May 24, 2022 10:30 AM
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May 25, 2022 4:30 PM
May 24, 2022 10:30 AM
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May 25, 2022 4:30 PM
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Hôtel Château Bromont
Hôtel Château Bromont
Opening Remarks
Pr Mathieu Juan, Institut quantique - Université de Sherbrooke
Clasical and quantum computations as tensor networks
Pr Stefanos Kourtis, Institut quantique - Université de Sherbrooke
Classical and quantum computations as tensor networks
Break
Event organized in collaboration with the RQMP and animated by Mrs. Chloé Freslon, founder of URelles
Falisha Karpati, Ph.D.
Think Differently Together: Strengthening research and innovation by embracing cognitive diversity
Louis-Philippe Lamoureux (Slides / Présentation)
Thierry Debuischert, Thales - France (postponed to Monday at 13:15 / reporté à lundi 13h15)
Closing remarks of the day
Opening remark of the day
Thierry Debuischert, Thales - France
Professor Tami Pereg-Barnea, McGill University
Dynamic topology - quantized conductance and Majoranas on wires
Professor Philippe St-Jean, Université de Montréal
Topological physics with light and matter: new horizons
Break
Louis Gaudreau, National Research Council Canada (Ottawa)
Entanglement distribution via coherent photon-to-spin conversion in semiconductor quantum dot circuits
Philippe Lamontagne, National Research Council Canada (Montréal)
Black-Box Impossibility in the Common Reference Quantum State Model
Olivier Gagnon-Gordillo, Québec quantique lead
Presentation of the Québec Quantum ecosystem
Institut quantique - Université de Sherbrooke
Classical and quantum computations as tensor networks
Tensor networks are multilinear-algebra data structures that are finding application in diverse fields of science, from quantum many-body physics to artificial intelligence. I will introduce tensor networks and illustrate how they can be used to represent classical and quantum computations. I will then motivate tensor network algorithms that perform or simulate computations in practice and demonstrate their performance on benchmarks of current interest, such as model counting and quantum circuit simulation. I will close with an outline of ongoing work and an outlook on future directions.
Institut quantique - Université de Sherbrooke
Optomechanics with a non-linear cavity
The possibility to operate massive mechanical oscillators close to or in the quantum regime has become central in fundamental sciences. LIGO is a prime example where quantum states of light are now used to further improve the sensitivity. Concretely, optomechanics relies on the use of photons to control the mechanical motion of a resonator, providing a path toward quantum states of massive objects and for the development of quantum sensors. In order to improve this control many approaches have been explored, some more complicated than others. In particular, in order to cool the mechanical motion a cavity can be used to realise side-band cooling. In general, linear cavities are favoured to allow for large photon number providing stronger cooling. I will show that, surprisingly, non-linear cavities can be used to achieve very efficient cooling at low powers. Indeed, even in the bad cavity limit, we have been able to cool a mechanical resonator from 4000 thermal phonons down 11 phonons. Currently limited by flux noise, this approach opens promising opportunities to achieve quantum control of massive resonators, an avenue to study foundational questions.
McGill University
Dynamic topology - quantized conductance and Majoranas on wires
This talk will address the issue of out-of-equilibrium topological systems. While many materials and devices produced in labs today are topological at equilibrium, it is desirable to have a knob to tune or induce topological properties. For example, if we could dynamically turn a superconductor into a topological superconductor we may create the sought after Majorana fermions which are potential building blocks of quantum bits.
In this context we will explore the possibility of perturbing quantum systems using time-periodic fields (i.e., radiation) and use the Floquet theory to characterize the driven states. We find that in topological systems, beyond the expected splitting of the spectrum into side bands, a change in the topology may occur. In the case of a topological superconductor, the driven system may develop new Majorana modes which do not exist at equilibrium and can be exchanged on a single wire. A protocol for exchanging Majoranas will be presented.
Université de Montréal
Topological physics with light and matter: new horizons
Topology is a branch of mathematics interested in geometric properties that are invariant under continuous deformation, e.g. the number of holes in an object. In the early 1980s it was demonstrated that similar topological properties can be defined for solids presenting appropriate symmetry elements. The discovery of these topological phases of matter has profoundly impacted our understanding of condensed matter, its influence ranging from better explaining the universality of the conductivity plateaus in the quantum Hall effect to developing new platforms for fault-tolerant quantum computation[i]. In the late 2000s, Duncan Haldane (co-laureate of the Nobel Prize in physics for the discovery of topological phases of matter) demonstrated that this topological physics is not restricted to condensed matter but can also emerge in artificial systems like photonic crystals through a careful engineering of their symmetry properties[ii]. Since then, these photonics platforms have proven to be an amazing resource for pushing the exploration of topological matter beyond what is physically reachable in the solid-state, leading to the emergence of a blooming field called topological photonics[iii].
In this presentation, I will describe recent experimental works based on exciton-polaritons, a hybrid light-matter quasiparticle, which have opened new horizons in topological photonics[iv]. The main advantages of polaritonic systems arise from their dual nature: their photonic part allows for tailoring well-defined topological properties in lattices of coupled microcavities and makes them inherently non-hermitian; on the other hand, their matter part gives rise to a strong Kerr-like nonlinearity and to lasing[v]. I will then discuss in more details a recent work in which we took profit of these assets to experimentally extract topological invariants - a fundamental quantity in topology - in a polaritonic analog of graphene[vi]. Importantly, this has allowed us to directly probe the topological phase transition occurring in a critically strained lattice - i.e. where Dirac cones have merged - a condition impossible to reach in the solid-state. I will conclude this presentation by discussing how topological protection can provide a powerful asset for generating and stabilizing many-body quantum states of light and matter. Such mesoscopic quantum objects are highly desirable as they would provide an extended playground for quantum simulation, sensing applications or for generating exotic states of light such as many-body entangled states[vii].
