Seminars are Wednesdays, 11:00AM–12 NOON
Haus Room, 36-428 (*unless otherwise noted)
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Winter 2021

January 27th: Dr. Amir Ghadimi

Swiss Center for Electronics and Micro/nano technology (CSEM)
Electro-optic and nonlinear photonic integrated circuit (PIC) platform based on lithium niobate on insulator (LNOI)

Abstract: Lithium niobate on insulator (LNOI) is one of the most promising emerging platforms for photonics integrated circuits (PICs) that comprises a unique set of interesting optical properties such as: a high electro-optic (EO) coefficient, high intrinsic 2nd and 3rd order nonlinearities, and a large transparency window (350 nm – 5500nm). Lithium niobate (LiN) has attracted a lot of attention since the 1970s, however, most of its industrial success has been limited to devices made from bulk LiN crystals in the form of free-space or fiber-coupled components using ion-implanted waveguides. Recent advancements in bonding of single crystal thin films of LiN onto silicon substrates (LNOI), opens a new avenue to explore the advantages of LiN in the context of PICs and to benefit from their miniaturization, cost reduction, scalable manufacturing and integration. In the LNIO platform, waveguides are fabricated using reactive ion etching (RIE) in a LiN thin film which allows for significantly higher refractive index contrast () compared to traditional waveguides made by ion implantation technology in bulk crystals (). This allows to reduce the optical mode volume by more than ~100x. Such high confinement not only results in more efficient and faster modulators but also in significantly smaller bending radii and PIC footprints, which, ultimately enables designing complex PICs with tens of components in a millimeters-size chips. In an LNOI platform we can combine high performance active EO components such as modulators, phase shifters and tunable cavities with unique optical nonlinearities at a wide range of wavelengths to achieve truly novel functionalities and PIC designs that are beyond the capabilities of any PIC platform commercially available today. In this talk I will present the recent progress at CSEM toward developing an EO and nonlinear PIC platform based on LNOI. We start by reviewing the advantages of LNOI platform for various application areas such as telecom, optical signal processing, programmable PICs, LiDAR, spectroscopy, quantum information processing, and nonlinear photonic. Then we will review how LNOI platform fits within the industrial PIC ecosystem and how it compares with other PIC platforms such as Si, SiN and InP. We then discuss the challenges in fabricating high quality photonics circuits in LNOI and will review CSEM’s recent results in design, fabrication, and testing of high quality LNOI photonic circuits. Next, we briefly review few successful example and experiments performed by CSEM or in collaboration with other groups in the areas of nonlinear photonics and quantum information processing. Finally, I will present the future perspectives of our LNOI platform including the process design kit (PDK) library and the means that interested parties can access our platform as a pre-commercial foundry service.

Bio: Dr. Amir H. Ghadimi is currently a senior scientist and a group leader at the Swiss Center for Electronics and Micro/nano technology (CSEM). He is currently leading the efforts at CSEM in the areas of PICs and PIC based sensing where together with his team they are developing two PIC platforms based on SiN and LNOI. He obtained his PhD. in electrical engineering in 2018 from the Swiss Federal Institute of Technology (EPFL). His PhD research focused on quantum optomechanics, precision sensing and applications of high Q optical and mechanical resonators. He is the recipient of Swiss national funding (SNF) Bridge discovery grant (2020), Swiss Physical Society (SPS) 2019 young scientist award, Swiss Nanotechnology best PhD award (2018) and European frequency and time forum (EFTF) best paper award (2018).

Via Zoom (

January 20th POSTPONED: Professor Jens Eisert

Berlin Free University – Institut für Theoretische Physik
Semi-device-independent benchmarking, certification, and tomography

Abstract: At the same time as the development of quantum technologies progresses rapidly, new demands concerning the certification of their operation emerge. A question relevant for the application of various quantum technologies consequently is how the user can ensure the correct functioning of the quantum devices [1]. In a number of instances, specifically in quantum simulation and quantum computing, challenges in appropriately benchmarking components or entire protocols constitute a widely acknowledged bottleneck. This talk will suggest several new takes to the problem at hand: We will see how data from SPAM-robust randomized benchmarking [2] can be used to perform process tomography of quantum gates in an experimentally-friendly and provably sample optimal fashion [3], making use of a machinery of compressed sensing and exploiting structure – that is to say, the components of a quantum circuit. We will see how quantum states can be characterizes provably even with imperfect detectors in what could be called semi-device-dependent tomography [4]. The issue becomes more challenging when one aims at certifying the functioning of an entire device. We will look at limitations to black-box verification for sampling problems that show a quantum advantage or “supremacy” [5], will have a fresh look at Hamiltonian learning [6] and will see that in some instances [7], one can ironically certify the correctness of a device even if one cannot efficiently predict its performance.

