded in these states evades decoherence. For the purpose of tackling this line of inquiry, ultracold neutral atoms in dilute gas offers a suitable tabletop platform that is well isolated from the environment and readily scalable to the thermodynamic limit.

In this talk, I will describe our recent efforts of creating nonthermal states in a bosonic quantum gas of dysprosium, the most magnetic element, confined in quasi-1D waveguides. With repulsive long-range dipolar interactions that are two orders of magnitude stronger than alkali atoms, a highly excited super-Tonks-Girardeau gas is stabilized against collapse and thermalization. Stiffness and energy-per-particle measurements indicate that the system is dynamically stable regardless of short-range contact interaction strength. This metastability enables the cycling of contact interactions from weakly to strongly repulsive, then strongly attractive, and finally weakly attractive via two neighboring magnetically tuned collisional resonances. Iterating this quantum holonomy cycle allows an energy-space topological pumping method to create a hierarchy of increasingly excited prethermal states. In addition to being the first experimental realization of a dipolar Luttinger liquid, the result opens up an unexplored regime of quantum control and may have wide-ranging implications for understanding the onset of chaos in near-integrable systems.

Bio: Wil Kao is an Applied Physics Ph.D. candidate at Stanford University, where he works on quantum simulation using dipolar quantum gases under the supervision of Prof. Benjamin Lev. He holds a B.A.Sc. in Engineering Science from the University of Toronto.

11am
Via Zoom (
https://mit.zoom.us/j/96436775519)

December 9th: Dr. Artur Hermans

U. Gent
Micro-transfer-printing of thin-film devices on silicon nitride photonic integrated circuits: on-chip lasers, modulators, and detectors

Abstract: Silicon nitride photonic integrated circuit (PIC) technology has come forth as one of the main photonic integration platforms. Silicon nitride PIC technology has many great features such as low waveguide loss, a wide transparency range (400 nm – 4000 nm), and the possibility of low-cost mass manufacturing using CMOS infrastructure. Yet, many applications require on-chip lasers, modulators, and detectors, which are not available in standard silicon nitride PIC technology. This talk will show how a technique called micro-transfer-printing can be used to integrate thin-film devices, made out of various materials, with silicon nitride PICs to realize on-chip lasers, modulators, and detectors. Micro-transfer-printing can be done in a massively parallel fashion on a wafer-scale, thereby offering a path to high-volume, low-cost production.

Bio: Artur did his BSc degree in Engineering (Electronics and information technology) from the Vrije Universiteit Brussel in 2012. Afterwards, he entered the European MSc in Photonics program during which he spent a semester at Ghent University, the Vrije Universiteit Brussel, the University of St Andrews and the Swiss Federal Institute of Technology in Lausanne (EPFL). At EPFL, he did his master’s thesis with Professor T. J. Kippenberg. In 2014, he joined the Photonics Research group to work on low-temperature processed thin films of second-order nonlinear optical materials for silicon nitride photonic integrated circuits, under supervision of Professor R. Baets and Professor S. Clemmen. For this work he was awarded a PhD degree in 2019. Currently, he is working as a postdoc in the Photonics Research Group on III-V-on-SiN mode-locked lasers.

11am
Via Zoom (https://mit.zoom.us/j/97962565434)

December 2nd: Professor Laura Waller

UC Berkeley
End-to-end learning for computational microscopy

Abstract: Computational imaging involves the joint design of imaging system hardware and software, optimizing across the entire pipeline from acquisition to reconstruction. Computers can replace bulky and expensive optics by solving computational inverse problems. This talk will describe end-to-end learning for development of new microscopes that use computational imaging to enable 3D fluorescence and phase measurement. Traditional model-based image reconstruction algorithms are based on large-scale nonlinear non-convex optimization; we combine these with unrolled neural networks to learn both the image reconstruction algorithm and the optimized data capture strategy.

Bio: Laura Waller is the Ted Van Duzer Associate Professor of Electrical Engineering and Computer Sciences (EECS) at UC Berkeley, a Senior Fellow at the Berkeley Institute of Data Science, and affiliated with the UCB/UCSF Bioengineering Graduate Group. She received B.S., M.Eng. and Ph.D. degrees from the Massachusetts Institute of Technology (MIT) in 2004, 2005 and 2010, and was a Postdoctoral Researcher and Lecturer of Physics at Princeton University from 2010-2012. She is a Packard Fellow for Science & Engineering, Moore Foundation Data-driven Investigator, Bakar Fellow, OSA Fellow and Chan-Zuckerberg Biohub Investigator. She has recieved the Carol D. Soc Distinguished Graduate Mentoring Award, Agilent Early Career Profeessor Award (Finalist), NSF CAREER Award and the SPIE Early Career Achievement Award.

11am
Via Zoom (https://mit.zoom.us/j/93157422522)

November 25th: Peter O’Brien

Tyndall National Institute
Photonic Packaging & Systems Integration – from Research to Pilot Line Manufacturing

Abstract: This talk will give an overview of Tyndall’s capabilities in developing advanced photonic and electronic sub-systems and how these are integrated to produce fully functioning prototypes. The talk will also present Tyndall’s capabilities to enable scale-up from prototypes to pilot scale manufacturing and the drive to develop packaging standards. The talk will also discuss new research activities to develop a more scalable packaging technology for mass markets, taking lessons from the electronics industry to build a new global standard in photonic packaging.

Bio: Prof. Peter O’Brien is head of the Photonics Packaging & Systems Integration Group at the Tyndall Institute, University College Cork in Ireland. He is also Director of the PIXAPP European Packaging Pilot Line (www.pixapp.eu), Director of the new European Photonics Innovation Academy and Deputy Director of the Science Foundation Ireland Photonics Centre, IPIC. He previously founded and sold a photonics start-up company and was a researcher in millimeter wave devices at Caltech and NASA’s Jet Propulsion Laboratory.

11am
Via Zoom (https://mit.zoom.us/j/94970479716)

November 4th: Professor Xiadong Xu

University of Washington
Phonons and Excitonic Complex in a Monolayer Semiconductor

Abstract: The coupling between spin, charge, and lattice degrees of freedom plays an important role in a wide range of fundamental phenomena. Monolayer semiconductor is an emerging platform for studying these coupling effects due to unique spin-valley locking physics for hosting rich excitonic species and reduced screening for strong Coulomb interaction. In this talk, I will present the observation of both symmetry-allowed and -forbidden valley phonons, i.e. phonons with momentum vectors pointing to the corners of Brillouin zone, in a monolayer semiconductor WSe2. From the analysis of Landé g-factors and emission polarization of photoluminescence peaks, we identified the efficient intervalley scattering of quasi particles in both exciton formation and light emission process. These understandings enable us to unravel a series of photoluminescence peaks as valley phonon replicas of neutral and charged dark excitons, as well as deeply bound excitonic states with anomalously long population lifetime (>5 µs). Our work not only shows monolayer WSe2 is a prime candidate for studying interactions between spin, pseudospin, and zone-edge phonons, but also opens opportunities to engineer collective quantum optical phenomena using homogenous intrinsic defect-bound excitons in ultraclean two-dimensional materials.

Bio: Xiaodong Xu is a Boeing Distinguished Professor in the Department of Physics and the Department of Materials Science and Engineering at the University of Washington. He received his PhD (Physics, 2008) from the University of Michigan and then performed postdoctoral research (2009-2010) at the Center for Nanoscale Systems at Cornell University. His nanoscale quantum optoelectronics group at University of Washington focuses on creation, control, and understanding of novel device physics based on two-dimensional quantum materials.

12pm
Via Zoom (https://mit.zoom.us/j/94397730742)

October 14th: Professor Wim Bogaerts

Ghent University
Variability-aware circuit design techniques for silicon photonic circuits

Abstract: Silicon Photonics is probably the only technology that really enables large-scale integration of photonic building blocks. This is made possible by the high-end manufacturing technology developed for the CMOS industry, combined with the very high refractive index contrast of silicon and silicon dioxide. This allows submicron waveguides that can be packed close together on a chip. However, the high index contrast makes the silicon waveguides also extremely sensitive to fabrication variations. When combining many elements in a circuit, this variability will affect the overall circuit yield, limiting the effective scale of the circuits. Therefore, circuit design for silicon photonics needs to incorporate the effects of fabrication variations early in the design process, optimizing the circuit layout to maximize the yield. We will discuss these effects and the workflows needed to implement variability aware design for silicon photonics.

Bio: Wim Bogaerts is a professor in the Photonics Research Group at Ghent University and IMEC. He completed his PhD in 2004, pioneering the use of CMOS tools to make photonic circuits. Between 2000 and 2010, he was instrumental in the buildup of IMEC’s silicon photonics technology. In parallel, he also started developing the design tool IPKISS to implement complex silicon photonic circuits. In 2014, he co-founded Luceda Photonics, bringing his design tools to the market. In 2016 he returned full-time to Ghent University and IMEC on research grant of the European Research Council. His research now focuses on the challenges for large-scale photonic circuits and the new field of programmable photonics. He is a senior member of IEEE, OSA and SPIE.

11am
Via Zoom (https://mit.zoom.us/j/95629349135)

Summer 2020

September 23rd: Professor Christophe Galland

EPFL
Toward molecular cavity optomechanics: light-vibration entanglement and atomic fluctuations in plasmonic nanocavities

Abstract: Molecular systems offer many degrees of freedom potentially useful for quantum technologies, at frequencies ranging from few MH to hundreds of THz. Among them, vibrational modes can be addressed in their quantum ground state even at room-temperature. Inspired by recent developments in cavity optomechanics, we leverage the inelastic scattering of light by molecular vibrations (vibrational Raman scattering) to generate entangled states between photons and phonons in a crystal at ambient conditions, and to demonstrate non-classical statistics of the vibrational excitations.

With the aim of pushing this technique to the level of single molecules, we also develop plasmonic nanocavities with embedded Raman active molecules, which are expected to provide giant optomechanical rates approaching 1 THz. In contrast with naïve models used to simulate the optical response of nanocavities based on bulk material properties, we discover pronounced fluctuations in carrier dynamics inside the plasmonic metal, which are amplified by the large Purcell factor and reflected in “plasmonic blinking”, i.e. jumps in intensity and energy of the intrinsic luminescence from the metal.

Overall, our results evidence that molecular oscillators are promising for ultrafast quantum information processing, but that pushing molecular quantum technologies from ensemble measurements to the nanoscale will require a much deeper understanding of metal-molecule interactions and atomic-scale dynamics in plasmonic nanostructures.

11am
Via Zoom (
https://mit.zoom.us/j/95705420294)

September 16th: Bevin Huang

University of Washington
Emergent phenomena in two-dimensional magnetic crystals

Abstract: The recent discovery of 2D van der Waals (vdW) magnets brings new and exciting opportunities to explore 2D magnetism by harnessing the unique features of atomically thin materials, such as electrostatic gating for magnetoelectronics and flexible heterostructure engineering for emergent interfacial phenomena. In this talk, I will focus on the magneto-optical discoveries enabled by one of these vdW magnets, the magnetic insulator chromium triiodide (CrI3). I will begin by introducing the layered antiferromagnetic properties of CrI3 and its tunability using electric fields. Then, I will discuss the host of magneto-optical phenomena that arise from symmetry-breaking in this 2D magnetic insulator: electrical generation of Kerr signal in an antiferromagnet; giant polarization rotation and magnetoelectrical switching of phonon Raman activity; and discrete angular momentum conservation and its imprint on 2D magnon optical selection rules. At the end, I will provide brief highlights of the progress over the field of magnetic vdW materials and survey the vdW heterostructures that have been realized using these 2D vdW magnets.

11am
Via Zoom (https://mit.zoom.us/j/93890264418)

September 9th: Professor Jero Maze

Institute of Physics, Pontificia Universidad Católica de Chile, Santiago, Chile
Symmetry and phonon considerations of single emitters for quantum applications

Abstract: An active search for new emitters in large bandgap materials has taken place over the last years with the purpose of enabling novel quantum applications. Despite many defects have been found, few of them own the required properties for quantum applications where coherence is the most desired property. In this talk, we will discuss how the inner structure of these systems and the interaction with their immediate environment allow or avoid their use for quantum applications. In particular, we will show how the symmetry of these defects determine their properties and their coupling to the environment, specially phonons, and the consequences of such coupling for enabling applications in quantum information and metrology. As an example, we will focus on the emission spectrum of silicon-vacancy centres in diamond and recently discovered single emitters in hexagonal Boron-Nitride and propose possible defect configurations for them. In addition, we will consider the effect of phonons on the relaxation of spin 1/2 electronic systems subject to Jahn-Teller distortion leading to electronic spin resonance suppression, an expected effect although never estimated. Finally, we will discuss the effect of non-radiative transitions of the nitrogen-vacancy centre in diamond on the polarisation of its electronic spin and nearby nuclear spins. Open questions will be highlighted.

Bio: Jero R. Maze is an Associate professor and Director of Research and Postgraduate Studies at the Institute of Physics of Pontificia Universidad Católica de Chile. He is an industrial electrical engineer and earned his PhD in Physics from Harvard University in 2010. Professor Maze researches at the interface between condensed matter and quantum optics. His research includes the study of nano systems where individual degrees of freedom such as the electric or spin charge can be accessed with high level of control to create novel applications in metrology and information storage. His investigation involves both experimental exploration and theoretical studies of nano systems such as trapped molecules in solids and their interaction with the environment with the goal of creating novel sensors for material science and biology, and generating single-molecule based optoelectronics devices.

11am
Via Zoom (https://mit.zoom.us/j/98230458500)

September 2nd: Dr. Jonas Nils Becker

Imperial College London
Broadband optical quantum memories: From atomic vapors to solid-state systems

Abstract: Photonic encoding of quantum information is key to the realization of scalable quantum technologies such as provably-secure quantum communication over long distances or interconnected local nodes of a distributed quantum processor. However, many of the tasks involved in these applications, such as single-photon-generation, photon-photon gates, and entanglement generation, rely on probabilistic processes, posing barriers to efficiency and scalability. Optical quantum memories, devices that can store and recall quantum states of light on demand, can overcome these limitations by synchronizing probabilistic processes as well as providing additional functionalities such as coherent filtering, temporal mode manipulation, and memory-enhanced photon-photon interactions.

In this seminar, I will discuss quantum memory protocols based on off-resonant two-photon interactions in lambda- and ladder-type atomic systems, originally developed in our group for alkaline vapor-based memories, and I will highlight recent results focusing on noise suppression and temporal mode selection and conversion using this platform. In the second part of this talk I will then show how these protocols can be adapted to solid-state systems and present recent work utilizing silicon vacancy centers in diamond as well as Pr3+:Y2SiO5, paving the way for scalable and potentially chip-integrable solid-state quantum memories with high bandwidths.

Bio: Dr. Jonas N. Becker is a Research Associate in quantum information in Professor Ian Walmsley’s Ultrafast Quantum Optics Group at Imperial College London. Dr. Becker received his PhD in physics from Saarland University, Germany, working with Professor Christoph Becher on spectroscopic investigations and quantum control of silicon vacancy defects in diamond, and was also a visiting student in Professor Mete Atatüre’s group at the University of Cambridge, UK. After his PhD, he joined Professor Walmsley’s group at the University of Oxford to combine his expertise with the team’s knowledge of atomic vapor-based quantum memories, working toward quantum memories in the solid state. The group recently moved to Imperial College London, UK, where he is now leading the Quantum Memories and Solid-State subteams. Dr. Becker’s current research interests include solid-state quantum memories, novel defects in diamond for qubit and memory applications, as well as quantum thermodynamic investigations utilizing defects in diamond.

11am
Via Zoom (https://mit.zoom.us/j/96070947566)

July 1st: Professor Liang Jiang

University of Chicago
Quantum Error Correction for Sensing and Simulation

Abstract: Quantum error correction is a powerful method for protecting a quantum system from the damaging effects of noise. Besides computation and communication, quantum error correction can also improve the performance of quantum sensing and quantum simulation. We study how measurement precision can be enhanced through quantum error correction by identifying a necessary and sufficient condition for achieving the Heisenberg limit using quantum probes subject to Markovian noise. We develop a new class of bosonic encoding that can preserve the bosonic nature at the logical level while correcting excitation loss error, which will enable error-corrected quantum simulation. The talk will provide a perspective on using quantum error correction for various applications.