[i] M. Z. Hasan and C. L. Kane. Rev. Mod. Phys. 82, 3045 (2010)
[ii] F. D. M. Haldane and S. Raghu. Phys. Rev. Lett. 100, 013904 (2008)
[iii] T. Ozawa et al. Rev. Mod. Phys. 91, 015006 (2019)
[iv] D. D. Solnyshkov, G. Malpuech, P. St-Jean et al. Opt. Mat. Express 11, 1119 (2021)
[v] I. Carusotto and C. Ciuti. Rev. Mod. Phys. 85, 299 (2013)
[vi] P. St-Jean et al. Phys. Rev. Lett. 126, 127403 (2021)
[vii] P. Lodahl et al. Nature 541, 473 (2017)
Think Differently Together: Strengthening research and innovation by embracing cognitive diversity
This talk will cover:
Biography
Falisha Karpati, PhD is a neuroscientist turned inclusion consultant. Falisha’s work focuses on using neuroscience to build inclusive environments in academic, research, and scientific organizations. Her approach to inclusion centres on the interconnectedness of cognitive, demographic, and experiential diversity. Prior to starting her consultancy practice, she worked as the Training and Equity Advisor for Healthy Brains, Healthy Lives at McGill University.
Head of Applied Quantum Physics
Thales Research & Technology
Researcher
National Research Council Canada (Ottawa)
In this talk, I will present our proposed long distance entanglement distribution scheme that aims to overcome fundamental limitations present in current optical schemes. By using direct band gap semiconductor quantum dots, efficiency and heralding advantages can be exploited through photon-to-spin conversion. For this reason, materials such as GaAs are superior to Si in this type of applications. I will review current schemes to transfer polarization or time-bin encoded photonic qubits to electron spin qubits and will describe adaptations to employ heavy holes which have a number of attractive properties including g-factor tunability. Finally, I will show preliminary results on quantum dot devices using Van der Waals heterostructures which present several potential advantages such as higher confinement energies due to their atomically thin geometry, easier combination with different substrates and the possibility of encoding information in their valley degree of freedom.
Biography
Louis Gaudreau studied physics at Sherbrooke University, followed by a masters and PhD in co-supervision with Andrew Sachrajda at NRC and Alexandre Blais at Sherbrooke. During his graduate studies, Louis studied electrostatic quantum dots and realized for the first time a coupled triple quantum dot system leading to the investigation of the first exchange-only qubit. During this period he was invited to perform quantum dot experiments in Stefans Ludwig’s group at LMU in Munich. After his PhD, Louis changed fields and studied light-matter interactions by combining quantum emitters and graphene to create different hybrid systems. These experiments were done during his postdoc at ICFO in Barcelona in the nano-opto-electronics group with Frank Koppens where he was awarded the prestigious Marie-Curie fellowship. Finally, since 2015, Louis has worked as research officer at the NRC where he investigates different technologies linked to quantum information.
Researcher
National Research Council Canada (Montréal)
Black-Box Impossibility in the Common Reference Quantum State Model
We explore the cryptographic power endowed by arbitrary shared physical resources. We introduce the Common Reference Quantum State (CRQS) model, where the parties involved share a fresh entangled state at the outset of each protocol execution. This model is a natural generalization of the well-known Common Reference String (CRS) model but appears to be more powerful. In the two-party setting, a CRQS can sometimes exhibit properties associated with a Random Oracle queried once. We formalize this notion as a Weak One-Time Random Oracle (W1TRO), where we only ask of the output to have some randomness when conditioned on the input is still beyond the reach of the CRQS model. We prove that the security of W1TRO cannot be black-box reduced to any assumption that can be framed as a cryptographic game. Our impossibility result employs the simulation paradigm formalized by Wichs (ITCS ’13) and has implications for other cryptographic tasks.
- There is no universal implementation of the Fiat-Shamir transform whose security can be black-box reduced to a cryptographic game assumption. This extends the impossibility result of Bitansky et al. (TCC ’13) to the CRQS model.
- We impose severe limitations on constructions of quantum lightning (Zhandry, Eurocrypt ’19). If a scheme allows n lightning states’ serial numbers (of length m such that n > m) to be combined in such a way that the outcome has entropy, then it implies W1TRO, and thus cannot be black-box reduced to a cryptographic game assumption.
Senior Product Manager
Aspen Technology
Biography
Montreal-based quantum physicist, senior product manager, and full stack developer with strong experience building award-winning hardware and software products. Currently Senior Product Manager at Aspen Technology leading connectivity and AI inference at the Edge. Prior to Aspen Technology, I worked at Machine-To-Machine Intelligence (M2Mi) a leader in IoT Security and Management located at NASA Ames research center in the heart of Silicon Valley.
Prior to M2Mi, built SQR Technologies a belgian quantum based, hardware security startup that pioneered distributed quantum key generation. Acquired by IDQ (Switzerland). Awarded a Ph.D. in Physics (Quantum Cryptography) from the University of Brussels. Research interests include: quantum cloning, experimental quantum cryptography, quantum noise reduction, and quantum random number generation.
10:30 - 10:55 Inscription
10:55 - 11:00 Mot d'ouverture (Salon A)
11:00 - 11:15 Pr. Nicolas Godbout, directeur de l'INTRIQ
11:15 - 11:30 Martin Laforest, ACET
Quantum zone
11:30 - 12:00 Pr. Sébastien Francoeur, Polytechnique Montréal
Turoriel: 2D material essentials: Raman spectroscopy
12:00 - 13:30 Diner (Salle Knowlton)
13:30 - 14:30 Pr. Adina Luican-Mayer, Université d'Ottawa
Quantum 2D materials and devices at the atomic scale
14:30 - 15:00 Pause-café (Salon B)
15:00 - 16:00 Dr. Christoph Stampfer, RWTH Aachen
Towards spin and valley qubits in graphene
16:00 - 17:00 Présentations de l'écosystème quantique
Aimee Gunther, Ph.D., CNRC, Quantum Sensors Program Leader
The National Research Council’s Quantum Sensors
Challenge Program
Karabina Koray, Ph.D., CNRC, Deputy Director, Quantum Sensors
The National Research Council’s Applied Quantum Computing
Challenge Program
Félix Beaudoin, Ph.D., Nanoacademic Technologies Inc.
