Seminars are Wednesdays, 11:00AM–12 NOON
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Seminar calendar:

 

Summer 2021

July 14th: Valeria Saggio

University of Vienna (Austria)
Quantum speed-ups in reinforcement learning

Abstract: The field of artificial intelligence (AI) has experienced major developments over the last decade. Within AI, of particular interest is the paradigm of reinforcement learning (RL), where autonomous agents learn to accomplish a given task via feedback exchange with the world they are placed in, called an environment. Thanks to impressive advances in quantum technologies, the idea of using quantum physics to boost the performance of RL agents has been recently drawing the attention of many scientists. In my talk I will focus on the bridge between RL and quantum mechanics, and show how RL has proven amenable to quantum enhancements. I will provide an overview of the most recent results — for example, the development of agents deciding faster on their next move [1] — and I will then focus on how the learning time of an agent can be reduced using quantum physics. I will show that such a reduction can be achieved and quantified only if the agent and the environment can also interact quantum-mechanically, that is, if they can communicate via a quantum channel [2]. This idea has been implemented on a quantum platform that makes use of single photons as information carriers. The achieved speed-up in the agent’s learning time, compared to the fully classical picture, confirms the potential of quantum technologies for future RL applications. [1] Sriarunothai, T. et al. Quantum Science and Technology 4, 015014 (2018). [2] Saggio, V. et al. Nature 591, 229–233 (2021).

Bio: Valeria Saggio is currently a post-doctoral researcher at the University of Vienna (Austria), where she obtained her Ph.D. under the supervision of Prof. Philip Walther. She carried out her Master thesis at the University of Florence (Italy) and did an internship at the Queen’s University Belfast (UK) during her studies at the University of Catania (Italy), where she obtained her B.A. and M.S. in Physics. Her research has a strong experimental focus on quantum computing with photonic platforms. During her Ph.D. she worked on demonstrating efficient detection of multipartite entanglement in photonic cluster states, as well as on applications of quantum mechanics to reinforcement learning. Her research interests include working with bulk as well as integrated optics.

11am
Via Zoom (https://mit.zoom.us/j/94435855934)

June 16th: Mitsumasa Nakajima

NTT Device Technology Labs
Scalable reservoir computing on coherent linear photonic processor

Abstract: Recently, photonic implementation of artificial neural networks (ANNs) has catching interests because they have a great potential to reduce the operational power and latency beyond the electronic computing. The photonic circuit can solve large scale matrix operation, which is a dominant factor of ANN computation, with ultrafast propagation speed thanks to their inherent parallelism in space, frequency and time division. Here, I demonstrate a reservoir computing — a randomly connected recurrent neural network — specified on-chip photonic circuit capable of operating at sub-Peta-scale Multiply-Accumulate per second speeds [1]. I also explain the relationship between deep neural network and wave equation in the waveguide, which enables large-scale integration of photonic neuromorphic circuit in future [2]. [1] M. Nakajima et al., Commun. Phys. 4, 20 (2021). [2] M. Nakajima et al., arXiv:2006.13541

Bio: Mitsumasa Nakajima received the M.E. and Ph.D. degrees in material science from the Tokyo Institute of Technology, Tokyo, Japan, in 2010 and 2015, respectively. In 2010, he joined Nippon Telegraph and Telephone (NTT) Laboratories, where he was involved in the development of large-scale optical switches. Recent his research interests are optical switches and their applications including neuromorphic photonics and optical signal processing for telecom. He was a recipient of the 8 research award including Young Engineer Award from the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan.

11am
Via Zoom (https://mit.zoom.us/j/95412795757)

Spring 2021

May 19th: Prof. Alex Gaeta

Columbia University
Nonlinear photonics for quantum applications

Abstract: Nonlinear integrated photonics is is on the cusp of realizing devices that will be widely used for applications in data communications, sensing, time-frequency metrology, and quantum information science. I will describe our recent work on developing nonlinear optical processes that can be used for generating squeezed states of light, quantum random number generation, and quantum frequency conversion.