Bio: Liang Jiang theoretically investigates quantum systems and explores various quantum applications, such as quantum sensing, quantum transduction, quantum communication, and quantum computation. His research focuses on using quantum control and error correction to protect quantum information from decoherence to realize robust quantum information processing. He has worked on modular quantum computation, global-scale quantum networks, room-temperature nano-magnetometer, sub-wavelength imaging, micro-optical quantum transduction, and error-correction-assisted quantum sensing and simulation.

Prof. Jiang received his BS from Caltech in 2004 and PhD from Harvard University in 2009. He then worked as a Sherman Fairchild postdoctoral fellow at Caltech. In 2012, Jiang joined the faculty of Yale University as an assistant professor and later as an associate professor of Applied Physics. He was awarded the Alfred P. Sloan Research Fellowship, and the David and Lucile Packard Foundation Fellowship in 2013. In 2019, Jiang moved to his current position as professor at the University of Chicago Pritzker School of Molecular Engineering.

11am
Via Zoom (https://mit.zoom.us/j/92699431172)

 

Spring 2020

June 3rd: Professor Andrea Blanco-Redondo

NOKIA Bell Labs
Novel solitons and topological quantum states using silicon photonics

Abstract: In this talk I will review our work on nonlinear and topological photonics in silicon. In the first part of my talk, I will unveil our latest results on the recently discovered pure-quartic solitons, including our demonstration of the first pure-quartic soliton laser and its new energy-width scaling law. In the second part, I will cover recent developments in the field of topological quantum photonics with special emphasis on our experimental demonstration of topologically protected path-entangled states in silicon waveguide arrays.

11am
Via Zoom (
https://mit.zoom.us/j/97314540377)

 

April 8th: Professor Volker J Sorger

George Washington University
Photonic Intelligent Information Processing

Abstract: Photonic technologies are at the forefront of the ongoing 4th industrial revolution of digitalization supporting applications such as 5G networks, virtual reality, autonomous vehicles, and electronic warfare. With Moore’s law and Dennard scaling now being limited by fundamental physics, the trend in processor heterogeneity suggests the possibility for special-purpose photonic processors such as neural networks or RF-signal & image filtering. Here unique opportunities exist, for example, given by algorithmic parallelism of analog computing enabling non-iterative O(1) processors, thus opening prospects for distributed non-van Neumann architectures.

In the first part of the talk I will highlight strategies and experimental validations of emerging nanophotonic opto-electronic devices. These include heterogeneous integration of emerging materials into Silicon photonic integrated circuit to exploit new functionality and device-scaling laws such as efficient modulators, detectors, and photonic nonvolatile memory.

In the second half, I will share our latest work on analog photonic processors to include a) a photonic tensor core processor paradigm, b) a feed-forward fully-connected neural network using electro-optic nonlinearity, c) mirror symmetry perception via coincidence detection of spiking neural networks, d) a Fourier-optics based convolutional processor for real-time processing, e) mesh-based reconfigurable photonic & metatronic PDE solvers, and f) a photonic parallel binary-weighted DAC.

In summary, photonics connects the worlds of electronics and optics, thus enabling new classes of efficient optoelectronics and analog processors by employing the distinctive properties of light.

Bio:
Volker J. Sorger is an Associate Professor in the Department of Electrical and Computer Engineering, and the leader of the Integrated Nanophotonics lab at the George Washington University. He received his PhD from the University of California Berkeley and MS from UT Austin. His research focuses on integrated photonics and analog information processing such as programmable photonic circuits and neuromorphic computing. His work was recognized by Presidential Early Career Award for Scientists and Engineers (PECASE), the Emil Wolf prize from the Optical Society of America, the AFOSR Young Investigator (YIP) award, the Hegarty Innovation prize, the National Academy of Sciences paper-of-the-year award, and both the Early Career and Outstanding Research awards at GWU. He is the editor-in-chief of the Nanophotonics and the OSA division chair for Optoelectronics-and-Photonics. He serves at the boards of OSA and SPIE, and is a senior member of IEEE, OSA & SPIE. Further details at sorger.seas.gwu.edu.

11am
Via Zoom (https://mit.zoom.us/j/445437334)

 

Winter 2020

January 15th: Dr. Michael Strain

University of Strathclyde, Glasgow, UK
Integrated Photonics: Micro-LED systems and Hybrid Material PICs

Abstract: In this presentation I will cover two main themes of research from our group. In the first, high speed micro-LED devices will be discussed. Individual GaN LED devices, with dimensions below 100 m, exhibit modulation bandwidths in the 100’s of MHz range, allowing for Gb/s data communications links. Direct bonding of micro-LED chips, in pixelated array format, to CMOS drivers can be used to realise small form factor optical projectors with high-speed refresh rates and low size, weight and power requirements. Recent applications of these arrays include high speed, long range data links, 3D imaging and time of flight ranging.
The second part of the presentation will detail a transfer printing technique used for the heterogeneous integration of photonic integrated circuit components from multiple material platforms. Single-mode waveguide devices can be fabricated using standard lithography and etch processes and then subsequently transferred to host PICs in a secondary material, with absolute positional accuracy in the 100 nm range. Hybrid III-V and diamond devices on silicon and GaN waveguide platforms will be presented.

Bio:
Michael Strain was awarded the MEng (Electrical and Mechanical Engineering), MASc (Photonics) and PhD (Photonics) from the Universities of Strathclyde, Toronto and Glasgow respectively. After a period as a post-doctoral research in the James Watt Nanofabrication centre at the University of Glasgow, he moved to the Institute of Photonics at the University of Strathclyde. He is now deputy director of the Institute and senior lecturer in photonic semiconductor devices. Michael’s group has research interests covering the design and micro-fabrication of integrated optical devices in a range of materials, including III-Nitrides and diamond. The development of a high accuracy transfer printing technique for the heterogeneous integration multiple materials on a single chip is a key component of their work. The group is also developing micro-LED pixel arrays for data communications, imaging and high speed projection applications.

11am
Haus Room, 36-428

 

Fall 2019

December 4th: Stefan Abel

IBM Research, Zurich
A Strong Pockels Effect in Optical Devices on Silicon

Abstract: An important building block in integrated optical circuits is an efficient link between the optical and electrical domain. Well-known examples of such links are integrated high-speed modulators to convert electrical signals into optical signals at very high-speed, and low-power tuning elements to compensate for variations in the device operation temperature and for device-to-device variations during fabrication. To enable such electro-optic links, the two most widely used physical effects are the plasma-dispersion effect and Joule heating. Although these effects are attractive to use due to their compatibility with standard photonic fabrication processes, their performance in integrated devices is intrinsically limited by high insertion losses and high-power dissipation.

Over the past decade, we established an alternative electro-optic switching technology by embedding a Pockels material into silicon-based photonic devices. We reached this goal by developing a process to fabricate ferroelectric barium-titanate (BTO) thin films on silicon substrates using advanced epitaxial deposition techniques and by developing a BTO process technology. By realizing integrated hybrid BTO/silicon devices, we demonstrated record-high, in-device Pockels coefficients of >900 pm/V [1]. The Pockels effect in BTO-based photonic devices indeed enables extremely fast data modulation at rates beyond >40 Gbps and ultra-low-power electro-optic tuning of silicon and silicon-nitride waveguides. We also show ways of how to integrate and use BTO in plasmonic slot waveguide structures for very compact optical devices. With the development of a wafer-level integration scheme of single-crystalline BTO layers to a 200 mm process, we could demonstrate a viable path to combine the BTO-technology with existing fabrication routes [2].

With major breakthroughs in the past years, BTO has emerged as a strong candidate for a novel generation of electro-optic devices. Major achievements of the BTO technology will be covered in the presentation, ranging from important materials aspects, device development, integration concepts, and novel applications in the area of quantum computing, high-speed communication, and neuromorphic optical computing.

References:
1. S. Abel et al., Nat. Mater. 18, 42?47 (2019).
2. F. Eltes et al., J. Light. Technol. 37, 1456?1462 (2019).

Bio:
Dr. Stefan Abel is a Research Staff Member at IBM Research – Zurich. He joined IBM in 2009 after finishing his studies of nanoscale engineering at the University of Würzburg (Germany) and received his Ph.D. in engineering from the University of Grenoble, France. His research focuses on novel photonic devices that exploit the unique properties of complex oxides, such as ferroelectricity and optical nonlinearities, and on neuromorphic architectures and devices, such as memristors and reservoir computing. He leads the development of BTO technologies at IBM. Stefan is author or co-author of more than 100 research contributions ? including 25 patents, invited talks, and publications as book chapter and in high-impact journals.

11am
Haus Room, 36-428

 

October 18th: Jacob B. Khurgin

Johns Hopkins University
Some myths and realities in nanophotonics

Abstract: (1) Excited carriers in metals: from icy cold to comfortably warm to scalding hot

The field of plasmonics in recent years has experienced a certain shift in priorities. Faced with undisputable fact that loss in metal structures cannot be avoided, or even mitigated (at least not in the optical and near IR range) the community has its attention to the applications where the loss may not be an obstacle, and, in fact, can be put into productive use. Such applications include photo-detection, photo-catalysis, and others where the energy of plasmons is expended on generation of hot carriers in the metal. Hot carriers are characterized by short lifetimes, hence it is important to understand thoroughly their generation, transport, and relaxation in order to ascertain viability of the many proposed schemes involving them.
In this talk we shall investigate the genesis of hot carriers in metals by investigating rigorously and within the same quantum framework all four principle mechanisms responsible for their generation: interband transitions, phonon-and-defect assisted intraband processes, carrier-carrier scattering assisted transitions and Landau damping. For all of these mechanisms we evaluate generation rates as well as the energy (effective temperature) and momenta (directions of propagation) of the generated hot electrons and holes. We show that as the energy of the incoming photons increases towards the visible range the electron-electron scattering assisted absorption becomes important with dire consequences for the prospective “hot electron” devices as four carriers generated in the process of the absorption of a single photon can at best be characterized as “lukewarm” or “tepid” as their kinetic energies may be too small to overcome the potential barrier at the metal boundary. Similarly, as the photon energy shifts further towards blue the interband absorption becomes the dominant mechanism and the holes generated in the d-shell of the metal can at best be characterized as “frigid” due to their low velocity. It is the Landau damping process occurring in the metal particles that are smaller than 10nm that is the most favorable on for production of truly “hot” carriers that are actually directed towards the metal interface.
We also investigate the relaxation processes causing rapid cooling of carriers. Based on our analysis we make predictions about performance characteristics of various proposed plasmonic devices.

(2) Non-magnetic optical isolators: what works and what does not?

Optical Isolator is a key component of photonic circuits and systems. An optical isolator requires non-reciprocal propagation i.e. breaking time inversion symmetry. Time symmetry cannot be broken in a linear optical system without magnetic field and/or gain and loss, hence all the practical isolators at this point are based on Faraday (magneto optic) effect which makes it difficult to develop isolators for planar integrated photonic circuits. Therefore, in recent years a strong effort has been mounted to develop non-magnetic isolators. A number of schemes had been proposed and demonstrated, such as devices with temporal modulation, acousto-optic and opto-mechanical isolators, various nonlinear schemes and parity time schemes with gain and loss.

In this talk we review performance characteristics of all these schemes and find them lacking any advantages in comparison to magnetic isolators. Most of the proposed schemes are severely limited in bandwidth and require high power consumption. Moreover, often they are not true optical isolators but are “optical diodes” in the sense that they do not offer full isolation.
We then make a case for the optical isolator based on second and third order nonlinearities that have good isolation and high dynamic range and offer detailed analysis of this exciting family of devices.

10am
Grier A, 34-401A

 

October 16th: Daniel J. Blumenthal

Terabit Optical Ethernet (TOEC) Center, University of California at Santa Barbara
Quiet Light and Integrated Ultra-Narrow Linewidth SBS Lasers

Abstract: Optical sources with near perfect linewidths and frequency stability approaching that of an atomic transition have ushered in the era of “quiet light.” These spectrally pure, ultra-stable sources serve as the heart of large-scale precision high-end scientific experiments used in time-keeping, positioning, quantum and spectroscopy, yet have been relegated to the table-top. In this talk the basics of quiet light, the limiting sources of noise and drift, and how such light is measured and characterized will be briefly discussed. The generation and stabilization of quite light using a new class of chip-scale integrated Stimulated Brillouin Scattering (SBS) laser capable of sub-Hz fundamental linewidth emission and frequency reference cavities will be described. Reduction of the integral linewidth and laser stabilization close-to-carrier noise using miniature stabilization cavities will be described as will improving the long term frequency drift and fractional frequency stability to unprecedented levels for photonic integrated lasers. Applications of quiet light and these sources will be described including atomic cooling, ultra-low noise microwave generation and ARPA-e funded FRESCO project energy efficient high capacity coherent communications project

Bio: Daniel J. Blumenthal received the Ph.D. degree from the University of Colorado, Boulder (1993), the M.S.E.E. from Columbia University (1988) and the B.S.E.E from the University of Rochester (1981). He is a Professor in the Department of ECE at UCSB, Director of the Terabit Optical Ethernet Center (TOEC) and heads the Optical Communications and Photonics Integration (OCPI) group (ocpi.ece.ucsb.edu). Dr. Blumenthal is Co-Founder of Packet Photonics Inc. and Calient Networks and 23 patents. He has published over 460 papers in the areas of optical communications, ultra-narrow linewidth integrated lasers, optical gyros, InP and ultra-low loss silicon nitride waveguide photonic integration, nano-photonic devices and microwave photonics. He is co-author of Tunable Laser Diodes and Related Optical Sources (New York: IEEE–Wiley, 2005) and has published in the Proceedings of the IEEE.

Dr. Blumenthal is a Fellow of the National Academy of Inventors (NAI) and a Fellow of the IEEE and Optical Society of America. He has served on the Board of Directors for National LambdaRail (NLR) and as an elected member of the Internet2 Architecture Advisory Council. He is recipient of a Presidential Early Career Award for Scientists and Engineers (PECASE), a National Science Foundation Young Investigator Award (NYI) and an Office of Naval Research Young Investigator Program (YIP) Award and has served on numerous program committees including OFC, Photonics in Switching and as guest editor of multiple IEEE Journal special issues.

11am
Haus Room, 36-428

 

October 9th: Rajesh Menon

University of Utah
Combining Nanofabrication & Computation enables ultra-thin, multi-functional optics & photonics

Abstract: Micro- and nanostructures have recently been widely applied to enhance the performance of optical components and systems. Structures whose characteristic dimensions are greater than the wavelength of interest, l, can effectively manipulate the scalar properties of light, while nanostructures with dimensions << l/2 can manipulate the vector properties of light. Computational techniques, such as nonlinear optimization, coupled with electromagnetics modeling can drive the designs of novel optical and photonic components and systems. When guided by manufacturing constraints, such techniques can result in highly practical, low-cost, ultra-compact (on the order of l x l) and multi-functional integrated-photonics components, such as polarization beam-splitters, wavelength splitters, couplers,, waveguide bends, etc. We’ll also describe a nanophotonic cloak that enables two devices to be placed closer together than is otherwise feasible, leading to an increase in integration density. Applying these techniques at the microscale (> l regime) has resulted in flat super-achromatic lenses, planar spectrum-splitting solar concentrators, and ultra-high efficiency displays.

We can recognize the functions enabled by optics and photonics as a form of information manipulation, enabling highly non-intuitive forms of optical systems such as photography with no lenses or microscopy with only a surgical needle or multi-spectral imaging with a diffractive element.

Bio: Rajesh Menon combines his expertise in nanofabrication, computation and optical engineering to impact myriad fields including super-resolution lithography, metamaterials, broadband diffractive optics, integrated photonics, photovoltaics and computational optics. His research has spawned over 100 publications, 40 patents, and 4 spin-off companies. Rajesh is a Fellow of the Optical Society of America, and Senior Member of the SPIE and the IEEE. Among his other honors are a NASA Early Stage Innovations Award, NSF CAREER Award and the International Commission for Optics (ICO) Prize. He currently directs the Laboratory for Optical Nanotechnologies (http://lons.utah.edu/) at the University of Utah. He received S.M. and Ph.D. degrees from MIT.