Director of Quantum Technology
Technology Computer-Aided Design of spin qubits at cryogenic
temperature
M. Olivier Gagnon-Gordillo, Québec quantique
Responsablede la stratégie et du développement
Quantum Ecosystem in Quebec
Dr. Udson Mendes, CMC Microsystems
TeamLeader, Quantum Computing
CMC Microsystems: Democratizing Access to Quantum
Technologies
17:00 - Session d'affiches et rafraichissements (Salon B)
19h30 - Souper INTRIQ (Salle Knowlton)
8:30 - 9:30 Alex Bredariol Grilo, Ph.D., CNRS Sorbonne
Quantum learning algorithms imply circuit lower bounds
9:30 - 10:15 Professeur Kartiek Agarwal, McGill University
Quantum Many-Body Scars and their close associated
with Cellular Automata
10:15 - 11:00 Pause-café (Salon B)
11:00 - 12:00 Christopher Chamberland, Ph.D., Amazon Web Services
Universal fault-tolerant quantum computing with lattice surgery
12:00 - 13:30 Diner (Salle Knowlton)
13:30 - 14:00 Professeur Kartiek Agarwal, McGill University
Tutoriel : Tutorial: What are Majorana Zero Modes?
14:00 - 14:40 Professeur Nicolas Quesada, Polytechnique Montréal
Quantum Computational Advantage via GaussianBoson Sampling
14:40 - 14:50 Break
14:50 - 15:20 Sho Onoe, Postdoc, Polytechnique Montréal
Towards single-shot quantum measurement of both field
quadratures on subcycle time scales
15:20 - 15:40 Simon Bolduc Beaudoin, Ph.D. student, Université de Sherbrooke
Statistics of Broadband Microwave Photons
15:40 - 16:00 Jonathan Durandau, Ph.D. student, Université de Sherbrooke
Two's company, three is a crowd in segmented ion trap quantum
computers
16:00 - 16:25 Questions et réponses
16:25 - 16:30 Mot de clôture
Amazon Web Services
Universal fault-tolerant quantum computing with lattice surgery
Quantum computers hold the promise to solve certain families of problems exponentially faster than classical computers. However, due to high noise rates, building large scale quantum devices remains a significant challenge and will require a fault-tolerant error correction architecture adapted to the hardware. In this talk, I will present new developments into pological error correcting codes with a focus on lattice surgery implementations to build a universal fault-tolerant quantum computer. In particular, I will start by discussing how all gates in quantum algorithms can be decomposed in terms of multi-qubit Pauli measurements and how such measurements can be implemented via lattice surgery. I will then discuss both twist-free and twist-based implementations of lattice surgery, with the former being suitable for broader families of quantum hardware. Next, I will discuss temporal encoding of lattice surgery, which can be used to significantly speed up lattice surgery protocols. Lastly, I will conclude the talk by presenting a core-cache architecture model for a quantum processor.
CNRS Sorbonne
Quantum learning algorithms imply circuit lower bounds
In this talk, I will present the first general connection between the design of quantum algorithms and circuit lower bounds. In our work, we show that non-trivial quantum learning algorithms for circuit classes imply circuit lower bounds, which are sought-after results in classical complexity theory and are connected to key questions in the field such as the P vs. NP question. Our proof builds on several works in learning theory, pseudo randomness, and computational complexity, and crucially, on a connection between non-trivial classical learning algorithms and circuit lower bounds established by Oliveira and Santhanam (CCC 2017). More concretely, we show among other results how pseudorandom generators imply learning-to-lower-bound connections in a generic fashion, construct the first conditional pseudorandom generator secure against uniform quantum computations, and extend the local list-decoding algorithm of Impagliazzo, Jaiswal, Kabanets and Wigderson (SICOMP 2010) to quantum circuits via a delicate analysis. We believe that these contributions are of independent interest and might find other applications.
This is a joint work with Srinivasan Arunachalam, Tom Gur, Igor C. Oliveira, and Aarthi Sundaram.
Department of Physics, University of Ottawa
Quantum 2D materials and devices at the atomic scale
Material systems, devices, and circuits, based on the manipulation of individual charges, spins, and photons in solid-state platforms are key for revolutionary quantum technologies. The burgeoning field of quantum two-dimensional (2D) materials presents an emerging opportunity for breakthroughs in the development of next-generation quantum technologies while also pushing the boundaries of fundamental understanding in condensed matter. Our laboratory aims to create quantum functionality in 2D systems by combining fabrication and assembly techniques of 2D layers with atomically precise scanning probe microscopy.
In this talk, I will focus on scanning tunnelling microscopy and spectroscopy experiments aimed at elucidating the nature of atomic-scale defects in 2D materials [1] and at creating novel moiré structures by twisting 2D layers [2]. I will also discuss our recent results on reversible local response of domain wall networks in ferroelectric interfaces of marginally twisted WS2 bilayers. Secondly, I will present our progress in realizing quantum-confined devices in 2D semiconductors [3].