Bio: Gaeta received his Ph.D. in 1991 in Optics from the University of Rochester. He joined the faculty in the Department of Applied Physics and Applied Mathematics at Columbia University in 2015, where he is the David M. Rickey Professor. Prior to this, he was a professor in the School of Applied and Engineering Physics at Cornell University for 23 years. He has published more than 250 papers in quantum and nonlinear optics. He co-founded PicoLuz, Inc. and was the founding Editor-in-Chief of Optica. He is a Fellow of the OSA, APS, and IEEE, is a Thomson Reuters Highly Cited Researcher, and was awarded the 2019 Charles H. Townes Medal from the OSA.

11am
Via Zoom (https://mit.zoom.us/j/99461352689)

May 5th: Prof. Hong Tang

Yale University
Cavity electro-optics for microwave-to-optics conversion in the quantum ground state

Abstract: Microwave-to-optical quantum converters represent an indispensable component for quantum communication in future quantum networks. To maintain quantum coherence, it is critical for such devices to operate at milli-Kelvin temperatures in the quantum ground state. Integrating photonics with superconductors at milli-Kelvin temperatures is particularly challenging since the optical excitation leads to unavoidable heating and excess microwave noise, thus placing the device systems in a thermal state as opposed to the desired ground state. In this work, we demonstrate efficient bidirectional microwave-to-optical conversion with an electro-optic device fabricated on an integrated AlN photonic platform in a milli-Kelvin environment. Our device operates near its quantum ground state and meanwhile offers 0.12% conversion efficiency – a rate that is suitable for building two-node quantum network through heralding protocols.[1] This fully integrated converter offers advantages including tunability, scalability, and high pump power handling capability. Harnessing a pulsed drive scheme, we suppress the microwave resonator’s thermal occupancy by 30 dB to as low as 0.09±0.06 quanta (92±5% ground state probability). By studying microwave noise thermodynamics, we unravel the underlying light-induced noise generation mechanisms, which provide important guidelines for future deployment of chipscale electro-optical devices as quantum links between superconducting quantum computers. [2,3] References [1] C. Zhong, Z. Wang, C. Zou, M. Zhang, X. Han, W. Fu, M. Xu, S. Shankar, M. H. Devoret, and H. X. Tang, Proposal for Heralded Generation and Detection of Entangled Microwave–Optical-Photon Pairs, Phys. Rev. Lett. 124, 10511 (2020). [2] W. Fu, M. Xu, X. Liu, C. L. Zou, C. Zhong, and X. Han, Ground-State Pulsed Cavity Electro-Optics for Microwave-to-Optical Conversion, ArXiv Preprint ArXiv (2020). [3] M. Xu, X. Han, C.-L. Zou, W. Fu, Y. Xu, C. Zhong, L. Jiang, and H. X. Tang, Radiative Cooling of a Superconducting Resonator, Phys. Rev. Lett. 124, 33602 (2020).

Bio: Hong Tang is the Llewellyn West Jones, Jr. Professor of Electrical Engineering, Physics and Applied Physics at Yale University. His research utilizes integrated photonic circuits to study photon-photon, photon-phonon and photon-spin interactions as well as quantum photonics involving microwave and optical photons. He has been on Yale faculty since 2006. He is a recipient of the NSF CAREER Award and Packard Fellowship in Science and Engineering.

11am
Via Zoom (https://mit.zoom.us/j/94441686370)

April 7th: Dr. Chris Anderson

University of Chicago
Spin qubits in silicon carbide for quantum technologies

Abstract: Defect spin qubits in silicon carbide (SiC) with associated nuclear spin quantum memories can leverage near-telecom emission and wafer-scale semiconductor device engineering for creating quantum technologies. Here, I highlight recent advances with the neutral divacancy defect (VV0) in SiC within the context of long-distance quantum communication and repeater schemes. Broadly, I will illustrate how quantum states can be controlled, tuned, and enhanced through their integration into SiC mechanical, photonic, and electrical devices. I will first describe the isolation of single VV0 defects in functional SiC optoelectronic devices, which allows for deterministic charge state control and terahertz tuning, but also surprisingly eliminates spectral diffusion in the optical structure of these defects. I will then discuss the entanglement and control of nuclear spin registers, and show how isotopic engineering can enhance both nuclear quantum memories and electron spin coherence times, while also demonstrating high fidelity control (99.98%), initialization, and readout. Briefly, I will further highlight recent results that universally protect spin coherence from electrical, magnetic, and thermal noise, resulting in T2*>20 ms in a naturally abundant crystal. This suite of results establishes SiC as a promising platform for scalable quantum science with optically-active spins.