11am
Haus Room, 36-428

 

September 11th: Thomas Alexander

IBM TJ Watson Research Center
Qiskit: A Framework for All of Your NISQ Needs

Abstract: Programming quantum computers in the Noisy Intermediate-Scale Quantum (NISQ) regime is a developing science. Device hardware is noisy, constrained and rapidly evolving. At IBM Q we are working towards achieving quantum advantage in the near term and error-correction in the long term. Qiskit is IBM Q’s open-source software development kit (SDK) for leveraging today’s quantum processors with the aim of enabling the quantum processors of tomorrow. Through software based techniques we can navigate and mitigate some of the limitations of current quantum computing systems, and enable research into new techniques for future hardware. To this aim we present OpenPulse an open and extensible framework for controlling quantum systems at the level of microwave pulses. We hope to enable further research into new control, characterization and scheduling techniques that will enable the construction of a next-generation of quantum computing systems.

Bio: Thomas Alexander is a developer at IBM Q working on Qiskit at TJ Watson Research Center. At IBM, Thomas focuses on the interface between the quantum circuit description of a quantum computation and the microwave pulses that will implement these logical operations in hardware. Thomas is the lead developer of the pulse module within Qiskit and spends much of his time thinking about how we can develop a computing infrastructure that will enable the construction and control of large-scale quantum computers.

11am
Haus Room, 36-428

Summer 2019

August 15th: Euan J. Allen

University of Bristol, UK
Integrated Continuous-Variable Quantum Optics and Homodyne Detection

Abstract: In the last few years there have been a number of efforts looking into developing the continuous-variable quantum optics toolkit for integrated photonics. These have covered several platforms including silicon nitride [1,2], lithium niobite [3,4], and silicon [5]. In this talk I will discuss the motivation and challenges associated with such experiments and will introduce work in Bristol to engineer fast homodyne detectors in silicon. Using electronic – photonic chip-to-chip bonding we demonstrate shot-noise limited detectors with a 1.7 GHz 3 dB bandwidth and non-zero clearance up at 8 GHz. These represent the fastest homodyne detectors suitable for quantum applications to date. I will also discuss efforts to create a source of squeezed vacuum in silicon and the associated challenges with using this platform for continuous-variable state generation.

[1] Vaidya, V. D., et al. “Broadband quadrature-squeezed vacuum and nonclassical photon number correlations from a nanophotonic device.” arXiv preprint arXiv:1904.07833 (2019).
[2] Cernansky, Robert, and Alberto Politi. “Nanophotonic source of broadband quadrature squeezing.” arXiv preprint arXiv:1904.07283 (2019).
[3] Lenzini, Francesco, et al. “Integrated photonic platform for quantum information with continuous variables.” Science advances 4.12 (2018): eaat9331.
[4] Takanashi, Naoto, et al. “Detection of 3-dB continuous-wave squeezing at 1.55 {\mu} m from a fiber-coupled single-pass PPLN ridge waveguide.” arXiv preprint arXiv:1906.09749 (2019).
[5] Raffaelli, Francesco, et al. “A homodyne detector integrated onto a photonic chip for measuring quantum states and generating random numbers.” Quantum Science and Technology 3.2 (2018): 025003.

Bio:

Euan received his PhD from the Quantum Engineering Centre for Doctoral Training and the Quantum Engineering Technology Labs at the University of Bristol. During this time, he worked with Dr. Jonathan Matthews on optical quantum sensors, continuous-variable quantum optics, and the interface of these two disciplines. Euan has continued to work in Bristol on integrated continuous-variable quantum optics and has recently been awarded an EPSRC Doctoral Prize Fellowship to work on large-scale integrated homodyne networks.

11am
Haus Room, 36-428

 

July 24th: Laura Kim

California Institute of Technology
Graphene Plasmons for Mid-Infrared Nanophotonics and Ultrafast Phenomena

Abstract: Graphene supports surface plasmons bound to an atomically thin layer of carbon, characterized by tunable propagation and distinctly strong spatial confinement of the electromagnetic energy. Such collective excitations in graphene enable the strong interactions of massless Dirac fermions with light. In this talk, I will discuss fundamental properties of graphene plasmons both near and far from equilibrium in the scope of achieving active sub-wavelength control of light-matter interactions and generating mid-infrared radiation. I will present theoretical predictions and experimental validations of non-equilibrium graphene plasmon excitations via ultrafast optical pumping, originating from a previously unobserved and experimentally overlooked decay pathway: hot plasmons generated from optically excited carriers. Connecting experiment to theory offers a positive outlook for gain and coherent amplification of plasmons in graphene. This work reveals novel infrared light emitting processes, both spontaneous and stimulated, and provides a platform for achieving ultrafast, ultrabright mid-infrared light sources.

Bio:
Laura received her B.S. in chemical engineering (2013) and Ph.D. in materials science (2019) from California Institute of Technology as a National Science Foundation Graduate Fellow under the supervision of Professor Harry Atwater. Her doctoral research focused on understanding light-matter interactions in two-dimensional materials ranging from mid-infrared nanophotonics to ultrafast phenomena in graphene.

11am
Grier A, 34-401A

 

July 3rd: Dr. Alex Lukin

Harvard University
Probing entanglement and correlations in a many-body-localized system

Abstract: An interacting quantum system that is subject to disorder may cease to thermalize due to localization of its constituents, thereby marking the breakdown of thermodynamics. The key to our understanding of this phenomenon lies in the system’s entanglement, which is experimentally challenging to measure. We realize such a many-body-localized system in a disordered Bose-Hubbard chain and characterize its entanglement properties through particle fluctuations and correlations. We observe that the particles become localized, suppressing transport and preventing the thermalization of subsystems. Notably, we measure the development of non-local correlations, whose evolution is consistent with a logarithmic growth of entanglement entropy – the hallmark of many-body localization. Our work experimentally establishes many-body localization as a qualitatively distinct phenomenon from localization in non-interacting, disordered systems. We also fallow the transition between thermal and many-body localized state and unveil a characteristic correlation structure in the critical region.

Bio: Dr. Lukin revised this Ph.D. from Harvard University where he worked under the supervision of professor Markus Greiner. He used a quantum gas microscope to study quantum many-body systems out of equilibrium, in particular, the role of entanglement in the system’s dynamics.

11am
Haus Room, 36-428

Spring 2019

Jan 30: Dr. Jelmer Renema

University of Twente, the Netherlands
The Hardness of Boson Sampling with Imperfections

Abstract: The next milestone in experimental quantum information processing is the demonstration of a quantum advantage, i.e. the unambiguous demonstration of an information processing task, no matter how trivial, at which a quantum device outperforms a classical computer. This is possible using photonics, where it involves sending single photons through a random unitary network and drawing samples from the output in the photon number basis. This is known as boson sampling.

A major practical hurdle on the way to constructing a boson sampler is that it is poorly understood how imperfections in the system, such as photon loss and finite distinguishability (wave function overlap) degrade the hardness of simulating the quantum interference occurring in such a device.

In this talk, I will address this problem by demonstrating a classical algorithm which uses these two imperfections to perform an efficient classical simulation of a boson sampler. In the limit of large numbers of photons, this algorithm is efficient in the number of photons for any nonzero level of imperfections, which shows that the equivalent of an error threshold for boson sampling does not exist.

Furthermore, by considering a fixed number of photons, we can demarcate those areas of the parameter space where a quantum advantage demonstration using photonics is ruled out. This algorithm can therefore be used to guide the design of future photonic quantum advantage demonstrations. I will show that strong qualitative improvements to photonics technology are needed to demonstrate a quantum advantage using photonics.

Bio: Dr. Jelmer Renema is currently a Veni Fellow with Pepijn Pinkse at the University of Twente, working on multiphoton quantum optics and the quantum optics of scattering media. He is also the CTO of QuiX B.V., a photonic quantum technologies company. Previously, he was a Junior Research Fellow at the University of Oxford, with Ian Walmsley, working on integrated quantum optics. Before that, he obtained his PhD on the detection mechanism of nanowire superconducting single photon detectors in the group of Dirk Bouwmeester and Martin van Exter in Leiden.

11am
Haus Room, 36-428

 

Feb 6: Adrian Menssen

University of Oxford
Interfering Distinguishable Photons: Understanding Three and Four Photon Interference

Abstract: Quantum interference of two independent photons in pure quantum states is fully described by the particles’ distinguishability: the closer the particles are to being identical, the higher the degree of quantum interference. When more than two particles are involved, the situation becomes more complex and interference capability extends beyond pairwise distinguishability. We study many-particle interference in three and four photons in a series of experiments. We show that for three photons the three distinct distinguishabilities between pairs of photons are not sufficient to fully describe the photons’ behaviour in a scattering process, but that additionally a fourth parameter, a collective phase, governs the scattering process. Furthermore, we experimentally demonstrate that surprisingly four photons can interfere even when they are pair-wise orthogonal. We illustrate these effects in a graph theoretical picture we developed.

11am
Haus Room, 36-428

 

April 11: Kaoru Minoshima

University of Electro-Communications (Tokyo, Japan)
Intelligent Optical Synthesizers:Versatile control of optical waves enables studies from molecular physics to astronomy

4pm
2019 Hermann Anton Haus Lecture
Haus Room, 36-428

Reception at 5pm
Fourth Floor, Building 32

 

May 2nd: Stefan Krastanov

Yale Quantum Institute
Stochastic Calibration of Quantum Hardware and Optimization of Circuits

Abstract: The precise control and evaluation of quantum hardware requires a well calibrated model of the dynamical laws governing it. Methods like state and process tomography permit such calibration in principle, but they require a very large number of measurements and dealing with the noise inherent to the hardware makes them fragile. Instead of these methods, we will see how tools borrowed from compressed sensing and machine learning provide for cheaper, more robust, and higher fidelity calibration procedure.

Going one step higher the technology stack, we need to use these calibration techniques to actually prepare non-classical resources for use in quantum computation. One of the most ubiquitous such resource is quantum entanglement. We will see how one can optimize the entanglement distillation circuits for the error model of the actual hardware. The optimized circuits perform substantially better than a general distillation circuit by virtue of being optimized for the particularities of the hardware — this way the results from the previously discussed calibration procedure inform the design of upper layers of the technology stack.

2pm
CUA Seminar Room, 26-214

 

May 13th: Sivan Trajtenberg-Mills

Tel Aviv University
Nonlinear Holograms for All-Optical Shaping of Light Beams

Abstract: In this talk, I will discuss the control of light by engineered nonlinear photonic crystals. By modulating the quadratic nonlinearity of the crystal using computer generated holography, one can control the spatial shape and the trajectory of the generated light. Furthermore, I will present how a two-level system analogy can help design crystals where the geometric phase accumulated can be all optically controlled. I will continue in showing how these methods might be useful for generating and controlling light at a quantum level. To facilitate the design of nonlinear crystals for quantum optics applications, I will describe a simulator that we developed, for predicting the spatial distribution of spontaneously generated bi-photons. Also, I will discuss how we can use quasi-crystal designs in order to generate multi-photon states.

Short bio: Sivan Trajtenberg-Mills is a Physics Ph.D. student in Tel Aviv University (Israel), under the supervision of prof. Ady Arie. She recieved The Eric and Wendy Schmidt Postdoctoral Award for Women in Mathematical and Computing Sciences, won the Weinstein Institute Signal Processing award, and the minisitry of science Shulamit Aloni scholarship for Ph.D studies. She was the president of the OSA Tel Aviv University student chapter, and has been active in promoting women in Physics by co-founding ShePhyiscs, the first women students in physics club in TAU.

3pm
Haus Room, 36-428

 

Fall 2018

September 12: Dr. Andrew R. Lupini

Oakridge National Laboratory
Imaging and Controlling Single Atoms with an Electron Beam

Abstract: Since the invention of the electron microscope the imaging resolution has traditionally been limited by the aberrations of the electron lenses. Fifty years after the first proposal outlining how to correct these imperfections, modern aberration-correctors have become widespread across many laboratories. Computer control with rapid feedback to measure and correct the controls forms an important part of these systems, and advanced methods to interpret and process the rich information stream from these instruments present numerous exciting challenges.
Over the last few years, electron microscopy has started to undergo a transition from merely being used as an imaging device to a tool capable of addressing and in some cases even control single atoms. In his famous talk, There’s Plenty of Room at the Bottom, Richard Feynman highlighted both the benefits of improving the resolution of the electron microscope and the potential applications of writing or controlling single atoms. Recent work has begun to demonstrate the feasibility of manipulating single atoms in 2D materials, however given the ubiquitous use of silicon in modern electronics, there remains a need to achieve this feat inside 3D crystals technologically relevant materials. In this talk I will show some of the progress towards these goals and demonstrate using the electron beam to control dopant atoms one-by-one inside a semiconductor crystal.

Dr. Lupini obtained his Ph.D. in Physics from the Cavendish Laboratory of Cambridge University in the UK, under the supervision of Dr. Andrew Bleloch, in 2001. Dr. Lupini is one of the inventors of the first aberration-corrector in a scanning transmission electron microscope to demonstrate an improved resolution. He is currently a R&D staff member in the Materials Science and Technology Division of Oak Ridge National Laboratory in Tennessee. His research interests include all forms of electron microscopy and spectroscopy, especially as applied to new or quantum materials.

11am
Haus Room, 36-428

 

September 26: Jean-Philippe MacLean

University of Waterloo
Direct characterization of ultrafast energy-time entangled photon pairs

Abstract: In the famous example suggested by Einstein, Podolsky and Rosen (EPR), two particles can be highly correlated in position and momentum. For photons, strong EPR-like correlations can also occur in the energy-time degree of freedom, that is, between the frequency and the time of arrival of the photons. This type of entanglement enables fundamentally quantum effects such as dispersion cancellation and clock synchronization. However, detection of this entanglement and observation of these effects can require ultrafast time resolution beyond the capabilities of current photon detectors. Thus, for operations on ultrafast timescales, more powerful and complex methods are required.

We use a nonlinear technique known as optical gating to surpass the limitations in current detectors and achieve subpicosecond time resolution for single photon pairs. Optical gating in conjunction with single photon spectrometers then enables us to measure both the spectral and temporal correlations of a two-photon state, allowing us to observe for the first time EPR correlation but in frequency and in time.

Jean-Philippe is originally from Montreal. He completed his undergraduate in Physics at McGill University in 2013. During his undergraduate, he worked on high-intensity ultrafast optics at the INRS in Varennes and then moved to quantum optics for PhD at the University of Waterloo.

11am
Haus Room, 36-428

 

October 10: Ken Segall

Colgate University
Think Super: Artificial Neurons made from Superconductors

Abstract: Our research focuses on the design, fabrication and testing of integrated circuits which can simulate neuron spiking dynamics on very fast timescales in a biologically realistic way [1]. These circuits are based on a low-temperature, superconducting electronics technology (Josephson junctions) that has already been successful in creating ultra-sensitive magnetometers, superconducting qubits, high-performance radiation detectors, high-speed digital processors, and the primary voltage standard in the U.S. The short spiking times in these artificial neurons combined with analog scaling properties give this approach a potentially unprecedented ability to investigate long term dynamics of large networks [1]. In addition, these artificial neurons dissipate almost no power, making them a candidate for a low-power, neuromorphic computing technology.

We have performed the first experiments on two superconducting neurons which are mutually coupled with artificial axons and synapses [2,3]. In some regions of parameter space the neurons are desynchronized. In others, the Josephson neurons synchronize in one of two states, in-phase or anti-phase. An experimental alteration of the delay and strength of the connecting synapses can toggle the system back and forth in a phase-flip bifurcation, which is a biologically-realistic phenomenon [4] Firing synchronization states are calculated >70,000 times faster than conventional digital approaches. With their speed and low energy dissipation (10-17 Joules/spike), this set of proof-of-concept experiments establishes Josephson junction neurons as a viable approach for improvements in neuronal computation as well as applications in neuromorphic computing.

1 P. Crotty, D. Schult, and K. Segall, Phys Rev E. 82 (2010).
2 K. Segall, S. Guo, P. Crotty, D. Schult, and M. Miller, Physica B 455, 71 (2014).
3 K. Segall, M. LeGro, S. Kaplan, O. Svitelskiy, S. Khadka, P. Crotty, and D. Schult, Phys Rev E. 95 (2017).
4 N. M. Dotson and C. M. Gray, Phys Rev E. 94 (2016).