[1] Quantum certification and benchmarking, J. Eisert, D. Hangleiter, N. Walk, I. Roth, D. Markham, R. Parekh, U. Chabaud, E. Kashefi, Nature Reviews Physics 2, 382-390 (2020).
[2] Randomized benchmarking for individual quantum gates, E. Onorati, A. H. Werner, J. Eisert, Phys. Rev. Lett. 123, 060501 (2019).
[3] Recovering quantum gates from few average gate fidelities, I. Roth, R. Kueng, S. Kimmel, Y.-K. Liu, D. Gross, J. Eisert, M. Kliesch, Phys. Rev. Lett. 121, 170502 (2018).
[4] Semi-device-dependent blind quantum tomography, I. Roth, J. Wilkens, D. Hangleiter, J. Eisert, arXiv:2006.03069 (2020).
[5] Sample complexity of device-independently certified quantum supremacy, D. Hangleiter, M. Kliesch, J. Eisert, C. Gogolin, Phys. Rev. Lett. 122, 210502 (2019).
[6] In preparation (2020).
[7] J. Haferkamp, D. Hangleiter, A. Bouland, B. Fefferman, J. Eisert, and J. Bermejo-Vega, arXiv:1908.08069, Phys. Rev. Lett. (2020).

Bio: He is known for his research in and has made numerous contributions to quantum information science and quantum many-body theory in condensed matter physics. He has made significant contributions on entanglement theory and the study of quantum computational models, as well as quantum optical implementations of protocols in the quantum technologies and the study of complex quantum systems. He is also notable as one of the co-pioneers of quantum game theory with Maciej Lewenstein and PhD advisor Martin Wilkens.

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January 13th: Dr. Kin Chung Fong

Raytheon BBN Technologies
Graphene-based single-photon detector for quantum information science and astrophysics

Abstract: High sensitivity photon detectors are essential in qubit measurement and remote entanglement, as well as dark matter detection and observing the cosmic infrared background in astrophysics. However, sensing in microwave and far-infrared spectrum is challenging because of the low photon energy. In this talk, we will present how to leverage the giant thermal response of graphene electrons for photon detection. Interestingly, when our graphene bolometer achieves a record-high sensitivity of 10-19 W/Hz1/2, this sensitivity is limited, no longer by extrinsic factors but, by the statistical thermal fluctuation intrinsic to the graphene electrons as a canonical ensemble at 0.2 K [1]. Using the graphene-based Josephson junction, we demonstrate the single-photon detection in the infrared regime by observing the photon shot noise [2]. As an outlook, we will discuss how the unique properties of two-dimensional materials will open new opportunities in quantum information science.

[1] Nature 586, 42 (2020) [2] arXiv:2011.02624.

Bio: Born and raised in Hong Kong, Dr. Kin Chung Fong came to the United States to pursue his PhD under the supervision of Prof. Chris Hammel at Ohio State University. This is where KC develops his passion on high sensitivity experiments to observe new physical phenomena that cannot be otherwise measured. These include detecting a single electron spin magnetic resonance for nanoscale MRI, measuring superconducting qubits with quantum-limit amplifications, and detecting Dirac fluid in graphene. After his postdoc at Caltech, KC joined BBN Technologies in 2013. His research now focuses on studying the fundamental physics of strongly interacting Dirac and Weyl fermions in condensed matter systems with their connections to holographic principle, and developing the Josephson junction single photon detector for quantum information science, radioastronomy, and the search of dark matter axions. KC loves spending time outdoor with his family during weekends and learning new things from friends and collaborators, especially over a coffee!

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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.

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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.

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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.

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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 (, 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.

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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.

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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.

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Summer 2020

September 23rd: Professor Christophe Galland

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.

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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.

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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.

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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.

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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.

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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.

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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.

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

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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.

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.

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.

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

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.

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.

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 ( 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.

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 ( at the University of Utah. He received S.M. and Ph.D. degrees from MIT.

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.

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.


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.

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.

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.

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.

Haus Room, 36-428


Image credit: Greg Steinbrecher