[1] Phys. Rev. B 102 (20), 205408, (2020)
[2] Journal of Applied Physics, (2020)
[3] Applied Physics Letters 119 (13), 133104(2021) and arXiv preprint arXiv:2203.11871
Department of Engineering Physics, Polytechnique Montréal
Quantum Computational Advantage via Gaussian Boson Sampling
One of the most appealing proposals to demonstrate quantum advantage, when a quantum processor performs calculations far beyond the reach of any classical supercomputer, is Gaussian Boson Sampling. This quantum photonic architecture consists of multiple squeezed light modes which are entangled in an interferometer and are then measured using photon counters. In this talk we discuss prospects and recent claims of photonic quantum computational advantage.
We present two no-go results where we show that programmable Gaussian Boson Samplers with interferometers assembled from lossy nearest neighbour beam splitters cannot be used to demonstrate quantum advantage. When the interferometers are shallow, meaning that any given mode only interacts with very few near neighbours, we provide an efficient classical algorithm for the simulation of GBS [1].
In the opposite limit, when the interferometer is deep and large, we show that the exponential accumulation of loss induced by many layers of lossy beam splitters allows us to approximate the sampling using mixtures of coherent states for which sampling can be performed efficiently [2].
Finally, we discuss our recent proposal [3] to build programmable Gaussian Boson Samplers using beam splitters between distant modes by using fiber delay loops as buffers in time-domain multiplexed architectures. We show that state-of-the-art classical algorithms for simulating our proposed architecture are vastly out performed by potential near-term implementations. This work thus opens the path to demonstrating quantum computational advantage with programmable photonic processors.
[1] Efficient sampling from shallow Gaussian quantum-optical circuits with local interactions. H. Qi, D. Cifuentes, K. Brádler, R. Israel, T. Kalajdzievski, N. Quesada, Phys. Rev. A 105 (5), 052412 (2022)
[2] Regimes of Classical Simulability for Noisy Gaussian Boson Sampling. H. Qi,D. J. Brod, N. Quesada, and R. García-Patrón. Phys. Rev. Lett. 124, 100502 (2020).
[3] Quantum Computational Advantage via High-Dimensional Gaussian Boson Sampling. A. Deshpande, et al., arXiv 2102.12474 . To appear in Science Adv. 8(1), eabi7894 (2022)
JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, Germany
Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Germany
Towards spin and valley qubits in graphene
Graphene and bilayer graphene (BLG) are attractive platforms for quantum circuits with potential applications in the area of quantum information. This has motivated substantial efforts in studying quantum dot devices based on graphene and bilayer graphene. A major challenge in this context is the missing band-gap in graphene, which does not allow to confine electrons by means of electrostatics making displacement field-gapped BLG particularly interesting.
Here we present gate-controlled single and double quantum dots in electrostatically gaped BLG [1-3]. We show a remarkable degree of control of our devices, which allow realizing electron-hole and electron-electron double quantum dot systems with single-electron occupation. In both, the single and double quantum dot devices, we reach the very few electron/hole regime, we are able to extract excited state energies and investigate their evolution in a parallel and perpendicular magnetic field. Finally, I will show data on BLG quantum dots allowing investigating the spin-valley coupling in bilayer graphene [2] as well as spin life times [3]. Our work paves the way for the implementation of spin and valley-qubits in graphene.
[1] S. Möller, L. Banszerus, A.Knothe, C. Steiner, E. Icking, S. Trellenkamp, F. Lentz, K. Watanabe, T.Taniguchi, L. Glazman, V. Fal'ko, C. Volk, and C. Stampfer, Phys. Rev. Lett.127, 256802 (2021)
[2] L. Banszerus,S. Möller, C. Steiner, E. Icking, S. Trellenkamp, F. Lentz, K. Watanabe, T.Taniguchi, C. Volk, and C. Stampfer, Nature Communications 12, 5250 (2021)
[3] L. Banszerus, K. Hecker, S. Möller, E. Icking, K. Watanabe, T. Taniguchi,C. Volk, and C. Stampfer, arXiv: 2110.13051 (2022)
Director of Quantum Technology
NanoacademicTechnologies Inc.
Technology Computer-Aided Design of spin qubits at cryogenic temperature
While quantum technologies promise to deliver disruptive applications in computing, sensing, and secure communications, their performance is determined by the quality of the underlying quantum hardware. Across all implementations and applications, achieving and extending quantum advantage will require many R&D cycles consisting of qubit design, manufacturing, experimental characterization, and data analysis. In the classical semiconductor industry, mature technology computer-aided design (TCAD) software plays a central role in this workflow by enabling to predict and optimize device performance before fabrication, thus accelerating hardware development and reducing R&D costs. Unfortunately, conventional TCAD software does not apply to quantum hardware which is based on completely different physics.
In this presentation, we introduce QTCAD, a new software tool for Quantum-Technology Computer Aided Design to fulfill this role. Thanks to advanced physics-based modeling features and powerful numerical methods, QTCAD enables to simulate spin-qubit hardware to predict device performance before manufacturing, even at cryogenic temperatures required for spin-qubit operation, at which most commercially available TCAD tools fail to converge. During this talk, we will present the key features of QTCAD, namely non-linear Poisson, Schrödinger, many-body, and transport solvers. We will also present representative use cases involving gated quantum dots, and present typical simulation results for gate electrostatics, quantum confinement, transport in the Coulomb blockade regime, Rabi oscillations, and much more.
Québec quantique
Responsablede la stratégie et du développement
Quantum Ecosystem in Quebec
Research Officer - Digital Technologies
National Research Council of Canada
The National Research Council’s Applied Quantum Computing Challenge Program
The National Research Council of Canada is developing a new challenge program for Applied Quantum Computing. The program will collaborate with industry and academia to support commercial innovation to build on Canada's position as a global leader in applied quantum computing. Potential areas of focus include quantum algorithms with applications, quantum simulations of physical systems, and models and architecture of quantum computers. This presentation will provide an overview of the Applied Quantum Computing Challenge program and discuss some future plans.