Bio: Chris is currently a postdoctoral scholar in the research group of David Awschalom at the University of Chicago at the Pritzker School of Molecular Engineering. Recently, he completed his PhD in Physics in the same group. Generally, Chris works on developing the physics and devices that will enable the next generation of quantum technologies using spins in semiconductors. He was awarded a NDSEG fellowship for his graduate work. Chris was a researcher in spintronics in Vanessa Sih’s group, and worked on ultrafast chemical physics in Roseanne Sension’s group at the University of Michigan, where he received a B.S in Chemistry and Physics. Chris has also worked on attosecond laser systems at the Max-Planck Institute for Nuclear Physics, and spent his early years as a molecular biology and genomics researcher.

11am
Via Zoom (https://mit.zoom.us/j/98878231527)

March 24th: Prof. Jose Capmany

Universitat Politecnica de Valencia
Field Programmable Photonic Gate Arrays: principles and applications

Abstract: Programmable Integrated Photonics (PIP) is a new paradigm in integrated optics which seeks to provide versatile and flexible circuits, systems and subsystems adaptable to a myriad of applications. In a way PIP follows a similar itinerary as that of integrated electronics 4 decades ago but with substantial differences. In this talk, after a brief introduction to PIP, I will focus on the Field Programmable Photonic Gate Array (FPPGA) device, where a common hardware becomes multifunctional by suitable software programming. I will discuss the different hardware and software tiers involved in its development and will also provide experimental results obtained both within our research group as well as in our spinoff company. Finally, I will develop some application cases (including RF-Photonics) for the device and discuss possible future evolution paths.

Bio: José capmany is professor of Photonics at the Universitat politècnica de València, Spain and leader of the Photonics Rsearch Labs (www.prl.upv.es). He holds a MSc+BSc+PhD in Telecommunications Engineering and a MSc+BSc+PhD in Physics. His research stands out in two fields: Microwave Photonics and more recently the programmable integrated photonics. He has published over 640 papers in international JCR journals and conferences in different field of optical communications and photonic processing. He received the Premio Nacional de Investigación (National Research Award) Leonardo Torres Quevedo in Engineering in 2020 and the Premio Rey Jaime I in New Technologies (2012) for his contribution to the fields of Microwave and Programmable Photonics. In 2016 he obtained an Advanced Grant from the European Research Council (ERC) to develop the field of Programmable Integrated Photonics and in 2019 a Proof of Concept Grant from the same institution. He is a Fellow of the Institute of Electrical and Electronics Engineers (IEEE), the Optical Society of America (OSA) and the Institution of Engineering Technology (IET). He has co-founded 2 spinoff companies: VLC Photonics (www.vlcphotonics.com), (specific purpose photonic circuit design house recently acquired by Hitachi High Technologies), and iPronics, Programmable Photonics (www.ipronics.com), (programmable optical chips), selected by Nature magazine as one of the 44 companies to watch within the SpinoffPrize 2020 call.

11am
Via Zoom (https://mit.zoom.us/j/93434717660)

March 17th: Dr. Denis Sukachev

University of Calgary
Interfaces between color centers and photons

Abstract: Quantum networks enable a broad range of practical and fundamental applications spanning distributed quantum computing through sensing and metrology. A key element of such networks is an interface between photons and stationary quantum memories–qubits. I will first present the recent results on coupling the Silicon-Vacancy color centers in diamond to photons via nanophotonic cavities. Next, I will introduce a novel approach based on nano-optomechanics which we use to control electron spins of the Nitrogen-Vacancy centers in diamond with telecom photons at room temperature. The latter method does not involve qubit optical transitions and is insensitive to spectral diffusion. This approach can be applied to a broad range of solid-state qubits and paves the way to hybrid quantum networks.