 

October 24: Thomas Ohki

Raytheon BBN Technologies
Enabling Technology for Beyond Intermediate Scale Quantum Computing Systems

Abstract: The goal of implementing of a cryptologically meaningful quantum computing system requires not only advances in physical qubit performance and fault tolerant operation but almost an equally hard problem of engineering an achievable system. This requires the ability to grow to large numbers of qubits while incorporating new scalable technologies as the total system size and complexity also grows. For quantum computing systems, significant advances and demonstrations can be made at small to moderate scales enabled by “brute force” methodologies. One of my focuses has been to understand what gaps may exist in the near future for these systems and to start advancing these immature enabling technologies. Whether this is novel cryogenic microwave components, control and readout electronics or novel materials, each advance has its own relevance in the timeline of a large scale system. Balancing the demand vs readiness for a capability can be a complicated dance between physicist and engineers, government mission roadmaps and commercial market expectations. We show progress toward some of these enabling technologies areas for quantum information systems.

Bio: Lead of the Quantum Engineering and Computing group at Raytheon BBN Technologies which is focused on development and applications of superconducting devices for quantum information, microwave systems and beyond CMOS digital technologies. Active research areas include superconducting quantum and classical computing, as well as superconducting devices hybridized with spintronic and 2-D materials. He has built a world class quantum computing research laboratory in Cambridge Massachusetts and superconducting device fabrication capabilities at Raytheon.

 

October 31: Mahdi Naghiloo

Washington University, St. Louis
Optimal precision in frequency estimation using a quantum bit

Abstract: In quantum metrology, one seeks to take advantage of quantum properties to maximally utilize the available measurement resources. For parallel resources, such as the number of quantum systems, entanglement can be utilized to achieve Heisenberg scaling. Similarly, one can also utilize quantum coherences to optimally exploit the serial resource, time. We demonstrate how quantum coherence can be optimally harnessed through coherent control to expedite a frequency estimation task. In our experiment, an unknown external oscillating signal causes the quantum system to undergo periodic changes. By applying quantum pulses on top of the oscillating signal, the state of the system could be controlled so that the final readout of the quantum system became highly sensitive to the precise value of the oscillation frequency. The underlying physical source of the advantage is related to the fact that the energy of the quantum system is time-dependent, which causes the quantum states corresponding to different frequencies to accelerate away from each other, giving enhanced distinguishability in a given time. This result demonstrates a fundamental quantum advantage for frequency estimation.

 

December 12: Vinod Menon

City University of New York (CUNY)
Control of Light-matter Interaction in 2D Materials

Abstract: Two-dimensional (2D) Van der Waals materials have emerged as a very attractive class of optoelectronic material due to the unprecedented strength in its interaction with light. In this talk I will discuss approaches to enhance and control this interaction by integrating these 2D materials with microcavities, and metamaterials. I will first discuss the formation of strongly coupled half-light half-matter quasiparticles (microcavity polaritons) [1] and their spin-optic control [2] in the 2D transition metal dichacogenide (TMD) systems. Prospects of realizing condensation and few photon nonlinear switches using Rydberg states in TMDs will also be discussed. Following this, I will discuss the routing of valley excitons in 2D TMDs using chiral metasurfaces [3]. Finally, I will talk about room temperature single photon emission from hexagonal boron nitride [4] and the prospects of developing deterministic quantum emitters using them [5].

References:

[1] X. Liu, et al., Nature Photonics 9, 30 (2015)

[2] Z. Sun et al., Nature Photonics 11, 491 (2017)

[3] S. Guddala et al., ArXiv 1811.00071

[4] Z. Shotan, et al., ACS Photonics 3, 2490 (2016)

[5] N. Proscia, et al. Optica 5, 1128 (2018).

Bio: Vinod Menon is a Professor of Physics at the City College and Graduate Center of the City University of New York (CUNY). He is also an IEEE Distinguished Lecturer in Photonics (2018-19). He joined CUNY in fall 2004 as part of the initiative in photonics. Prior to joining CUNY he was at Princeton University (2001-2004) where he was the Lucent Bell Labs Post-Doctoral Fellow in Photonics. He received his MSc in Physics (Quantum Optics specialization) from the University of Hyderabad, India in 1995 and his Ph.D. in Physics from the University of Massachusetts in 2001. His current research interests include cavity QED with two-dimensional semiconductors, controlling transport and energetics in organic molecules through strong light-matter coupling, and engineered nonlinear optical materials. More details about his group can be found at www.lanmp.org

 

Fall 2017

October 4: Haitan Xu

Yale University
Topological and nonreciprocal dynamics in an optomechanical system

Non-Hermitian systems exhibit rich physical phenomena that open the door to qualitatively new forms of control. In this talk, I will introduce our recent work on topological and nonreciprocal dynamics in a non-Hermitian optomechanical system. Specifically, we realized topological energy transfer between nearly degenerate modes by adiabatically encircling an exceptional point (a singularity of the complex spectrum). We also demonstrated that this energy transfer is non-reciprocal: a given topological operation can only transfer energy in one direction. We have extended the topological and nonreciprocal dynamics to highly non-degenerate modes by exploiting a generic form of nonlinearity, which should allow these effects to be exploited in a very wide range of physical systems.

11am
Haus Room, 36-428

 

Charles Tahan * Special seminar on Monday this week!

Laboratory for Physical Sciences, University of Maryland
Enabling silicon quantum computers with always-on, exchange-only (AEON) qubits

After almost two-decades of sustained effort in making spin-based qubits, silicon still has great promise as the technology of choice for future quantum computers. After a brief update on the field, I will discuss our recent work proposing new qubit and coupling approaches for silicon quantum dots that attempt to overcome the biggest challenges facing construction of a silicon quantum computer. I will end by discussing what semiconductor and superconducting qubit designers can learn from each other and other promising new research directions.

4pm
Grier A, 34-401A

 

October 18: Kevin Fischer

Stanford University
Scattering of Coherent Pulses from Quantum-Optical Systems

Quantum optics is the study of a finite dimensional quantum system coupled to one or more baths with infinite degrees of freedom. For most of the field’s history, the infinite dimensionality of the problem led quantum physicists to believe that general solutions for the entire evolution operator were intractable. However, a quiet revolution is occurring in our understanding of the way finite dimensional systems interact with a bath. By recasting the system-bath interaction into a temporal mode basis, it becomes clear that the system interacts with each temporal mode only briefly before visiting the next. This machinery enables us to write down a simple enumeration of the system-bath dynamics [1], and we use this result to show how short laser pulses driving a quantum two level system preferentially result in the formation of two-photon bound states [2]. Our technique is generally applicable to a wide range of problems from stimulated emission at the single-photon level to understanding pulsed emission from spontaneous parametric downconversion sources.

[1] KA Fischer, et al., Scattering of Coherent Pulses from Quantum-Optical Systems, arXiv:1710.02875.
[2] KA Fischer, L Hanschke, et al., Signatures of two-photon pulses from a quantum two-level system, Nature Physics 13, 649–654 (2017).

11am
Haus Room, 36-428

 

October 25: Alex Sushkov

Boston University
Probing microscopic dynamics of a two-dimensional disordered dipolar spin system

We investigate the microscopic dynamics of disordered many-body dipolar spin systems using nitrogen-vacancy (NV) centers in diamond. Naturally-occurring electronic spins on the surface of a diamond crystal form a two-dimensional dipolar spin system, which is probed and manipulated via a shallow NV center, a few nanometers below the surface. We observe slow decay of the spin autocorrelation functions under a variety of experimental conditions.

11am
Haus Room, 36-428

 

November 1: Andrei Faraon

Caltech
Flat and conformal optics with dielectric metasurfaces

Flat optical devices based on lithographically patterned sub-wavelength dielectric nano-structures provide precise control over optical wavefronts, and thus promise to revolutionize the field of free-space optics. I discuss our work on high contrast transmitarrays and reflectarrays composed of silicon nano-posts located on top of low index substrates like silica glass or transparent polymers. Complete control of both phase and polarization is achieved at the level of single nano-post, which enables shaping of the optical wavefront with sub-wavelength spatial resolution. Using this nano-post platform, we demonstrate lenses, waveplates, polarizers, arbitrary beam splitters and holograms. Devices that provide multiple functionalities, like simultaneous polarization beam splitting and focusing are implemented. By embedding the metasurfaces in flexible substrates, conformal optical devices that decouple the geometrical shape and optical function are shown. Multiple flat optical elements are integrated in optical systems such as planar retro-reflectors and Fourier lens systems with applications in ultra-compact imaging systems. Applications in various types of microscopy are discussed.

11am
Haus Room, 36-428

 

November 8: Matthew Shaw

NASA Jet Propulsion Laboratory
Superconducting Nanowire Single Photon Detectors for Deep-Space Optical Communication and Quantum Optics

Abstract: Superconducting nanowire single photon detectors (SNSPDs) are the highest performance detectors available for time-correlated single photon counting in the infrared and ultraviolet. We discuss work at JPL to develop 64-pixel SNSPD arrays for the ground terminal of NASA’s Deep Space Optical Communication project, the first experimental demonstration of optical communication from deep space. We will also discuss ultraviolet SNSPDs integrated with ion traps for quantum computing, high-temperature SNSPDs based on MgB2, and ultra-high-time resolution SNSPDs.

Bio: Matt Shaw is leading the development of superconducting nanowire single photon detectors at the Jet Propulsion Laboratory in Pasadena, California. He has been a member of the superconducting devices and materials group at JPL since 2011. Prior to that, he was a postdoc in Applied Physics at Caltech. He was born and raised in Fairbanks, Alaska.

11am
Haus Room, 36-428

 

November 15: K. C. Fong

Raytheon BBN Technologies
Graphene thermal physics for optics and quantum electronics

Compared to its electrical counterpart, the peculiar thermal properties of the pseudo-relativistic electrons in graphene are less explored. Interestingly, the combination of low heat capacity and strong thermal isolation from phonons make the graphene electrons a promising material for some unique optics and quantum electronics applications. I will present some ideas and results of high-sensitivity graphene detectors for the superconducting quantum information processing, future NASA mission on cosmic infrared background, and optical interconnects. This work is performed in an interdisciplinary collaboration between Englund’s group at MIT, Hone’s group at Columbia University, Kim’s group at Harvard, and Raytheon BBN Technologies.

Ref: Phys. Rev. Applied 8, 024022 (2017)

11am
Haus Room, 36-428

 

November 29: Peter McMahon

Stanford University
Non-von Neumann computing using networks of optical parametric oscillators

Abstract: Combinatorial optimization problems are central in numerous important application areas, including operations and scheduling, drug discovery, finance, circuit design, sensing, and manufacturing. There is a long history of attempts to find alternatives to current von Neumann-computer-based methods for solving such problems, including neural networks, DNA computing, and most recently adiabatic quantum computation and quantum annealing.

Networks of coupled optical parametric oscillators (OPOs) are an alternative physical system, with an unconventional operating mechanism, for solving the Ising problem, which is an NP-hard optimization problem. We have realized a fully-programmable 100-spin Ising machine using a network of OPOs, and with it can solve many different Ising problem instances. Our design supports all-to-all connectivity among the implemented spins via a combination of time-division multiplexing and measurement feedback.

In this talk I will describe our work on constructing Ising machines using OPO networks with feedback, and will present the experimental results from our first prototype system.

[1] P.L. McMahon, et al. Science 354, 6312, pp. 614-617 (2016).

Bio: Peter received his Ph.D. in Electrical Engineering in 2014 from Stanford University in the group of Yoshihisa Yamamoto. His graduate work was on the development of building blocks for quantum computers and quantum repeaters using semiconductor systems. He subsequently began a postdoctoral appointment jointly in the groups of Hideo Mabuchi and Yoshihisa Yamamoto, working on the development of hybrid optical-electronic computing machines using principles and techniques borrowed from quantum optics.

11am
Haus Room, 36-428

 

December 6: Oliver Benson

Humboldt-Universitaet zu Berlin
Hybrid Quantum Technology Based on Quantum Emitters in Condensed Phase

A quantum hybrid system can be defined as consisting of two dissimilar physical systems that share a joint quantum state. Aside from being a fundamentally interesting object, several applications such as quantum information processing (quantum computers, quantum repeaters) or quantum sensing have been suggested. Bringing two dissimilar systems in a joint quantum state can be established by entangling them with photons or surface plasmon polaritons (SPPs) followed by joint measurements. Here we provide an overview of different approaches in these directions pursued in our labs. We introduce different kinds of quantum emitters (quantum dots, defect centers in diamond, molecules) as stationary quantum systems. Photon sources as part of a quantum hybrid architecture [1,2] can provide the ‘glue’ for such dissimilar quantum systems. We report on our recent results on non-linear photon conversion to the telecom band [3], photon collection from single emitters [4], and quantum logic elements using SPPs [5]. Future directions towards a higher level of integration will be discussed.

[1] “Assembly of hybrid photonic architectures from nanophotonic constituents“, O. Benson, Nature 480, 193-199 (2011).
[2] “Bright source of indistinguishable photons based on cavity-enhanced parametric down-conversion utilizing the cluster effect”, A. Ahlrichs, O. Benson, APL 108, 021111 (2016).
[3] “Heralded wave packet manipulation and storage of a frequency-converted pair photon at telecom wavelength”, T. Kroh, A. Ahlrichs, B. Sprenger and O. Benson, Quant. Sci. Techn. 2, 034007 (2017).
[4] “Wiring up pre-characterized single-photon emitters by laser lithography“, Q. Shi, B. Sontheimer, N. Nikolay, A.W. Schell, J. Fischer, A. Naber, O. Benson, M. Wegener, Sci. Rep. 6, 31135, (2016).
[5] “Design and numerical optimization of an easy-to-fabricate photon-to-plasmon coupler for quantum plasmonics“, G. Kewes, A.W. Schell, R. Henze, R.S. Schönfeld, S. Burger, K. Busch, and O. Benson, Appl. Phys. Lett. 102, 051104 (2013).

11am
Haus Room, 36-428

 

Spring 2018

February 7: Charles Black

Director, Center for Functional Nanomaterials Brookhaven National Laboratory
Nanoscience at the Center for Functional Nanomaterials, a National Scientific User Facility

The Center for Functional Nanomaterials (CFN) is a national scientific user facility operated at Brookhaven National Laboratory for the U.S. Department of Energy. One of five DOE Nanoscale Science Research Centers, the CFN offers external Users a supported research experience with top-caliber scientists and access to state-of-the-art instrumentation at no cost via a peer- reviewed proposal process. The CFN mission is advancing nanoscience to impact society, by being an essential resource for the nanoscience community and producing breakthroughs in nanomaterials research.

After an overview of the scientific facilities, research directions, and the process of becoming a CFN user, I will describe CFN research using block copolymer self-assembly for design of nanostructured materials. Block copolymer thin films provide a robust method for generating regular, uniform patterns at length scales in the range of ten nanometers, over arbitrarily large areas. A significant advantage of block copolymer-based patterning is its ease of integration with other aspects of traditional thin-film processing, including plasma-based etching and metallization.

The CFN has been using block copolymer lithography to design the electronic and optical properties of nanostructured, thin-film materials. For example, I will describe our recent use of this approach to engineer broadband omnidirectional antireflection for solar devices. CFN
scientists work with users to design surface textures for water and fog-repellency, and able to resist water droplet impacts even in excess of 10 meters per second. Time permitting, I will show some recent progress creating nanostructured plasmonic substrates for high-sensitivity detection of molecules, which we have been using for identification of trace explosives.

Dr. Charles (Chuck) Black is a Senior Scientist and Director of the Center for Functional Nanomaterials, a national scientific user facility operated at Brookhaven National Laboratory for the US Department of Energy. Each year, the CFN supports the science of more than 500 researchers from universities, industry, and national laboratories worldwide. Prior to becoming Director, Dr. Black was Group Leader for CFN Electronic Nanomaterials, leading a research program exploring nanostructured materials for solar energy conversion. From 1996 to 2006, Dr. Black was a Research Staff Member at the IBM Thomas J. Watson Research Center in Yorktown Heights, New York. His research at IBM investigated polymer self-assembly for fabrication of high-performance semiconductor electronics. During his career, Dr. Black has also performed experimental research on ferroelectric non-volatile memories, nanocrystal-based electronic devices, superconductivity in metal nanoparticles, single-electron tunneling devices, and low-temperature scanning tunneling microscopy. Dr. Black earned the PhD degree in Physics from Harvard University in 1996, and BS degrees in Physics and Mathematics from Vanderbilt University in 1991. Dr. Black is a Member of the Board of Directors of the Materials Research Society, a Fellow of the American Physical Society, and a Senior Member of the IEEE.