Deputy Director, Quantum Sensors Challenge Program
National Research Council of Canada
The National Research Council’s Quantum Sensors Challenge Program
As part of the Government of Canada’s Innovation Agenda, The National Research Council of Canada announced its intent to launch a research program to support collaborative research in quantum sensors. Work began to design the program in early 2020. Coinciding with its launch in the spring of 2021, the program received additional funding from Government of Canada’s commitment to building a National Quantum Strategy. This presentation will review the NRC Challenge Program structure, give a high-level overview of the first round of funded projects within the program, and discuss plans for the remaining 6 years of the program.
Team Leader, Quantum Computing
CMC Microsystems
CMC Microsystems: Democratizing Access to Quantum Technologies
CMC’s mission is to democratize access to state-of-the-art quantum hardware and software technologies to different sectors of Canada’s quantum ecosystem. In this talk, I will give a brief overview of CMC’s quantum computing services offered to Canadian academics, Startup’s and industrial clients. These services include access to CAD tools, fabrication of superconducting, CMOS and photonics devices, access to quantum computing systems and training of highly-qualified personnel.
Professor, McGill University
Quantum Many-Body Scars and their close associated with Cellular Automata
We provide a systematic approach for constructing approximate quantum many-body scars(QMBS) starting from two-layer Floquet automaton circuits that exhibit trivial many-body revivals. We do so by applying successively more restrictions that force local gates of the automaton circuit to commute concomitantly more accurately when acting on select scar states. With these rules in place, an effective local, Floquet Hamiltonian is seen to capture dynamics of the automata over along prethermal window, and neglected terms can be used to estimate the relaxation of revivals. We provide numerical evidence for such a picture and use our construction to derive several QMBS models, including the celebrated PXP model.
Professor, McGill University
Tutorial: What are Majorana Zero Modes?
Topology based quantum computing holds immense promise for building scalable quantum devices because it implements protection from errors naturally at the hardware level. A major component of such a future quantum computer are Majorana Zero Modes or Majoranas for short. In this tutorial, I will discuss what Majorana Zero Modes are and how they are important to building topological quantum bits (qubits), how they are realized in materials, the current status of experiments and theory, and the possible ways forward.
Étudiant au doctorat, Université de Sherbrooke
Directeur: Bertrand Reulet
Statistics of Broadband Microwave Photons
Étudiant au doctorat, Université de Sherbrooke
Directeur: Yves Bérubé-Lauzière
Two's company, three is a crowd in segmented ion trap quantum computers
The existence of shuttled ions trap computers whose architectures are linear arrangement of segmented trap has now been proved to be possible and is one of the current studied paths for NISQ quantum computers. There are different ways to expand and perfect the performance of this type of architecture. In this paper we study the impact on the number of ions per trap on quantum algorithm implementation on this type of machine. We will see the hypothesis necessarily so the grows of the number of ions per trap bring a benefice to the implementation, we will also explore the additional difficulty caused by it. We will show through our simulation that the difficulty to implement a greater number of ions may not be balanced by the ease of shuttling brings by it.
Professeur, Polytechnique Montréal
Tutoriel: 2D material essentials: Raman spectroscopy
By exhibiting a rich variety of sometimes spectacular properties, 2D materials have emerged as an important family of materials. If the characterization and development of these materials call fora number of sophisticated techniques and instruments, one of these techniques has played a central and predominant role: Raman spectroscopy. I have discovered this technique along with 2Dmaterials and it hasn’t since cessed to impress me by its formidable versatility and power.
In this short tutorial, I will first present some fundamental aspects of Raman spectroscopy. Then, I will present how it provides critical information on crystal symmetry, layer stacking, phonon confinement, oxidation, and defects. I will present a few compelling examples on how Raman spectroscopy can be used to study electron-phonon coupling, resonant electronic and excitonic states, and hyperbolic polaritons. Finally, I will show how Raman processes, in addition to probing a large variety of solid-state excitations, be used to coherently control quantum states.
Postdoc, Polytechnique Montréal
Directeur: Denis Seletskiy
Towards single-shot quantum measurement of bothfield quadratures on subcycle timescales
A classical picture of the dispersive electro-optic sampling has been introduced as a single-shot measurement technique to measure the electric field in the time-domain. In this picture, the number of datapoints in the time-domain is restricted by the number of pixels that can be measured by the camera. We reformulate this technique into the quantum regime by considering an ultra-broadband probe, replacing the detection method with dispersive Fourier transform and introducing the post-processing that is required to measure both quadratures; the electric field and its conjugate. This requires a more accurate treatment of dispersive elements in the electro-optic sampling such as the nonlinear crystal and the achromatic waveplate, which we incorporate in the post-processing analysis on a pulse-by-pulse basis.
Doctorant, Polytechnique Montréal
Directeur: Oussama Moutanabbir
Dynamically Modulated Polarization-Induced Transparency in Group-IV Core/Shell Nanowire Arrays
We demonstrate theoretically and experimentally an analogue of electromagnetically-induced transparency at short-wave infrared frequencies in an all-dielectric metasurface system that consists of a two-dimensional Si/GeSn core/shell naowire array on top of a silicon substrate. By varying the incident light polarization, we show that the reflectance feature of the array system can be efficiently engineered due to multipolar interference driven by the electric and magnetic dipole interactions.
Étudiant au doctorat, CNRC - Ottawa
Directeur: Louis Gaudreau
Quantum confinement in 2D heterostructures
Quantum confinement in two-dimensional (2D) transition metal dichalcogenides (TMDs) offers the opportunity to create unique quantum states that can be practical for quantum technologies. The interplay between charge carrier spin and valley, as well as the possibility to address their quantum states electrically and optically, makes 2D TMDs an emerging platform for the development of quantum devices.