Bio: I received the undergraduate degree in Physics and Mathematics from the Moscow Institute of Physics and Technology and then in 2013 earned PhD in Physics from Lebedev Physical Institute for laser cooling and trapping of thulium atoms. In 2014, I moved to Massachusetts to work as a postdoc in Misha Lukin’s group at Harvard University. Our sub-team was focused on study of the silicon-vacancy defects in diamond — a new promising color center for quantum networking. In 2019, I joined Paul Barclay’s lab at the University of Calgary as a staff scientist to develop a new spin-photon interface based on cavity optomechanics.

11am
Via Zoom (https://mit.zoom.us/j/96071924168)

March 10th: Florian Marquardt

Max Planck Institute for the Science of Light
Self-learning Machines based on Hamiltonian Echo Backpropagation

Abstract: Physical learning machines use physical dynamics to achieve the same kind of general information processing and training that artificial neural networks are known for, but possibly faster and more energy-efficient. Self-learning machines can be defined as an ambitious subset of physical learning machines: They can be trained without requiring any form of external feedback to update the trainable parameters inside the device. In this talk, I will describe a new general idea that can be used to realize self-learning starting from any kind of Hamiltonian system with time-reversible dynamics. I will explain the reasoning and intuitive ideas behind it, as well as the ingredients that will be useful in building such devices in various physical platforms.

Bio: Since 2016, Florian Marquardt leads the theory division of the Max Planck Institute for the Science of Light in Erlangen, Germany. His work covers the intersection of nanophysics and quantum optics. Research topics include cavity optomechanics, topological transport, quantum many-body dynamics, and the interface between machine learning and physics. After defending his thesis in 2002 in Basel, Switzerland, he was a postdoctoral fellow at Yale before becoming a junior research group leader at the Ludwig-Maximilians-Universität Munich and finally a full professor and subsequently Max Planck director at Erlangen.

11am
Via Zoom (https://mit.zoom.us/j/97593235563)

March 3rd: Prof. 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.

11am
Via Zoom (https://mit.zoom.us/j/97518824305)

February 26th: Sri Krishna Vadlamani

UC Berkeley
Spectral Broadening in Tunnel Transistors and Physics-Based Machines for Discrete Optimization

Abstract: I shall talk about the two different projects in the field of energy-efficient computation that I worked on in my PhD:

Part 1 (Device Physics): Tunnel Field-Effect Transistors (tFETs) are one of the candidate devices being studied as energy-efficient alternatives to the present-day MOSFETs. In these devices, the preferred switching mechanism is the alignment (ON) or misalignment (OFF) of two energy levels or band edges. Unfortunately, energy levels are never perfectly sharp. When a quantum dot interacts with a wire, its energy level is broadened. Its actual spectral shape controls the current/voltage response of such transistor switches, from on (aligned) to off (misaligned). The most common model of spectral line shape is the Lorentzian, which falls off as reciprocal energy offset squared. Unfortunately, this is too slow a turnoff, algebraically, to be useful as a transistor switch. Electronic switches generally demand an ON/OFF ratio of at least a million. Steep exponentially falling spectral tails would be needed for rapid off-state switching. This requires a new electronic feature, not previously recognized: narrowband, heavy-effective mass, quantum wire electrical contacts, to the tunneling quantum states.

Part 2 (Systems Physics): Optimization is built into the fundamentals of physics. For example, physics has the principle of least action, the principle of minimum power dissipation, also called minimum entropy generation, and the adiabatic principle, which, in its quantum form, is called quantum annealing. Machines built on these principles can solve the mathematical problem of optimization, even when constraints are included. Further, these machines become digital in the same sense that a flip–flop is digital when binary constraints are included. A wide variety of machines have had recent success at optimizing the Ising magnetic energy. We demonstrate that almost all those machines perform optimization according to the principle of minimum power dissipation as put forth by Onsager. Moreover, we show that this optimization is equivalent to Lagrange multiplier optimization for constrained problems.