11am
Haus Room, 36-428

 

February 21: Dr. Thaddeus D. Ladd

HRL Laboratories, LLC
AIsotopically Enhanced Triple-Dot Qubits in SiGe

Qubits based on silicon offer the promise of low magnetic noise due to isotopic enhancement and the availability of existing silicon growth and fabrication processes. Triple-dot qubits offer promise of exchange-only spin-qubit control, enabling operation using only gate voltages. The main impediments to silicon qubits are interface disorder, charge noise, valley degeneracy, and nuclear magnetism. In this talk, I will summarize recent data characterizing these impediments for SiGe triple dots fabricated in an undoped accumulation-mode gate architecture, including symmetric barrier control to mitigate charge noise, and isotopic enhancement to mitigate nuclear noise. I will then discuss the mathematics of pulse sequences allowing gauge-independent quantum logic, enabling future developments for exchange-only multiqubit quantum processors.

Thaddeus Ladd is a presently a senior research scientist at HRL Laboratories, LLC in Malibu, CA. Thaddeus began his Hertz-foundation-supported Ph.D. dissertation work on spin-qubit-based quantum computing implementations in the group of Yoshi Yamamoto at Stanford University in 1998. Throughout his career, he has focused on control methods and error models for spin-based qubits in solid-state materials. His thesis work included experimental dynamical decoupling sequences for silicon nuclear spins. He continued post-graduate research at Stanford, holding positions at U. Tokyo and NII, primarily focusing on ultrafast optical control of single spins in self-assembled quantum dots. Upon moving to HRL in 2009, he has worked with a team primarily considering exchange-only control of Si/SiGe quantum dots, but he continues to seek new materials and methods for better qubits.

11am
Haus Room, 36-428

 

March 21: Ken Burch

Boston College
A Weyl Route to Photovoltaics and Berry Curvature

The non-trivial evolution of wavefunctions in momentum space leads to novel phases and responses. As with any topological property, a key challenge lies in finding experiments that identify the non-local characteristics. It has recently become clear that the non-linear generation of photocurrents is directly connected to this Berry curvature, and provides a route to avoiding the hot-electron problem in photovoltaics. Weyl semimetals are particularly promising, as their non-degenerate, Dirac-like, chiral states produce diverging Berry curvature. I will describe our new approach to this problem, resulting in our observation of a room temperature, colossal Bulk PhotoVoltaic Effect in the Weyl semimetal TaAs. Due to the diverging Berry curvature, the effect is an order of magnitude larger than any previous measurement.

Dr. Burch received his Ph.D. in 2006 with D. Basov studying the IR properties of strongly correlated materials and dilute magnetic semiconductors. He then was a Director’s postdoctoral fellow at Los Alamos National Lab, where he focused on ultrafast optical studies of these same materials. In 2008 he joined the faculty at the U. of Toronto, where he established a group studying the IR, Raman and electronic transport properties of various Quantum and 2D Materials. His lab was the first to discover a high-temperature proximity effect in topological insulators and reveal evidence for Majorana fermions in a magnetic material. For this, he won the 2012 Lee-Osheroff-Richardson prize. In 2014 he joined the faculty at Boston College, where he is now an Associate Professor of Physics studying and devising new devices with various 2D, topological, superconducting and magnetic materials to reveal novel physical phenomena as well as cutting-edge biological and optical sensors.

11am
Haus Room, 36-428

 

April 4: Kurt Jacobs

ARL
Can master equations be used to model quantum computers?

Master equations provide an extremely low-cost means of modelling the effects of noise in open quantum systems, but have significant limitations. When quantum systems are controlled so as to significantly change their eigenstates and energy levels with time, there are good reasons to believe that master equations will break down. A decade ago (2006) Alicki, Lidar, and Zanardi argued that master equations could not be used to model quantum computers due to the fast timescales of the controls required to switch between different gate operations. This view appears to have been accepted by the community, and has remained unchallenged, even though no quantitative results have been obtained and master equations are still used for this purpose. Also about a decade ago, a remarkable method was developed that allows exact simulation of a system interacting with an infinite oscillator bath. We apply this method to begin to address the question of whether, and under what circumstances, master equations can model quantum computers.

Brief bio: Kurt Jacobs completed a masters and PhD with Daniel Walls and Peter Knight, respectively, and then postdocs with Salman Habib, Howard Wiseman, and Jon Dowling before joining the University of Massachusetts at Boston as an Asst. Professor in 2006. In 2015 he moved from UMass Boston to ARL (the US Army Research Laboratory) which is near DC in Maryland. He works primarily on quantum measurement and control and its applications in quantum information processing. He is the author of two books published by CUP, Stochastic Processes for Physicists, and Quantum Measurement Theory and its Applications.

11am
Haus Room, 36-428

 

April 12: W. E. Moerner

Stanford University
2018 HERMANN ANTON HAUS LECTURE
The Story of Photonics and Single Molecules, from Early FM Spectroscopy in Solids, to Super-Resolution Nanoscopy in Cells and Beyond

Reception to follow
Stata R&D Common, Fourth Floor, Building 32

4pm
Haus Room, 36-428

 

May 10: Tim Schröder

University of Copenhagen
Quantum Dot Spin-Photon Interfaces as Optical Gates in Integrated Photonic Networks

Semiconductor quantum dots have improved their optical performance dramatically in recent years, and today a clear pathway is laid out for constructing deterministic and coherent photon-emitter interfaces by embedding charged InGaAs quantum dots in photonic nanostructures [1]. Such interfaces can be employed as an on-demand single-photon source, but more generally enable deterministic quantum gates and the generation of multi-qubit entangled states of either quantum dots [2] or photons [3].

I will give an overview of our recent experimental efforts for interfacing quantum dots integrated in nanophotonic devices towards scalable systems based on these concepts. While coupling efficiencies exceeding 98% have been reported in slow light photonic crystal waveguides [4], ‘simple’ nanobeam geometries are similarly well suited: Single-photon to nanobeam waveguide coupling efficiencies of up to 95% can be achieved as demonstrated in simulation. Photons with nearly lifetime limited linewidths can be generated in such waveguides with modified width [5]. We furthermore demonstrate the coupling of several quasi-degenerate quantum emitters to a single waveguide, an important step towards the scalability of quantum dot based quantum architectures. For the efficient coupling of the generated photons to fibre networks, various out-coupling strategies are implemented.

Besides the scalable and efficient integration of quantum dots to nanostructures, coherent control of a stationary quantum bit, for example, the electron spin of a negatively charged quantum dot, is an integral requirement for the implementation of quantum information processing. Towards building quantum gates and creating spin-photon entanglement in photonic integrated circuits (PIC), we demonstrate an efficient, optically controllable interface between an electron qubit and photons guided in a PIC [6]. Resonant optical control enables a spin state preparation fidelity of up to 96% with spin state lifetimes T1 times reaching 5s, allowing for the realisation of a proof-of-concept single spin-controlled photon switch with a 4-fold switching ratio between ON and OFF states. Coherent optical control is applied to prepare arbitrary superposition states of the electron qubit integrated in a PIC.

1. P. Lodahl et al. Rev. Mod. Phys. 87, 347–400 (2015).
2. A. Delteil et al. Nat. Phys. advance online publication, (2015).
3. I. Schwartz et al. Science 354, 434–437 (2016).
4. M. Arcariet al. Phys. Rev. Lett. 113, 093603 (2014).
5. H. Thyrrestrup et al. Nano Lett. 18, 1801–1806 (2018).
6. A. Javadi et al. Nat. Nanotechnol. (2018).

4pm
Grier B, 34-401B

 

May 30: Yoshiaki Nakano

University of Tokyo
Lightwave manipulation with semiconductor photonic integrated circuits

Abstract: One of the main reasons of using lightwave for communications, sensing, imaging, and processsing is its variety in attributes. Traditionally, amplitude, phase, and wavelength have been intensively made use of in association with large capacity optical fiber communication. Polarization and mode have recently been incorporated into fiber communication so as to multiply the capacity. In association with LIDAR applications for autonomous vehicles, wavefront control has become important for beam scanning and imaging.

In this seminar talk, research activities at the University of Tokyo on optical beam steering, polarization control, and mode manipulation by making use of semiconductor photonic integrated circuits are introduced and reviewed, including integrated Stokes vector modulators/detectors on InP, reconfigurable all-optical MIMO circuits on silicon, and optical phased arrays for steering and imaging.

Biography: Yoshiaki NAKANO is professor with the Department of Electrical Engineering and Information Systems (EEIS), Graduate School of Engineering, the University of Tokyo. He is also with the Research Center for Advanced Science and Technology (RCAST), the University of Tokyo. He received the B. E., M. S., and Ph. D. degrees in electronic engineering, all from the University of Tokyo, Japan, in 1982, 1984, and 1987, respectively.

In 1987, he joined the Department of Electronic Engineering, the University of Tokyo, became an associate professor in 1992, a full professor in 2000, and the department head in 2001. He moved to RCAST, the University of Tokyo, in 2002 as a professor, and served as the Director General of the center from 2010 till 2013. Then he moved back to the Engineering School to fill up the current professorship position with the Dept. of EEIS. In 1992, he was a visiting associate professor at the University of California, Santa Barbara. Since 2010, he has also been serving as the co-director of Presidential Endowed Chair on Global Solar Plus Initiative attached direct to the University of Tokyo president office.

His research interests have been physics and fabrication technologies of semiconductor distributed feedback lasers, semiconductor optical modulators/switches, monolithically-integrated photonic circuits, and high-efficiency heterostructure solar cells, as well as metal-organic vapor phase epitaxy of III-V compound semiconductors.

11am
CUA Seminar Room, 26-214

 

July 23rd: Carlo Ottaviani

University of York
Measurement device independent quantum key distribution: from first design to high-rate modular network for quantum conferencing

Abstract: In continuous-variable (CV) measurement-device-independent (MDI) quantum key-distribution (QKD) each party sends modulated coherent state to an intermediate untrusted station (a relay) that, performing a Bell detection, establishes secret correlation between the parties, allowing them to share the secret-key. In this talk we review CV MDI-QKD, from the first design and experimental test toward the latest development. In particular, we discuss recent advancements about finite-size/composable security, the generalization to an arbitrary number of users arranged in a star-network configuration, and the design of a modular architecture based on star-network module. Our modular (lego-like) protocol resorts to a hybrid architecture where, once quantum-keys are generated for the users of each module, the shortest one can be propagated to all others users by means of iterative instances of classical one-time pad protocol. We show that our modular design may allow high-rate distribution of quantum conferencing keys among an arbitrary number of users and over arbitrary distances.

4pm
Haus Room, 36-428

 

August 6: Stephanie Wehner

QuTech, Delft University of Technology
Towards a network stack for quantum networks

Abstract: In order to realize quantum networks that can support useful applications it desirable to develop a network stack to enable reliable communication and control. Such a stack could in principle be subdivided into a number of layers similar to the classical TCP/IP stack, or OSI model. The special features of qubits (and quantum entanglement), however, introduce entirely new design challenges that are not captured by any existing model or protocol suite.

Here we present initial work towards designing such a stack. In this talk, we will in particular focus on presenting a link layer protocol, which uses a class of well known heralded entanglement generation schemes that have been realized in experiment at the physical layer.

We proceed to introduce the first discrete event simulator for quantum networks – NetSquid – and use it to investigate the performance of the link layer protocol as an example. We present initial simulation results for the link layer protocol based on a system using NV centers in diamond, for a lab setup as well as the planned test link from Delft to The Hague.

bio:
Stephanie Wehner works as Antoni van Leeuwenhoek Professor at QuTech, Delft University of Technology. Her passion is communication in all its facets, and she has written numerous scientific articles in both physics and computer science. Stephanie is one the founders of QCRYPT, which has become the largest conference in quantum cryptography. She is Roadmap Leader of the Quantum Internet and Network Computing efforts at QuTech, and is the coordinator of the european Quantum Internet Alliance. From 2010 to 2014, her research group was located at the Centre for Quantum Technologies, National University of Singapore, where she was first Assistant and later Dean’s Chair Associate Professor. Previously, she was a postdoctoral scholar at the California Institute of Technology in the group of John Preskill. In a former life, she worked in the classical internet industry and as a professional hacker

4pm
Haus Room, 36-428

 

August 7: Axel Dahlberg

QuTech, Delft University of Technology
Transforming graphs states using single-qubit operations

Abstract: Graph states are ubiquitous in quantum information with diverse applications ranging from quantum network protocols to measurement based quantum computing. Here we consider the question whether one graph (source) state can be transformed into another graph (target) state, using a specific set of quantum operations (LC+LPM+CC): single-qubit Clifford operations (LC), single-qubit Pauli measurements (LPM) and classical communication (CC) between sites holding the individual qubits. We first show that deciding whether a graph state |G> can be transformed into another graph state |G’> using LC+LPM+CC is NP-Complete, even if |G’> is restricted to be a GHZ-state. However, we also provide efficient algorithms for two situations of practical interest:

1. |G> has Schmidt-rank width one and |G’> is a GHZ-state. The Schmidt-rank width is an entanglement measure of quantum states, meaning this algorithm is efficient if the original state has little entanglement. Our algorithm has runtime O(|V(G’)||V(G)|^3), and is also efficient in practice even on small instances as further showcased by a freely available software implementation.

2. |G> is in a certain class of states with unbounded Schmidt-rank width, and |G’> is a GHZ-state of a constant size. Here the runtime is O(poly(|V(G)|)), showing that more efficient algorithms can in principle be found even for states holding a large amount of entanglement, as long as the output state has constant size.

Our results make use of the insight that deciding whether a graph state |G> can be transformed to another graph state |G’> is equivalent to a known decision problem in graph theory, namely the problem of deciding whether a graph G’ is a vertex-minor of a graph G. Many of the technical tools developed to obtain our results may be of independent interest.

4pm
Haus Room, 36-428

 

August 8: Vincenzo Tamma

U Portsmouth
Toward quantum computational and sensing supremacy based on multiphoton interference

Abstract: Multiphoton quantum interference underpins fundamental tests of quantum mechanics and quantum technologies, including applications in quantum computing, quantum sensing and quantum communication. However, standard quantum information processing schemes rely on the generation of a large number of identical photons.

In particular, scattershot boson sampling experimental demonstrations of quantum computational supremacy are challenged by the need to generate the same temporal and frequency spectra for a large number N of single photons, leading to a probability of success which scales down as the root of N and only if N^2 sources are used. Here, we employ sampling in the photonic input occupation numbers when N or more input channels are occupied to achieve for the first time a probability of success arbitrary close to one with only a linear number N of sources.

We also show how the difference in the photonic spectral properties, instead of being a drawback to overcome in experimental realisations, can be exploited as a remarkable quantum resource. Interestingly, we demonstrate how harnessing the full multiphoton quantum information stored in the photonic spectra by frequency and time resolved correlation measurements in linear interferometers enables the characterization of multiphoton networks and states, produces a wide variety of multipartite entanglement, and further scale-up experimental demonstrations of quantum computational supremacy.

References
[1] S. Laibacher and V. Tamma arXiv:1801.03832 (2018), arXiv:1706.05578 (2017)
[2] V. Tamma and S. Laibacher, Phys. Rev. Lett. 114, 243601 (2015)
[3] S. Laibacher and V. Tamma, Phys. Rev. Lett. 115, 243605 (2015)
[4] V. Tamma and S. Laibacher, Quantum Inf. Process. 15(3), 1241-1262 (2015)

11am
Haus Room, 36-428

 

August 17: Igor Aharonovich

University of Technology Sydney
Nanophotonics with Hexagonal Boron Nitride

Abstract: Engineering solid state quantum systems is amongst grand challenges in engineering quantum information processing systems. While several 3D systems (such as diamond, silicon carbide, zinc oxide) have been thoroughly studied, solid state emitters in two dimensional (2D) materials have not been observed. 2D materials are becoming major players in modern nanophotonics technologies and engineering quantum emitters in these systems is a vital goal

In this talk I will first discuss the recently discovered single photon emitters in 2D hexagonal boron nitride (hBN). I will present several avenues to engineer these emitters in large exfoliated sheets using ion and electron beam techniques. I will also discuss potential atomistic structures of the defects supported by density functional theory.