In this poster session, we present the fabrication of a fully encapsulated monolayer tungsten diselenide (WSe2) based device in which we realize gate-controlled hole quantum dots. We demonstrate how our device architecture allows us to identify and control the quantum dots formed in the local minima of electrostatic potential fluctuations in the WSe2 using gates. Coulomb blockade peaks and diamonds are observed which allow us to extract information about the dot diameter and its charging energy. Furthermore, we demonstrate how the transport passing through the channel formed by two gates is sensitive to the occupation of a nearby quantum dot. Additionally, we show how this channel can be tuned to be in the charge detection or the Coulomb blockade regime. Finally, we present a new device architecture which exhibits quantized conductance plateaus over a channel length of 600 nm at a temperature of 4 K. Quantized conductance over such a long channel provides an opportunity to incorporate gate defined quantum dot circuits without the nuisance of inhomogeneity within the channel.
Étudiant à la maîtrise, Ottawa University
Directrice: Anne Broadbent
Boîtes Non-Locales en Information Quantique
Au jeu CHSH, les stratégies quantiques sont limitées par la borne de Tsirelson, à ~85% de réussite maximale à ce jeu. Mais, les stratégies post-quantiques, formalisées par les boîtes non-locales, peuvent aller jusqu'à 100%. On aimerait donner un critère pour expliquer pourquoi ces boîtes sont invraisemblables dans la Nature, et l'on conjecture que ce critère est la complexité de communication. En effet, on sait déjà que les corrélations quantiques engendrent un complexité de communication non-triviale, et qu'au contraire les boîtes non-locales qui gagnent à CHSH avec ≥ 91% rendent triviale la complexité de communication (2006). Question ouverte : qu'en est-il des autres boîtes non-locales ?Si on arrive à montrer que les autres boîtes non-locales rendent aussi triviale la complexité de communication, alors on aura une explication pour la présence de la borne de Tsirelson : c'est parce que la complexité de communication doit rester non-triviale pour qu'une stratégie soit possible dans la Nature.
Étudiant à la maîtrise, Université de Sherbrooke
Directeur: Michel Pioro-Ladrière
Organisation de l’instrumentation pour acheminer les signaux de contrôle sans pièces de conditionnement cryogénique, à l’aide de câble spécialement conçu pour la combinaison de signaux à température ambiante
Intégrer l’initialisation des échantillons de qubit de spin sous un appareil qui peut mesurer le courant de fuite ainsi que générer des hautes tensions. Cette instrument servira pour automatiser, réduire le temps d’analyse ainsi que permettre de développer de nouveau algorithme et forme d’onde pour obtenir plus rapidement le régime à un électron.
Étudiant à la maîtrise, Ottawa University
Directrice: Anne Broadbent
Rigidity for Monogamy-of-Entanglement Games
In a monogamy-of-entanglement (MoE) game, two players who do not communicate try to simultaneously guess a referee's measurement outcome on a shared quantum state they prepared. We study the prototypical example of a game where the referee measures in either the computational or Hadamard basis and informs the players of her choice.
We show that this game satisfies a rigidity property similar to what is known for some nonlocal games. That is, in order to win optimally, the players' strategy must be of a specific form, namely a convex combination of four unentangled optimal strategies generated by the Breidbart state. We extend this to show that strategies that win near-optimally must also be near an optimal state of this form. We also show rigidity for multiple copies of the game played in parallel.
As an application, we construct for the first time a weak string erasure scheme where the security does not rely on limitations on the parties' hardware. Instead, we add a prover, which enables security via the rigidity of this MoE game. Furthermore, we show that this can be used to achieve bit commitment in a model where it is impossible classically.
Doctorant, Polytechnique Montréal
Directeur: Oussama Moutanabbir
Electric-dipole spin resonance for light-holesin direct bandgap germanium quantum well
Doctorant, Université de Sherbrooke
Directeur: Bertrand Reulet
Fluctuation Loops in microwave circuits
Fluctuation loops are average trajectories that can be observed in noise driven out of equilibrium systems. In electronic circuits they can be observed by measuring two voltages and averaging all trajectories between any pair of points in the resulting (V1,V2) space. The trajectories them selves and other related time domain metric allow us to quantify how much a circuit is breaking equilibrium and its application to microwave circuits paves the way for measurements in the quantum regime.
Étudiant à la maîtrise, Université de Sherbrooke
Director: Bertrand Reulet
Sujet à venir
Doctorant, McGill University
Directeur: Bill Coish
Generalized fast quasi-adiabatic population transfer for improved qubit readout, shuttling, and noise mitigation
Population-transfer schemes are commonly used to convert information robustly stored in some quantum system for manipulation and memory into more macroscopic degrees of freedom for measurement. These schemes may include, e.g., spin-to-charge conversion for spins in quantum dots, detuning of charge qubits between a noise-insensitive operating point and a measurement point, spatial shuttling of qubits encoded in spins or ions, and parity-to-charge conversion schemes for qubits based on Majorana zero modes. A common strategy is to use a slow (adiabatic) conversion. However, in an adiabatic scheme, the adiabaticity conditions on the one hand, and accumulation of errors through dephasing, leakage, and energy relaxation processes on the other hand, limit the fidelity that can be achieved. Here, we give explicit fast quasi-adiabatic (fast-QUAD) conversion strategies (pulse shapes) beyond the adiabatic approximation that allow for optimal state conversion. In contrast with many other approaches, here we account for a general source of noise in combination with pulse shaping. Inspired by analytic methods that have been developed for dynamical decoupling theory, we provide a general framework for unique noise mitigation strategies that can be tailored to the system and environment of interest.