Bio: Sri Krishna Vadlamani (Sri) is a fifth-year PhD student in Prof. Eli Yablonovitch’s group in the EECS Dept. at UC Berkeley. He is interested in physics-based computation, both classical and quantum, with a particular interest in the potential impact of physics ideas on Machine Learning theory and applications. He received his undergraduate degree in Electrical Engineering from IIT Bombay, India, in 2016.

12pm
Via Zoom (https://mit.zoom.us/j/92408916520)

February 24th: Prof. Brian Gerardot

Heriot-Watt University
Quantum Light and Strongly Correlated Electronic States in a Moiré Heterostructure

Abstract: SThe unique physical properties of two-dimensional materials, combined with the ability to stack unlimited combinations of atomic layers with arbitrary crystal angle, has unlocked a new paradigm in designer quantum materials. For example, when two different monolayers are brought into contact to form a heterobilayer, the electronic interaction between the two layers results in a spatially periodic potential-energy landscape: the moiré superlattice. The moiré superlattice can create flat bands and quench the kinetic energy of electrons, giving rise to strongly correlated electron systems. Further, single particle wave packets can be trapped in the moiré potential pockets with three-fold symmetry to form ‘quantum dots’ which can emit single photons. Here I will present magneto-optical spectroscopy of a 2H-MoSe2/WSe2 heterobilayer device with ~3° twist. I will discuss moiré-trapped inter-layer excitons, which can emit quantum light, and intra-layer excitons, which exhibit a large number of strongly correlated electron and hole states as a function of fractional filling.

Bio: Professor Brian Gerardot holds a Chair in Emerging Technology from the Royal Academy of Engineering and leads the Quantum Photonics Lab at Heriot-Watt University in Edinburgh, Scotland (more information: http://qpl.eps.hw.ac.uk/). His research, at the interface of quantum optics, condensed-matter physics, and materials science, aims to engineer and controllably manipulate quantum states in semiconductor devices, in particular with III-V quantum dots and van der Waals heterostructure devices. Brian obtained a BS from Purdue University and a PhD in Materials Science from UC Santa Barbara.

11am
Via Zoom (https://mit.zoom.us/j/96268350649)

Winter 2021

February 17th: Eric I. Rosenthal

JILA
Efficient and low-backaction quantum measurement using a chip-scale detector

Abstract: Superconducting qubits are a leading platform for scalable quantum computing and quantum error correction. One feature of this platform is the ability to perform projective measurements orders of magnitude more quickly than qubit decoherence times. Such measurements are enabled by the use of quantum-limited parametric amplifiers in conjunction with ferrite circulators – magnetic devices which provide isolation from noise and decoherence due to amplifier backaction. Because these non-reciprocal elements have limited performance and are not easily integrated on-chip, it has been a longstanding goal to replace them with a scalable alternative. Here, we demonstrate a solution to this problem by using a superconducting switch to control the coupling between a qubit and amplifier. Doing so, we measure a transmon qubit using a single, chip-scale device to provide both parametric amplification and isolation from the bulk of amplifier backaction. This measurement is also fast, high fidelity, and has 70% efficiency, comparable to the best that has been reported in any superconducting qubit measurement. As such, this work constitutes a high-quality platform for the scalable measurement of superconducting qubits.

Bio: Eric I. Rosenthal is a Ph.D. student at the University of Colorado, Boulder, under the advisement of Professor Konrad Lehnert at JILA. He received his B.A. and M.S. in physics from the University of Pennsylvania in 2015 and is expected to receive his Ph.D. in physics in the spring of 2021. His research interest is in the advancement of quantum information technology using superconducting systems. In particular, his research has involved the development of superconducting switches, amplifiers, and non-reciprocal devices to improve the measurement of superconducting qubits.