In the 2nd part of my talk I will highlight promising avenues to integrate the emitters iwht plasmonic and photonic cavities to achieve improved collection efficiency. I will show preliminary results on nanofabrication of photonic crystal cavities from layered materials and pathway for an integrated quantum photonics with 2D materials. I will summarize by outlning challenges and promising directions in the field of quantum emitters and nanophotonics with 2D materials and other wide band gap materials.

3pm
Haus Room, 36-428

 

Spring 2017

March 1: Yi-Kai Liu

National Institute of Standards and Technology
Phase Retrieval Using Unitary 2-Designs, with Applications to Quantum Process Tomography

We consider a variant of the phase retrieval problem, where vectors are replaced by unitary matrices, i.e., the unknown signal is a unitary matrix U, and the measurements consist of squared inner products |Tr(C*U)|^2 with unitary matrices C that are chosen by the observer. This problem has applications to quantum process tomography, when the unknown process is a unitary operation.
We show that PhaseLift, a convex programming algorithm for phase retrieval, can be adapted to this matrix setting, using measurements that are sampled from unitary 4- and 2-designs. In the case of unitary 4-design measurements, we show that PhaseLift can reconstruct all unitary matrices, using a near-optimal number of measurements. This extends previous work on PhaseLift using spherical 4-designs.
In the case of unitary 2-design measurements, we show that PhaseLift still works pretty well on average: it recovers almost all signals, up to a constant additive error, using a near-optimal number of measurements. These 2-design measurements are convenient for quantum process tomography, as they can be implemented via randomized benchmarking techniques. This is the first positive result on PhaseLift using 2-designs.
(This is joint work with Shelby Kimmel.)

Yi-Kai Liu is a computer scientist at the US National Institute of Standards and Technology (NIST), and a Fellow at the Joint Center for Quantum Information and Computer Science (QuICS) at the University of Maryland. He specializes in quantum computation and cryptography. He has worked on the design of tamper-resistant quantum devices, compressed sensing methods for quantum tomography, quantum algorithms based on wavelet transforms, and the computational complexity of quantum chemistry. He received his PhD in computer science at the University of California in San Diego in 2007, and was a postdoctoral researcher at Caltech and UC Berkeley until 2011, when he moved to NIST.

11am
Haus Room, 36-428

 

March 8: Jens Koch

Northwestern University
Parametric modulation and sidebands in circuit QED — from red to blue, and on to “purple”

Superconducting circuits rank among the top contestants in the pursuit of scalable quantum information processing. Indeed, remarkable advances in quantum engineering of circuit QED systems have led to an increase in coherence times of 5 orders or magnitudes in these Josephson junction based devices. At the same time, exquisite control via microwaves has enabled the demonstration of high-fidelity 1- and 2-qubit gates now approaching the quantum error correction threshold. I will review how quantum mechanics manifests in these circuits, enabling exciting studies in quantum optics and quantum information processing. The talk’s main part will focus on our recent theory work investigating parametric modulation and sideband physics in these systems – where simultaneously driving of red and blue sidebands may allow for stabilization of qubit states along any desired axis of the Bloch sphere.

Jens Koch is an Associate Professor of Physics at Northwestern University. His research focuses on superconducting qubits and circuit QED for quantum simulation and quantum computation. He received his Ph.D. from Freie Universitat Berlin in 2006 under supervision of Felix von Oppen. In 2006, he received a Yale Postdoctoral Prize Fellowship and worked as a Postdoctoral Associate in Steven Girvin’s group before moving to Northwestern University in 2010.

11am
Haus Room, 36-428

 

March 29: Liang Jiang

Yale University
Quantum Control & Quantum Error Correction with Superconducting Circuits

We have developed an efficient quantum control scheme that allows for arbitrary operations on a cavity mode using strongly dispersive qubit-cavity interaction and time-dependent drives [1,2]. In addition, we have discovered a new class of bosonic quantum error correcting codes, which can correct both cavity loss and dephasing errors [3]. Our control scheme can readily be implemented using circuit QED systems, and extended for quantum error correction to protect information encoded in bosonic codes [4]. Moreover, engineered dissipation can also implement holonomic quantum computation using superconducting circuits [5,6].
[1] Krastanov, et al., PRA 92, 040303 (2015)
[2] Heeres, et al., PRL 115, 137002 (2015)
[3] Michael, et al., PRX 6, 031006 (2016)
[4] Ofek, et al., Nature 536, 441 (2016)
[5] Albert, et al., PRL 116, 140502 (2016)
[6] Albert, et al., PRX 6, 041031 (2016)

Liang Jiang is an assistant professor of Applied Physics and Physics at Yale University. He obtained his B.S. from Caltech in 2004 and Ph.D. from Harvard in 2009. As a theorist, he investigates various quantum systems and explores applications of quantum information. He has developed various quantum repeater protocols for long distance quantum communication and explored room-temperature diamond-based quantum sensing and information processing. Recently, Liang has been investigating quantum information processing with superconducting circuits with ultra-strong couplings and unprecedented non-linearity of microwave photons. Liang is a recipient of the Alfred P. Sloan Research Fellowship, and the David and Lucile Packard Foundation Fellowship in 2013.

11am
Haus Room, 36-428

 

March 29: Neil Sinclair * Additional special seminar at 3pm!

University of Calgary
Rare-earth-ion-doped crystals for future quantum technology

Rare-earth-ion-doped crystals have long been known to possess many favorable properties at cryogenic temperatures. This has spurred the development of these crystals for various applications of quantum science, with particular emphasis on quantum memories for quantum repeaters. In this presentation, I summarize the research being performed using rare-earth-ion-doped crystals at the Quantum Cryptography and Communication Laboratory in Calgary, Canada.
I will discuss work employing a thulium-doped lithium niobate waveguide. We have recently shown that this waveguide, which is fabricated by the indiffusion of titanium into thulium-doped lithium niobate, has spectroscopic properties that are equivalent to those of a similar unmodified bulk crystal. These results refute previously held beliefs that crystal modification comes at the expense of deteriorated properties. Next I outline a scheme for quantum repeaters that benefits from the large bandwidths provided by the inhomogeneous broadening of rare-earth-doped ensembles and show results from a proof-of-principle experiment using the thulium-doped lithium niobate waveguide. Furthermore, I illustrate how this waveguide could be used to perform quantum signal processing tasks, including quantum non-destructive measurements of qubits.
Finally, I discuss work towards a quantum memory at 795 nm that features storage times of hundreds of microseconds, an experiment where we demonstrate entanglement between more than two hundred ensembles of rare-earth ions, and the development of the first waveguide quantum memory at telecom wavelength.

Neil obtained his B.Sc. from the University of Waterloo, and recently his Ph.D. from the University of Calgary under the guidance of Wolfgang Tittel. Neil’s research involves the development of rare-earth-ion-doped crystals towards the realization of quantum science and technology, with focus on long-distance secure communication networks.

3pm
Grier B, 34-401B

 

April 26, THE HERMANN ANTON HAUS LECTURE: William D. Phillips

Nobel Laureate; National Institute of Standards and Technology, Gaithersburg
Manipulating Atoms with Light: from Spectroscopy to Atomtronics

4pm
RLE Conference Center: Hermann Anton Haus and Jonathan Allen Rooms 36-428/36-462
Open to the Public

Reception to follow
Grier Rooms A & B, Fourth Floor, Building 34

 

May 24: Oliver Pfister

University of Virginia
Engineering noninteracting-boson fields: from squeezed measurement noise to large-scale entanglement for continuous-variable quantum computing

Quantum optics may be viewed as the optics of manifestly nonclassical waves, e.g. matter waves, and may also be understood as the nonclassical optics of any wave. The latter definition is more universal as it involves the quantum effect of particle statistics on wave interference, with a central role played by vacuum field modes. In this seminar, I will present several quantum optics experiments in which photon statistics are altered, or squeezed, away from the vacuum noise, for 1 to 60 modes of the same optical parametric oscillator. Squeezing can then be directly applied to secure communication, high-precision interferometry, and the generation of arbitrary-size cluster states. Such states are suitable for continuous-variable quantum computing, for which a fault tolerance threshold was recently proven to exist.

Olivier Pfister received a B.S. in Physics from Université de Nice, France, in 1987, and a Ph.D. in Physics from Université Paris-Nord, France, in 1993. He was a research associate with John L. Hall at JILA, University of Colorado (1994-7) and with Daniel J. Gauthier at Duke University (1997-9). He then joined the University of Virginia faculty, where he is now a professor of physics. His current research interests are experimental quantum computing with quantum fields and quantum optical measurements at the ultimate precision. Olivier Pfister is a fellow of the American Physical Society.

4pm
Haus Room, 36-428

 

August 3: Alex Neville

University of Bristol
No imminent quantum supremacy by boson sampling

Boson sampling is a computational problem that has been proposed as a near-term route to achieving ‘quantum computational supremacy’ via a linear optical experiment. A serious comparison between the best quantum and classical approaches to the problem has been missing however. Using a Markov chain Monte Carlo approach we show that 30 photon, 900 mode experiments can be simulated on a laptop in a matter of minutes. We predict that in order to perform dramatically better than current supercomputers, a future experiment will require high efficiency preparation of >50 photon states and low loss interferometers with several thousand optical modes and detectors.

11am
Haus Room, 36-428

 

August 7: Frank Koppens

ICFO-The Institute of Photonic Sciences
The ultimate quantum limit of plasmonic confinement in 2d material heterostructures

4pm
Allen Room, 36-462

 

August 23: Stefano Pirandola

University of York
Repeater-assisted quantum and private capacities

We consider quantum communications assisted by repeaters, from the basic scenario of a single repeater chain to the general case of an arbitrarily-complex quantum network, where systems may be routed through single or multiple paths. In this context, we investigate the ultimate rates at which two end-parties may transmit quantum information, distribute entanglement, or generate secret keys. These end-to-end capacities are defined by optimizing over the most general adaptive protocols that are allowed by quantum mechanics. Combining techniques from quantum information and classical network theory, we derive single-letter upper bounds for the end-to-end capacities in repeater chains and quantum networks connected by arbitrary quantum
channels, establishing exact formulas under basic decoherence models, including bosonic lossy channels, quantum-limited amplifiers, dephasing and erasure channels. For the converse part, we adopt a teleportation-inspired simulation of a quantum network which leads to upper bounds in terms of the relative entropy of entanglement. For the lower bounds we combine point-to-point quantum protocols with classical network algorithms. Depending on the type of routing (single or multiple), optimal strategies corresponds to finding the widest path or the maximum flow in the quantum network. Our theory can also be extended to simultaneous quantum communication between multiple senders and receivers.
Based on
https://arxiv.org/abs/1601.00966

11am
Allen Room, 36-462

 

Fall 2016

October 12: Daniel Stick

Sandia National Laboratories
Surface ion traps for quantum computing

Over the last decade micro­fabricated surface ion traps have evolved from a novelty technology to one that is potentially capable of supporting scalable quantum information processing. In this talk I will describe the technologies we have added to our ion traps to support this progression, including the ability to make traps with arbitrary 2D geometries and optical access for high power laser beams. I will describe the classical experiments we have performed which are components of operating a logical qubit, as well as single and two qubit gate experiments where we achieve process fidelities of 99.99% and 99.5%, respectively.

Dr. Daniel Stick is a Principal Member of Technical Staff at Sandia National Labs (SNL). His research focuses on designing and testing micro­fabricated surface ion traps for their suitability for quantum information applications, including storing, transporting, and performing quantum gates on ions. Dr. Stick received his BS from Caltech and his PhD from the University of Michigan. He was the recipient of a 2012 Presidential Early Career Award for Scientists and Engineers (PECASE) for his research in trapped ion quantum computing.

11am
Haus Room, 36-428

 

October 17: Benjamin Eggleton * Note the change to Monday this week!

University of Sydney
Inducing and harnessing sound-light interactions in nanoscale integrated circuits

One of the surprises of nonlinear optics – the field of optics with high intensity lasers – is that light may interact strongly with sound, the most mundane of mechanical vibrations. Intense laser light literally “shakes” the glass in optical fibres, exciting acoustic waves (sound) in the fibre. Under the right conditions, it leads to a positive feedback loop between light and sound termed “Stimulated Brillouin Scattering,” or simply SBS. This nonlinear interaction can amplify or filter light waves with extreme precision in frequency (colour) which makes it uniquely suited to solve key problems in the fields of defence, biomedicine and wireless communications amongst others. We recently achieved the first demonstration of SBS in compact chip-scale structures, carefully designed so that the optical fields and the acoustic fields are simultaneously confined and guided. This new platform has opened a range of new chip-based functionalities that are being applied in communications and defence with record performance and compactness. This new optical-phononic chip reveals new regimes of light sound interactions at the nanoscale, which has required new theoretical developments. My talk will introduce this new field, review our progress and achievements and recent highlights that point towards a new class of entirely silicon based optical phononic processor that can be manufactured in semiconductor CMOS foundries.

Professor Benjamin Eggleton is an ARC Laureate Fellow and Professor of Physics at the University of Sydney and Director of the ARC Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS). He obtained his PhD degree in Physics from the University of Sydney, in 1996 and then joined Bell Laboratories, Lucent Technologies as a Postdoctoral Member of Staff. In 2000, he was promoted to Director within the Specialty Photonics Division of Bell Laboratories, where he was engaged in forward-looking research supporting Lucent Technologies business in optical fiber devices. He returned to the University of Sydney in 2003 as the founding Director of CUDOS and Professor in the School of Physics.Professor Eggleton is a Fellow of the Australian Academy of Science, the Optical Society of America, IEEE Photonics and the Australian Technology, Science and Engineering Academy (ATSE). He was the recipient of the 2011 Eureka Prize for Leadership in Science, the Walter Boas Medal of the Australian Institute of Physics and the OSA’s Adolph Lomb Medal. Eggleton has published about 440 journal papers which have been cited >15,000 times with an h-number of > 60 (webofscience). He was President of the Australian Optical Society, is currently Editor-in-Chief for APL Photonics and serves on the Board of Governors for IEEE Photonics.

11am
Haus Room, 36-428

 

October 27: Mehul Malik * Note the change to Thursday this week!

Institute for Quantum Optics and Quantum Information (IQOQI) Vienna, Austria
Multi-photon entanglement in high dimensions

Entanglement lies at the heart of quantum mechanics—as a fundamental tool for testing its deep rift with classical physics, while also providing a key resource for quantum technologies such as quantum computation and cryptography. In 1987 Greenberger, Horne, and Zeilinger realized that the entanglement of more than two particles implies a non-statistical conflict between local realism and quantum mechanics. Experimental efforts since have singularly focused on increasing the number of particles entangled, while remaining in a two-dimensional space for each particle. Here we show the experimental generation of the first multi-photon entangled state where both—the number of particles and the number of dimensions—are greater than two. Interestingly, our state exhibits an asymmetric entanglement structure that is only possible when one considers multi-particle entangled states in high dimensions. Two photons in our state reside in a three-dimensional space, while the third lives in two dimensions. Our method relies on combining two pairs of photons, high-dimensionally entangled in their orbital angular momentum, in such a way that information about their origin is erased. Additionally, we show how this state enables a new type of “layered” quantum cryptographic protocol where two parties share an additional layer of secure information over that already shared by all three parties. In addition to their application in novel quantum communication protocols, such asymmetric entangled states serve as a manifestation of the complex dance of correlations that can exist within quantum mechanics.

Dr. Mehul Malik is a senior post-doctoral fellow in the group of Professor Anton Zeilinger at the Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna, Austria. Originally from New Delhi, India, Mehul received his PhD in Optics in 2013 from the University of Rochester under the supervision of Professor Robert Boyd, and a Bachelor of Arts in 2006 from Colgate University. He is currently working on experimental multi-photon quantum entanglement and high-dimensional quantum states of light. His broader research interests lie in the fields of fundamental quantum optics, quantum imaging, and quantum information.

11am
Haus Room, 36-428

 

November 2: Duncan Steel

University of Michigan
Optical control of electronic and nuclear states: Toward quantum computing in self-assembled dots

The optical properties of semiconductor quantum dots is dramatically and physically different from higher dimensional materials. The results, including the ability to deterministically optically switch the electronic states, allow for photonic devices that were not remotely possible before. While their behavior is much more like isolated atoms, there are many features that remain quite distinct and not totally understood at this point because dots are comprised of order 104 atoms and hence remain many body systems. In the case of nuclear coupling, the results include new physical behavior. In this talk, I will review some of the key features that are creating excitement in these structures for application in quantum information as well as discuss the observation of metastable mesoscopic nuclear states with glassy like properties.