Étudiant à la maîtrise, Polytechnique Montréal
Directeur: Oussama Moutanabbir
Coherent control in Mid-Infrared
GeSn is a silicon-compatible semiconductor of great interest because of the possibility to engineer the bandgap directness and its energy in the mid-infrared, and the potential for designing monolithic photonic and optoelectronic devices. In this work, we exploit the recent developments made in establishing high-quality, direct bandgap GeSn layers, to investigate the optical injection and coherent control of charge and spin currents in this group IV semiconductor. The study of these processes could play a key role in the development of coherent photon-to-spin interfaces, long-sought after for entanglement distribution, and may have innovative applications in biochemical quantum sensing due to the access to the mid-infrared region. To this end, a full zone 30-band k·p model is applied to obtain the band structure of relaxed GeSn. For one- and two-photon absorption, the optical injection of carrier, spin, current, and spin current are calculated in the independent particle approximation. Critical properties such as the two-photon absorption anisotropy and linear-circular dichroism are also extracted. Finally, coherent control with a bichromatic field of frequencies ω and 2ω is investigated. In this case, with the incorporation of Sn in Ge, we find a significant increase of charge current injection at energies close to the band gap, and of spin current injection for a relatively broad range of energies.
Doctorant, Unviersité de Sherbrooke
Directeur: Alexandre Blais
Realistic simulation of the first 17-qubit surface code experiment
Thesurface code is a prominent candidate for the realization of quantum errorcorrection with superconducting qubits due to its suitable 2D-gridqubit-arrangement and its relatively high error tolerance. To guide efforts inimproving the code ability to preserve logical states, it is necessary toperform realistic modeling of the system based on experimentally informativedevice characteristics such as individual qubit coherence times, cross-Kerrinteractions, and gate fidelities. Here, we solve the complete time-evolutionof a 17-qubit device implementing a distance-3 surface code using a Monte Carlowave function approach. We also implement an effective model that captures allthe desired dynamics while significantly reducing the computationalrequirements. Using this approach, we analyze the expected code performance asa function of experimentally relevant qubit parameters and their non-uniformdistribution on the device. We also investigate the optimal parameterimprovements needed to enhance logical state preservation and to reach thethreshold.
Étudiante à la maîtrise, Université de Sherbrooke
Directeur: Michel Pioro-Ladrière
Preparation of a cat state in a superconducting circuit
Encoding information into the naturally large Hilbert space of an harmonic oscillator allows complex states of the light to be considered as a logical basisand used for quantum error correction codes [1]. Through mapping the state of a single qubit onto the state of a cavity, we can obtain multiphoton states known as cat states [2,3,4]. Here, we present an implementation of the qubit cavity mapping protocol (qcMAP) [4,5] using a transmon as an ancilla qubit and a coaxial cavity to store the encoded state. With this hardware, we reach a preparation fidelity of 93%, primarily limited by the relaxation and decoherence time of the transmon and the cavity self-Kerr.
[1]W. Cai et. al., Fundam. Res. 1, 50-67(2021)
[2] N. Ofek, A.Petrenkoet.al., Nature 536, 441-445 (2016)
[3] S. Haroche and J-M.Raimond, Exploring the Quantum (2006)
[4] B. Vlastakis et.al.,Science 342, 6158 (2013)
[5] Z. Leghtas et.al., PRA 87, 042315 (2013)
Étudiant à la maîtrise, McGill University
Directeur: Bill Coish
Jackiw Rebbi Magnons
We theoretically study the elementary excitations of a magnetic topological insulator. These excitations combine aspects of Jackiw-Rebbi bound states and magnon modes. Specifically, we consider the delocalized excitations of a quantum ferromagnet in contact with a 2D Dirac electron system. The local magnetization gaps the electron system, leading to bound states at magnetic domain walls (Jackiw-Rebbi modes). The delocalized (magnon) excitations of this system thus inherit a charge from the delocalized Jackiw-Rebbi bound states. We show that these composite excitations (Jackiw-Rebbi magnons) can be probed experimentally through the characteristic chiral current distribution, and through unique characteristics of the transverse spin susceptibilities.
Étudiant à la maîtrise, CNRC - Ottawa
Directeur: Louis Gaudreau
Coherent driving of a single heavy hole qubit in a GaAs/AlGaAs double quantum dot device
Étudiant à la maîtrise, Université de Sherbrooke
Directrice: Eva Dupont-Ferrier
Sujet à venir
PhD student, NRC - Ottawa
Director: Louis Gaudreau
Reversible local response of domain wall networks inferroelectric interfaces of marginally twisted WS2 bilayers
Laurent Molino (1), Leena Aggarwal (1), Vladimir Enaldiev (3), Ryan Plumadore (1), Vladimir Falko (2,3,4), Adina Luican-Mayer (1)*
1 Department of Physics, Universityof Ottawa, Ottawa, Canada
2 National Graphene Institute,University of Manchester, Manchester, UK
3 Department of Physics and Astronomy, University of Manchester, Manchester, UK
4 Henry Royce Institute for AdvancedMaterials, University of Manchester, Manchester, UK
Semiconducting ferroelectric materials with low energy polarisation switching offer a platform for next-generation electronics such as ferroelectric field-effect transistors. Ferroelectric domains at symmetry-broken interfaces of transition metal dichalcogenide films provide an opportunity to combine the potential of semiconducting ferroelectrics with the adaptability of two-dimensional material devices. Here, local control of ferroelectric domains in a marginally twisted WS2 bilayer is demonstrated with a scanning tunneling microscope, and their observed reversible evolution understood using a string-like model of the domain wall network. We identify two characteristic regimes of domain evolution: (i) elastic bending of partial screw dislocations separating smaller domains with twin stacking and (ii) formation of perfect screw dislocations by merging pairs of primary domain walls. We also show that the latter act as the seeds for the reversible restoration of the inverted polarisation.