11am
Via Zoom (https://mit.zoom.us/j/91675241753)

February 10th: Prof. Boubacar Kante

UC Berkeley
Topological light sources and sensors

Abstract: Topology plays a fundamental role in contemporary physics and enables new information processing schemes and wave device physics with built-in robustness. Recently, significant efforts have been devoted to transposing topological principles to bosonic systems. In the first part of this talk, I will discuss our invention of the first topological laser, a non-reciprocal light source capable of coupling stimulated emission to selected waveguide output in a controllable manner. I will also discuss unique optical devices based on this platform. In the second part of the talk, I will discuss our recently proposed scheme to systematically implement singularities known as exceptional points in passive plasmonics. I will discuss the new scheme and how we overcame current immuno-assay nano sensing record with plasmons by more than two orders of magnitude.

Bio: Boubacar Kanté is an associate professor of Electrical Engineering and Computer Sciences (EECS) at the University of California Berkeley. In 2010, he received a Ph.D degree in Engineering/Physics from “Université de Paris Sud” (Orsay-France). He was assistant professor and then associate professor of Electrical and Computer Engineering (ECE) at UC san Diego from 2013 to 2018. His research interests include wave-matter interaction and nano-optics. Boubacar Kanté is a 2020 Moore Inventor Fellow. He received the 2017 Office of Naval Research (ONR) Young Investigator Award, the 2016 National Science Foundation (NSF) Career Award, The best undergraduate teacher award from UC San Diego Jacob School of Engineering in 2017, the 2015 Hellman Fellowship, the Richelieu Prize in Sciences from the Chancellery of Paris Universities for the best Ph.D in France in Engineering, Material Science, Physics, Chemistry, Technology in 2010, the Young Scientist Award from the International Union of Radio Science (URSI) in Chicago in 2007, the Fellowship for excellence from the French Ministry of Foreign Affairs in 2003 for his undergraduate studies, a Research Fellowship from the French Research Ministry for his Ph.D studies.

11am
Via Zoom (https://mit.zoom.us/j/94195627674)

February 3rd: Dr. Martin Suchara

Argonne National Laboratory
Quantum Network Simulations – Towards Reliable, Scalable, and Secure Quantum Network Architectures

Abstract: Recent advances in quantum information science enabled the development of quantum communication network prototypes and created an opportunity to study full-stack quantum network architectures. This talk introduces SeQUeNCe, a comprehensive, customizable quantum network simulator. Our simulator consists of five modules: Hardware models, Entanglement Management protocols, Resource Management, Network Management, and Application. This modularized framework is suitable for simulation of quantum network prototypes that capture the breadth of current and future hardware technologies and protocols. We implement a comprehensive suite of network protocols and demonstrate the use of SeQUeNCe by simulating a quantum key distribution network, a teleportation network, and a metropolitan quantum network in the Chicago area consisting of nine routers equipped with quantum memories. Quantum network simulations are expected to play an increasingly important role in designing future quantum networks that scale to long distances and large number of hosts, and meet the latency, reliability and security needs of emerging applications. SeQUeNCe is freely available on GitHub.

Bio: Martin Suchara is a Computational Scientist at Argonne National Laboratory and at the University of Chicago with expertise in quantum computing and quantum communication. His group focuses on theoretical studies of photonic quantum networks, quantum error correction, quantum simulations, and optimizations of the quantum computing software stack. Dr. Suchara is the leader of the Simulation & Systems Thrust of the Q-NEXT National Quantum Information Science Research Center based at Argonne National Laboratory. Prior to joining Argonne he worked as a Principal Scientist at AT&T Labs and received postdoctoral training in quantum computing from UC Berkeley and the IBM T. J. Watson Research Center. Dr. Suchara received his PhD from the Computer Science department at Princeton University.

11am
Via Zoom (https://mit.zoom.us/j/97613945791)

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).

11am
Via Zoom (https://mit.zoom.us/j/95001956600)

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.

11am
Via Zoom (https://mit.zoom.us/j/97518824305)

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!

11am
Via Zoom (https://mit.zoom.us/j/93266078938)


Image credit: Greg Steinbrecher