11am
Haus Room, 36-428

 

November 9: Kartik Srinivasan

National Institute of Standards and Technology
Chip-Based Signal Transducers Using Nanophotonics

Advances in nanofabrication have enabled the development of photonic geometries that can control the propagation and confinement of optical waves at the wavelength-scale. This complements similar developments in other domains, for example, decades-long efforts at manipulating charge carriers in micro- and nano-electronic devices, and the engineering of acoustic waves in nanomechanical systems. Taken together, there is great opportunity to develop systems in which the strength of light-matter interactions is dramatically increased in comparison to bulk materials, enabling the coherent coupling between photons and other information carriers, such as phonons, excitons, or photons of another color. Our lab has been developing such nanophotonic transducers in a variety of contexts, for applications in photonic quantum information science, communications, and metrology. In this talk, I will present an overview of the design, fabrication, and measurement of different chip-scale signal transducers based on the engineering of nonlinear optical, optomechanical, and dipole interactions in nanoscale geometries. Representative devices include efficient and ultra-low- noise optical frequency converters, octave-spanning microresonator frequency combs, piezo-optomechanical circuits, and single-photon sources based on single quantum dots.

Kartik Srinivasan is a Project Leader at the NIST Center for Nanoscale Science and Technology (CNST). He received B.S., M.S., and Ph.D. degrees in Applied Physics from the California Institute of Technology, where his graduate research was supported by a Fannie and John Hertz Foundation Fellowship. At the CNST, he leads projects in the field of nanophotonics, with a current focus on topics in photonic quantum information science, nonlinear optics, and optical sensors. He has been awarded the NIST Sigma Xi Young Scientist Award, the Presidential Early Career Award for Scientists and Engineers, and the US Department of Commerce Bronze Medal.

11am
Haus Room, 36-428

 

November 16: Ken Brown

Georgia Tech
Quantum Computing with Trapped Ions

Quantum computation promises an exponential algorithmic speed up over classical computation. Currently quantum computing hardware is limited by errors in the control and unwanted interactions with the environment. I will present our theoretical and experimental work on removing both control and algorithmic errors in ion trap quantum processors. I will also discuss proposals for scaling ion trap quantum computers from 10’s to 100’s of qubits.

11am
Haus Room, 36-428

 

November 23: Hong-Gyu Park

Korea University
Subwavelength-scale novel nanophotonic devices

In this talk, I will present three topics, (1) electrically driven nanolasers, (2) plasmonic lasers and tweezers, and (3) nanowire photovoltaics. First, I will talk about electrically driven photonic crystal lasers and graphene-contact microdisk lasers: an electrically driven 1D nanobeam laser with a footprint approaching the smallest possible value [1] and an electrically driven microdisk laser using a transparent graphene electrode [2] were successfully demonstrated. Second, I will present an optically pumped silver-nanopan plasmonic laser with a subwavelength mode volume of 0.56(λ/2n)3 [3] and low-power nano-optical vortex trapping using plasmonic resonance in gold diabolo nanoantennas [4]. Finally, I will present single-crystalline silicon nanowire photovoltaic devices that show high open-circuit voltages and short-circuit current densities, and ultralow leakage currents [5]. Also, an efficient way to tune and enhance light absorption in nanowire photovoltaics will be presented [6]. I believe that our progress in demonstrating subwavelength nanophotonic devices represents an important step toward further miniaturization of coherent light sources as well as fast all-optical processing in an ultracompact photonic integrated circuit.
[1] K.-Y. Jeong et al., Electrically driven nanobeam laser, Nature Commun. 4, 2822 (2013).
[2] Y.-H. Kim et al., Graphene-contact electrically driven microdisk lasers, Nature Commun. 3, 1123 (2012).
[3] S.-H. Kwon et al., Subwavelength plasmonic lasing from a semiconductor nanodisk with silver nanopan cavity, Nano Lett. 10, 3679 (2010).
[4] J.-H. Kang et al., Low-power nano-optical vortex trapping via plasmonic diabolo nanoantennas, Nature Commun. 2, 582 (2011).
[5] S.-K. Kim et al., Tuning light absorption in core/shell silicon nanowire photovoltaic devices through morphological design, Nano Lett. 12, 4971 (2012).
[6] S.-K. Kim et al., Doubling absorption in nanowire solar cells with dielectric shell optical antennas, Nano Lett. 15, 753 (2015).

Hong-Gyu Park received his PhD in Physics at Korea Advanced Institute of Science and Technology (KAIST) in 2004. He was a post-doctoral fellow in the lab of Professor Charles M. Lieber at Harvard University from 2005 to 2007. In 2007, he joined the Department of Physics at Korea University, where he is currently a full professor and a director of Center for Subwavelength Nanowire Photonic Devices. His research interests include multifunctional subwavelength plasmonic devices and efficient semiconductor nanowire photovoltaics.

11am
Haus Room, 36-428

 

December 21: Dmitry Budker * Note the change to 3pm this week!

UC Berkeley
Atomic and color-center magnetometry in the lab, in the field, and in the sky

3pm
Grier A, 34-401A

 

Spring 2016

February 24: Edo Waks

University of Maryland
Quantum nanophotonics: controlling light with a single quantum dot

Interactions between light and matter lie at the heart of optical communication and information technology. Nanophotonic devices enhance light-matter interactions by confining photons to small mode volumes, enabling optical information processing at low energies. In the strong coupling regime, these interactions are sufficiently large that a single photon creates a nonlinear response in a single atomic system. Such single-photon nonlinearities are highly desirable for quantum information processing applications where atoms serve as quantum memories and photons act as carriers of quantum information. In this talk I will discuss our effort to develop and coherently control strongly coupled nanophotonic devices using quantum dots coupled to photonic crystals. Quantum dots are semiconductor “artificial atoms” that can act as efficient photon emitters and stable quantum memories. By embedding them in a photonic crystal cavity that spatially confines light to less than a cubic wavelength we can attain the strong coupling regime. This device platform provides a pathway towards compact integrated quantum devices on a semiconductor chip that could serve as basic components of quantum networks and distributed quantum computers. I will discuss our demonstration of a quantum transistor, the fundamental building block for quantum computers and quantum networks, using a single electron spin in a quantum dot [1,2]. I will then describe a realization of a new cavity QED approach to measure the state of a spin all-optically. This technique enables efficient spin readout even when the spin has a poor cycling transition. Finally, I will discuss our recent effort to extend our results into the telecommunication wavelengths, and to improve the efficiency and scalability of the structure in order to attain integrated multi-dot devices on a single chip.
[1] Kim, H., R. Bose, T.C. Shen, G.S. Solomon, and E. Waks, A quantum logic gate between a solid-state quantum bit and a photon. Nat Photon, 2013. 7 (5): p. 373-377. Available from:
http://dx.doi.org/10.1038/nphoton.2013.48.
[2] Sun, S., H. Kim, G.S. Solomon, and E. Waks, A quantum phase switch between a single solid-state spin and a photon. Nat Nano, 2016. advance online publication. Available from: http://dx.doi.org/10.1038/nnano.2015.334.

11am
Haus Room, 36-428

 

March 9: Saikat Guha

Raytheon BBN
Quantum Limits of Optical Communication

The theme of my talk will be the fundamental quantum-mechanics-driven limits to the rate at which information can be encoded and transmitted reliably over an optical communication channel, with applications to fiber-based and free space communications. We will first discuss the quantum limits of reliable communication with no requirement on security of the communicated data, and then discuss how the reliable-communication limits change when we impose an additional requirement that the communicated data is kept secure from being decoded by the worst-case adversary allowed by quantum mechanics. I will discuss how one can surpass the aforesaid rate limit of quantum-secure communication by using quantum repeaters–special-purpose quantum processors inserted along the length of the optical channel. Finally, I will talk about the fundamental limits of reliable communications when not only the message content, but the communication attempt itself must also be kept hidden (or, covert) from being detected by the worst-case adversary allowed by quantum mechanics. Throughout my talk, I will discuss the quantum information theoretic limits to communications, as well as known results and open problems on how one could construct structured optical transmitters, receivers and protocols to bridge the gaps between those limits and the best performance achievable using conventional optical components.

11am
CUA Seminar Room, 26-214

 

March 16: Jason S. Orcutt

IBM Thomas J. Watson Research Center
CMOS Hacking

Modern CMOS processes have benefitted from decades of engineering and investment. The intended application of all of this technology is manufacturing large-scale electronic circuits, but many new applications can be enabled at a designer level by controlling the mask layers or at a foundry level by adding process modules. I will discuss both methodologies with a focus on my experiences hacking CMOS manufacturing processes into platforms for integrated photonics. I will also discuss the monolithic CMOS silicon photonics technology, known as CMOS9WG, that was developed at IBM to target the datacom market. The expected volume of this market has motivated a process that is highly customized for integrated photonic devices and packaging. Now these nanophotonic building blocks, diverse process features and rich CAD enablement can be leveraged to be applied to an even more diverse set of applications from environmental trace gas sensing to quantum communication.

11am
Haus Room, 36-428

 

March 30: Ryan Hamerly

Stanford University
Quantum Noise in Photonic Logic: from Free Carriers to Ising Machines

As nanophotonics and materials research drive optical logic to the low-power, few-photon limit, quantum properties of light start to matter. Even if we aren’t building a quantum computer, these quantum effects can play a key role limiting the performance of existing devices, or enabling entirely new dynamics. I present quantum simulations of devices based on semiconductor (free-carrier) optical nonlinearities and propose an optical annealing machine based on this effect. In addition, I apply these methods to study synchronously-pumped optical parametric oscillator (OPO) networks, which have recently been proposed and demonstrated, and are a promising alternative to digital computers for Ising optimization problems.

11am
Haus Room, 36-428

 

April 6: William Oliver

MIT and MIT Lincoln Laboratory
Quantum Information Science with Superconducting Qubits

Superconducting qubits are coherent artificial atoms assembled from electrical circuit elements and microwave optical components. Their lithographic scalability, compatibility with microwave control, and operability at nanosecond time scales all converge to make the superconducting qubit a highly attractive candidate for the constituent logical elements of a quantum information processor. In this talk, we revisit the design, fabrication, and control of the superconducting flux qubit. By adding a high-Q capacitor, we dramatically improve its reproducibility, coherence, and anharmonicity. We discuss in a detail a device with T1 = 55 us. We identify quasiparticles as causing temporal variability in the T1, and we demonstrate the ability to pump these quasiparticles away to stabilize and improve T1. The Hahn echo time T2E = 40 us does not reach the 2T1 limit. We demonstrate that this limitation results from dephasing caused by the shot noise of residual thermal photons in the readout resonator. We then use CPMG dynamical decoupling to recover T2CPMG ~ 2T1 in a manner consistent with the noise spectrum.

11am
Haus Room, 36-428

 

April 20, THE HERMANN ANTON HAUS LECTURE: Keren Bergman

Columbia University
Computing at the Speed of Light: How Optical Data Movement Will Transform Future Systems

4pm
RLE Conference Center: Hermann Anton Haus and Jonathan Allen Rooms 36-428/36-462
Reception following the Lecture

Fall 2015

September 23: Mete Atature

University of Cambridge
Properties and Applications of Coherent Photons from Quantum Dots

Quantum dots and atomic impurities in solids provide opportunities for a range of activities within the umbrella of quantum-related research. Their inherently mesoscopic nature leads to a multitude of interesting interaction mechanisms of confined spins with the solid state environment of spins, charges, vibrations and light. Implementing a high level of control on these constituents and their interactions with each other creates exciting opportunities for realizing stationary and flying qubits within the context of spin-based quantum information science. I will provide a snapshot of the progress and challenges for optically interconnected spins, as well as first steps towards hybrid distributed quantum networks involving other physical systems. I will also present how progress on the technical aspects can lead to research in fundamental concepts.

11am
Haus Room, 36-428

 

October 14: Philip Kim

Harvard University
Electronic and Optoelectronic Physics in the van der Waals Heterojunctions

Recent advance of van der Waals (vdW) materials and their heterostructures provide a new opportunity to realize atomically sharp interfaces in the ultimate quantum limit. By assembling atomic layers of vdW materials, such as hexa boronitride, transition metal chalcogenide and graphene, we can construct novel quantum structures. Unlike conventional semiconductor heterostructures, charge transport of the devices are found to critically depend on the interlayer charge transport, electron-hole recombination process mediated by tunneling across the interface. We demonstrate the enhanced electronic optoelectronic performances in the vdW heterostructures, tuned by applied gate voltages, suggesting that these a few atom thick interfaces may provide a fundamental platform to realize novel physical phenomena, such as hydrodynamic charge flows, cross-Andreev reflection across the quantum Hall edges states, and interlayer exciton formation and manipulations.

11am
Haus Room, 36-428

 

November 5: Eli Kapon

École polytechnique fédérale de Lausanne
Quantum Photonics with Ordered Quantum Dot and Quantum Wire Systems

Quantum wire (QWR) and quantum dot (QD) systems offer means for tailoring the electronic structure of semiconductors thanks to multi-dimensional quantum confinement. By placing them in confined photonic structures (waveguides, cavities) it is possible to tailor light-matter interaction via the introduced modifications in the density of states of excitons and photons. We review the technology of ordered QWR and QD structures grown by metallolrganic vapor phase epitaxy on patterned substrates and their integration with photonic components. Tailoring exciton wavefunctions, controlling their recombination dynamics, and observing cavity quantum electrodynamic effects in the integrated structures are described. Applications in quantum information technology and ultralow threshold lasers are discussed.

11am
Haus Room, 36-428

 

November 18: Miloš A. Popović

University of Colorado at Boulder
From the Complex Plane to Complex Photonic Circuits

Four decades on from the pioneering first steps at Bell Labs, microphotonics is at a transition from a few components to large-scale integrated systems on chip. In the near term, this means improvements to complex electronic systems through integration with relatively simple photonic systems. But in the longer term, it also means complex passive, active and nonlinear photonic structures with novel functions will become practical and may enable a new generation of integrated systems-on-chip. With the end of Dennard scaling of the transistor bringing Moore’s Law to a grinding halt, power and communication have become critical drivers for microelectronics, connected problems addressable by photonics. In the first part of my talk, I will describe recent results on photonic device technology engineered within advanced-node CMOS microelectronics that has enabled millions of transistors and thousands of photonic devices to coexist and produce record-energy optical transmitters, receivers and chip-to-chip optical links, on the way to an optically interfaced microprocessor. In the second part of my talk, I will address how CMOS integration has spawned new device technology challenges and opportunities. Free electronic control of otherwise ultrasensitive photonics opens the door to robust large scale photonic circuits and enables device-level design that admits complex photonic “element circuits”. In this context, I will talk about fundamental limits of modulators and breaking their speed-energy tradeoff; the “dark state laser” concept that leverages imaginary coupling, a new type of coupling mechanism; and applying “photonic circuit” concepts to nonlinear and quantum optics to control the coherence of light.

11am
Haus Room, 36-428

 

December 2: Christoph Becher

Universität des Saarlandes, Saarbrücken, Germany
Interfacing color centers in diamond with (telecom) photons

The coupling of single color centers in diamond to photons, providing an efficient spin-readout, is considered an important step towards integrated solid-state devices for quantum information processing and quantum sensing. For interfacing to photons I will present two routes for the deterministic coupling of single nitrogen- (NV) or silicon-vacancy (SiV) centers to optical cavities at the micro- and nano-scale using either fiber-based, tunable, Fabry-Perot-type resonators [1] or photonic crystal cavities directly fabricated in the diamond material. We observe channeling of the spontaneous emission into the cavity modes [2,3], paving the way for high-speed single photon sources and optical interfaces for quantum information. Long-range transmission in quantum networks, in addition, requires photons at telecommunication wavelengths, offering minimal loss in optical fiber links. As color centers in diamond (NV, SiV) emit in the visible to near-infrared range, techniques are necessary to bridge the gap between their emission and the telecom spectral regions. I will present experimental approaches for interfacing single emitters such as trapped ions, semiconductor quantum dots or color centers with telecom photons, based on quantum frequency conversion [4].
[1] R. Albrecht et al., Phys. Rev. Lett. 110, 243602 (2013).
[2] J. Riedrich-Möller et al., Nano Lett. 14, 5281 (2014).
[3] J. Riedrich-Möller et al., Appl. Phys. Lett. 106, 221103 (2015).
[4] S. Zaske et al., Phys. Rev. Lett. 109, 147404 (2012).

11am
Haus Room, 36-428

 

December 9: Jacques Carolan

University of Bristol
Universal linear optics: characterisation, verification and computation

Photonic approaches to quantum information science and technology promise new scientific discoveries and new applications. Linear optics underpins all of these protocols and the advent of integrated quantum photonics has has brought with it a step change in complexity and control over quantum photonic systems. In this talk we demonstrate a single reprogrammable optical circuit that is sufficient to implement all possible linear optical protocols up to the size of that circuit. We present techniques for machine level characterisation and in situ verification of computational tasks; and programme the system to implement heralded quantum logic and entangling gates, hundreds of instances of boson sampling and six-dimensional complex Hadamards. Linear optical processors with the ability to arbitrarily “dial up” such operations serve as a testbed to rapidly develop new linear optical protocols, pointing the way to applications across fundamental science and quantum technologies.

11am
Haus Room, 36-428

 

Spring 2015

March 11: Ronald Walsworth

Harvard University & Smithsonian Institution
Nanoscale Magnetic Imaging Using NV-Diamond

I will provide an overview of nanoscale magnetic sensing and imaging using atom-like Nitrogen-Vacancy (NV) quantum defects in diamond. NV-diamond provides an unprecedented combination of magnetic field sensitivity and spatial resolution in a room-temperature solid due to the remarkable properties of NV centers, including long electronic spin coherence times, optical spin polarization and read-out, a large Zeeman shift of the spin transitions, and the robust physical properties of diamond in a wide variety of forms (bulk crystals, films, nanocrystals, etc.). Promising applications include sensing and quantum control of individual electron and nuclear spins, imaging of magnetic fields from biological cells under ambient conditions, and studies of magnetic materials of wide-ranging relevance from Earth science to condensed matter physics to brain science.

11am
Haus Room, 36-428

 

March 18: Philip Mauskopf

Arizona State University
Applications of Single Photon Detectors in Astronomy

The field of experimental quantum optics can be traced back to the pioneering experiments of Hanbury-Brown and Twiss who measured correlations in the detected intensity fluctuations of photons arriving at two detectors observing the same source. They used this effect to make the first direct measurements of the diameters of stars in the 1950s. However, after that, the technique of “intensity interferometry” in astronomy to resolve objects was set aside in favor of field combining interferometry because field combining had the potential for improved signal to noise ratios for a given aperture size and also gave a complex visibility rather than a visibility magnitude only. However, it then took decades for field combining interferometers to overcome the technical challenges of combining beams from separated telescopes well enough to catch up with the original intensity interferometry measurements. During this time, single photon detectors improved in both wavelength coverage and time resolution. Now, several groups are investigating reviving the field of intensity interferometry to make astronomical measurements that are impossible with other current techniques. I will describe some of these measurements and the prospects for a new era of “quantum astronomy” with single photon detectors.

11am
Haus Room, 36-428

 

April 1: R.M. Osgood, Jr.

Columbia University
Mid-IR nonlinear integrated silicon photonics

After some brief comments on my many years of involvement with lasers and laser applications at MIT, I discuss our recent developments using silicon nanophotonic wires as nonlinear media at mid-IR wavelengths both to observe nonlinear optical physics and to explore specific applications. The discussion will include motivation and potential application areas, basic nonlinear physics, observation of high optical gain, advances in select device areas including IR detectors. Much of this work was carried out as joint projects with IBM (Will Green), Bergman Group at Columbia, and MIT Lincoln Lab (Mike Geis).

11am
Haus Room, 36-428

 

April 8: Shu-Wei Huang

University of California, Los Angeles
Generation and stabilization of optical frequency comb from on-chip microresonators

The current benchmark laser systems for optical frequency combs are self-referenced femtosecond mode-locked lasers. However, continuous-wave pumped microresonators recently emerge as promising alternative platforms for optical frequency comb generation. Microresonator-based optical frequency combs, or Kerr frequency combs, are unique in their compact footprints and offer the potential for monolithic electronic and feedback integration, thereby expanding the already remarkable applications of optical frequency combs. In this talk, I will report two recent progresses on optical frequency combs from on-chip Si3N4 microresonators: 1) generation of mode-locked ultrashort pulses from a ring resonator; and 2) stabilization of 18 GHz Kerr frequency comb from a spiral resonator. I will first describe the generation of stable mode-locked pulse trains from normal dispersion microresonators. The importance of pump detuning and wavelength-dependent quality factors in stabilizing and shaping the pulse structure will be discussed. Then I will present a low-phase-noise Kerr frequency comb with 18 GHz comb spacing, compatible with high-speed silicon optoelectronics. Both the pump frequency and the comb spacing can be stabilized using standard phase locked loop technique.

11am
Haus Room, 36-428

 

April 15: Yoav Lahini

MIT
Guided-wave optics: from quantum simulations to sensing single viruses

Integrated networks and arrays of coupled optical waveguides offer a powerful toolbox for the high fidelity and robust control of the flow of classical and quantum light. I will discuss how this approach enabled the simulation of quantum walks – the quantum mechanical analogue of classical random walks – which were used to study transport in nonlinear disordered media and to implement new schemes for the manipulation and processing of quantum information. I will then describe the construction of a novel nanofluidic guided-wave microscope, capable of tracking freely diffusing, unlabeled nanoparticles and even single viruses down to 20 nanometers in size at kilohertz rates. I will end with describing our current push to even higher sensitivity, in an effort to open a path for the study of fast biological and non-biological processes at the nanoscale.

11am
Haus Room, 36-428

 

April 22, THE HERMANN ANTON HAUS LECTURE: Andrew Weiner

Purdue University
Ultrafast and Broadband Photonic Signal Processing

4pm
RLE Conference Center: Hermann Anton Haus and Jonathan Allen Rooms 36-428/36-462
Reception following the Lecture

 

Fall 2014

October 29: John Klamkin

Boston University
Integrated Photonics: From On-Chip Interconnects to Mars Communications

Photonic integrated circuits (PICs) have evolved over a period of more than 30 years from one-off devices that were realized with complex crystal growth steps to now foundry qualified circuits that yield high performance and wafer uniformity. This evolution was fostered by the maturation of compound semiconductor materials as well as the exploitation of already matured silicon manufacturing processes that were developed for the microelectronics industry. A field that was once dominated by indium phosphide now showcases a host of other photonic materials including silicon, silica, lithium niobate, polymers, as well as hybrid platforms integrating more than one of these materials. PICs reduce size, weight and power, and increase performance and reliability. The range of applications impacted by this technology include transceivers for telecommunications, optical interconnects for data centers and high-performance computers, microwave photonics for phased-array radars and radio astronomy, readout circuits for fiber temperature and strain sensors, and transmitters for deep space communications. This talk will describe several examples of high-performance PICs and novel materials for nanophotonic integrated circuits.

11am
Haus Room, 36-428

 

November 19: Edo Waks

University of Maryland
Coherent control of light-matter interactions in photonic crystals

Two dimensional photonic crystals coupled to quantum dots are a highly promising device platform for compact integrated quantum photonic devices. Quantum dots implement a stable qubit system in a solid. When coupled to photonic crystals, a quantum dot can strongly interact with a single photon due to very strong light-matter interactions. This device platform enables efficient atom-photon interfaces on-a-semiconductor chip. In this talk, I will discuss our work on coupling indium arsenide (InAs) QDs to photonic crystal structures in order to strong interfaces between atomic and photonic qubits for quantum networking and photonic quantum computation. I will discuss our work on developing a quantum transistor, where the spin of a quantum dot conditionally switches the quantum state of a photon [1]. This transistor forms the fundamental building block for quantum networks and photonic quantum computation. I will also discuss our recent experimental realization of all-optical coherent control of vacuum Rabi oscillations [2]. Such control can enable controlled synthesis of non-classical light on a chip, a key requirement for quantum sensing.
[1] Kim, H., Bose, R., Shen, T. C., Solomon, G. S. & Waks, E. A quantum logic gate between a solid-state quantum bit and a photon. Nat Photon 7, 373-377, Available from:
http://dx.doi.org10.1038/nphoton.2013.48 (2013).
[2] Bose, R., Cai, T., Choudhury, K. R., Solomon, G. S. & Waks, E. All-optical coherent control of vacuum Rabi oscillations. Nat Photon advance online publication, Available from: http://dx.doi.org/10.1038/nphoton.2014.224 (2014).

11am
Haus Room, 36-428

 

December 3: Stephan Reitzenstein

Institute of Solid State Physics, Technische Universität Berlin
Quantum optics with semiconductor nanostructures – Towards deterministic sources for quantum communication networks

The emerging field of quantum optics in semiconductor nanostructures has benefited enormously from the excellent optical properties of self-assembled quantum dots (QDs). Acting as high quality photon emitters, they have paved the way for single photon sources, and sources of entangled photon pairs [1]. Recently, they allowed for the observation of spin- photon entanglement and quantum teleportation which are key results for future quantum communication networks. In this talk, I will report on our recent developments in the deterministic fabrication of single QD quantum devices and on the realization of coupled cQED systems. In particular, an in-situ electron beam lithography approach will be presented which allows us to precisely pattern photononic nanostructures which are aligned to preregistered QDs in order to boost their photon extraction efficiency in deterministic quantum light sources [2, 3]. Beyond the realization of single nanophotonics structures I will also present a novel scheme for fully integrated on-chip quantum optics. Here, we use for the first time an integrated electrically driven QD-microlaser to resonantly excite a coupled QD-microcavity system operating in the weak coupling regime [4]. This concept can pave the way for compact integrated sources of single photons and entangled photon pairs.
[1] A. Shields, Nat. Photonics 1, 215 – 223 (2007)
[2] M. Gschrey et al., Appl. Phys. Lett. 102, 251113 (2013)
[3] M. Gschrey et al., arXiv:1312.6298 (2013)
[4] E. Stock et al., Adv. Mat. 25, 707 (2013)

11am
Allen Room, 36-462

 

December 17: Eric Zhu

University of Toronto
High-Purity Entangled Photon Pairs from a Poled Optical Fiber: Characterization and Application

In this talk, I will discuss our group’s work with a novel source of broadband telecom-band polarization-entangled photon pairs, the periodically-poled silica fiber (PPSF). While other fiber-based sources must exploit the process of spontaneous four-wave-mixing due to the lack of a non-zero second-order optical nonlinearity, PPSF exhibits both a second-order nonlinearity and a weak birefringence. The presence of a type-II quasi-phase-matched parametric downconversion process in the fiber allows us to directly generate high-quality polarization-entangled photon pairs. Our recent progress includes a ten-fold improvement in the downconversion efficiency, and exploiting the broadband nature of the entangled photon pairs to perform multi-user quantum key distribution.

11am
56-114

 

Spring 2014

February 26: Jacob M. Taylor

JQI/NIST & University of Maryland
Light and matter: towards macroscopic quantum systems

Advances in quantum engineering and material science are enabling new approaches for building systems that behave quantum mechanically on long time scales and large length scales. I will discuss how microwave and optical technologies are leading the way toward new domains of many-body systems, both classical and quantum, using photons and phonons as the constituent particles. Furthermore, I will highlight practical consequences of these advances, including improved force and acceleration sensing, efficient signal transduction, and topologically robust photonic circuits. Finally, I will consider how these developing technologies can enable a new approaches for quantum computing and quantum simulation using nonlinear optical devices.

2pm
Haus Room, 36-428

 

March 5: Alexander V. Sergienko

Boston University
Effective Imaging Using High-Order Symmetry of Correlated Orbital Angular Momentum (OAM) States

We discuss a new approach that allows object identification using fewer resources than in conventional pixel-by-pixel imaging based on exploiting the enhanced sensitivity of high-order correlated orbital angular momentum states to multiple azimuthal Fourier coefficients [1]. A major contribution of Wigner’s work was the introduction of group theory to study both the dynamics and the classification of states in quantum mechanics. The use of rotational symmetry to study the properties of angular momentum eigenstates is particularly associated with him. Following along a similar but complementary path, we have shown that advances in the study of entangled two-photon states allow the rapid detection of rotational symmetries in complex macroscopic objects. The knowledge of this high-order symmetry structures can allow identification, and in some circumstances reconstruction, of the object much more efficiently than in current image recognition applications. This suggests some possible future applications.
[1] Nestor Uribe-Patarroyo, A. Fraine, D. S. Simon, O. Minaeva, A. V. Sergienko, Phys. Rev. Lett. 110, 043601 (2013).

2pm
Haus Room, 36-428

 

March 19: Wolfgang Tittel

University of Calgary
Measurement-device-independent QKD across the Calgary network: enhanced security and a step towards the quantum repeater

Abstract unavailable

2pm
Grier Room A, 34-401A

 

April 2: John C. Howell

University of Rochester
Compressive Quantum Sensing

Compressive sensing utilizes sparsity to realize efficient image reconstruction. It is a valuable processing technique when cost, power, technology or computational overhead are limited or high. In the quantum domain technology usually limits efficient acquisition of weak or fragile signals. I will discuss the basics of information theory, compression, and compressive sensing. I will then discuss our recent work in compressive sensing. The topics of discussion include low-flux laser Radar, photonic phase transitions, high resolution biphoton ghost imaging, Ghost object tracking, 3D object tracking and high dimensional entanglement characterization. I will touch lightly on our current work of rapid wavefunction reconstruction and wavefront sensing. As an example, we were able to efficiently and rapidly reconstruct high dimensional joint probability functions of biphotons in momentum and position. With conventional raster scanning this process would take approximately a year, but using double-pixel compressive sensing, the pictures were acquired in a few hours with modest flux.

2pm
Haus Room, 36-428

 

April 9: Alán Aspuru-Guzik

Harvard University
Quantum simulation for chemistry: Algorithms and early quantum experiments

One of the most promising applications of quantum computers and controllable quantum devices is the simulation of physical systems of interest. This is, after all, the main early motivation of Richard Feynman for the construction of quantum computers. About thirty percent of the computer time of current Department of Energy supercomputers is spent simulating molecules, proteins and materials. Can quantum computers provide efficient exact solutions for these problems? Over the last few years, My group and I have been working on developing quantum algorithms for the simulation of molecular electronic structure, quantum dynamics and classical problems such as protein folding. I will overview the algorithms developed to date and their relationships and will highlight a few of the experimental implementations that we have carried out with collaborators around the world on early-prototype quantum devices. I will devote specific attention to our recently-proposed quantum variational eigensolver, which can be employed to simulate systems on almost any current quantum device.

2pm
Grier Room A, 34-401A

 

April 16: Michael R. Watts

MIT
Large-Scale Microphotonic Circuits

The development of large-scale integrated (LSI) circuits in the 1970s led to a revolution in microelectronics with the development of the microprocessor that revolutionized the world of computing and computer science, ultimately resulting in the Internet-based world we live in today. Recent developments in microphotonics point to a similar revolution taking place today in the development of large-scale integrated photonic (LSI-P) circuits. Microphotonic circuits can dramatically alleviate communication bottlenecks, reduce power consumption, enable high-frequency high-fidelity filtering, new sensor modalities, precision timing, and the direct generation of high-frequency electromagnetic fields in chip-scale CMOS -compatible solutions. Already, breakthroughs in microphotonic circuits have led to the ability to freely manipulate polarization states on-chip enabling the first demonstration of a polarization independent microphotonic circuit, the ability to detect infrared radiation approaching fundamental noise limits, transmit optical data with a one-hundred-fold reduction in power consumption relative to electrical communications, and route optical data at nanosecond switching speeds on a silicon chip for the first time. In this talk, we present on recent developments in microphotonic devices and circuits, including a one-femtojoule-per-bit silicon modulator, nanophotonic phased arrays that not only enable arbitrary pattern formation, but represent the first large-scale integrated photonic (LSI-P) circuit, and on-chip silicon lasers, all integrated within the world’s first 300mm silicon photonics platform.

2pm
Grier Room A, 36-401A

 

Cancelled April 23: Carlos Meriles

City College of New York
The Nitrogen-Vacancy center in diamond as a nanoscale spin sensor

 

April 30, THE HERMANN ANTON HAUS LECTURE: David A.B. Miller

Stanford University
How to design any optical component… and how to avoid it

4pm
RLE Conference Center: Hermann Anton Haus and Jonathan Allen Rooms 36-428/36-462
Reception following the Lecture