Étudiant à la maîtrise, Université de Sherbrooke
Directeur: Michel Pioro-Ladrière
Toolbox for fast tuning of spin qubits into the single electron regime
Initializing a spin qubit device into its operating regime is a long and arduous process. Each gate has to be manually tuned to a very precise value ina large gate voltage space and measuring a single stability diagram can take upto an entire day. Thus, tools to automate part of the tuning process and speedup measurements are presented. By combining statistical analysis, machine learning techniques, high performance instrumentation and unconventionnal measuring techniques, we can optimize the process of finding the single electron regime in a single dot stability diagram while reducing the amount data needed to do so.
Étudiant à la maîtrise, Université de Sherbrooke
Director: Bertrand Reulet
Characterisation of localized defects in hBN: en route to a quantumlight emitting diode (QLED)
hBN, a large-gap van der Waals material, hosts stable, single photon emitters (SPEs) in the visible, making it a promising platform for quantum photonics [1]. The optical properties of the sesingle photon emitters have been the subject of several studies, but their electrical and optoelectronic properties are still largely unexplored. Here, such properties are investigated, with photoluminescence (PL) mapping, spectroscopy (5K to 300K) and lifetime measurements. Preliminary results indicate multiple sharp and localized luminescent defects exhibiting characteristic single photon emitter behaviors. However, defects are highly concentrated on the hBN flakes, generating an intense background emission. Further investigation of defect engineering, reducing the defect density, must be done before getting into time correlated measurements and optoelectronic control, which could pave the way for the development of an electrically pumped single-photon source.
[1]Tran al., Nat. Nanotechnol., 11 (2016).
Doctorant, McGill Unversity
Directrice: Lilian Childress
A Fiber-Based Microcavity Coupled to a Colour Center in Diamond
Color centers indiamond are promising solid-state spin-qubit systems for quantum informationthanks to their atom-like spin-optical properties. Two prospective candidates are the nitrogen-vacancy (NV) and germanium-vacancy (GeV). Current implementations with the NV center are restricted by its low emission rate (3%) into its coherent transition and spectral diffusion. In turn, the use ofthe GeV is limited by its spin-orbit interaction necessitating low-temperature operation. We present our current results in coupling a fiber-based openmicrocavity (measured finesse of F~8000) to a GeV at ~ 15K. Achieving a reduced lifetime of 3.28+/-0.03 ns (6 ns) and an expected Purcell Enhancement of the zero-phonon line of 11 +/-4.
Étudiant à la maîtrise, McGill University
Directeur: Kartiek Agarwal
Scars and Fragmented Hamiltonians from Automaton circuits
We provide a systematic approach for constructing approximate quantum many-body scars (QMBS) starting from two-layer Floquet automaton circuits that exhibit trivial many-body revivals. We do so by applying successively more restrictions that force local gates of the automaton circuit to commute concomitantly more accurately when acting on select scar states. With these rules in place, an effective local, Floquet Hamiltonian is seen to capture dynamics of the automata over a long prethermal window, and neglected terms can be used to estimate the relaxationof revivals. We provide numerical evidence for such a picture and use our construction to derive several QMBS models, including the celebrated PXP model.
Michael J Gullans (Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, Maryland 20742 USA)NSERCGrants RGPIN-2019-06465, and DGECR- 2019-00011, Tomlinson Scholar Fund
Doctorant, Université de Sherbrooke
Directeur: Alexandre Blais
Dynamics of Transmon Ionization
Qubitmeasurement and control in circuit QED rely on microwave drives, with higherdrive amplitudes ideally leading to faster processes. However, degradation inqubit coherence time and readout fidelity has been observed even under moderatedrive amplitudes corresponding to few photons populating the measurementresonator. Here, we numerically explore the dynamics of a driventransmon-resonator system under strong and nearly resonant measurement drives,and find clear signatures of transmon ionization where the qubit escapes out ofits cosine potential. Using a semiclassical model, we interpret this ionizationas resulting from resonances occurring at specific resonator photonpopulations. We find that the photon populations at which these spurioustransitions occur are strongly parameter dependent and that they can occur atlow resonator photon population, something which may explain the experimentallyobserved degradation in measurement fidelity.
Doctorant, Université de Sherbrooke
Directeur: Mathieu Juan
An all-fiber solution to single-photon emission and collection
Quantum light sources producing on-demand streams of single photons arean integral part of photonic systems in applications such as linear optical quantum computing and quantum communications. So far, three main approaches for the hybrid integration of single-photon sources (SPSs) offer the necessary flexibility to meet the stringent requirements of most quantum applications, namely wafer-bonding, transfer-printing and the pick-and-place technique. Here, we propose another avenue to fabricate SPSs directly into optical fibers. We present numerical results predicting that such all-fiber SPSs could operate in the weak-coupling regime of waveguide quantum electrodynamics as well as offer high photon collection efficiency. We fabricated and characterized the first microstructured polymer optical fibers (hMOFs) homogeneously doped with colloidal quantum dots (cQDs). However, time-correlated single photon counting measurements found no significant change in the radiative decay rate for this first generation of cQD-overdoped hMOFs.
Doctorante, Université de Sherbrooke
Directeur: Michel Pioro-Ladrière
Sujet à venir
Doctorant, Ottawa University
Directrice: Anne Broadbent
Device-independent Oblivious Transfer from the Bounded-Quantum-Storage-Model and Computational Assumptions
We present a device-independent protocol for oblivious transfer (DIOT) in the bounded-quantum-storage-model, and analyze its security. Our protocol is everlastingly secure and aims to be more practical than previous DIOT protocols, since it does not require non-communication assumptions that are typical from protocols that use Bell inequality violations; instead, the device-independence comes from a recent self-testing protocol which makes use of a post-quantum computational assumption.
10:30 - 10:55 Registration
10:55 - 11:00 Opening remarks (Salon A)
11:00 - 11:15 Pr. Nicolas Godbout, INTRIQ director
11:15 - 11:30 Martin Laforest, ACET
Quantum zone
11:30 - 12:00 Pr. Sébastien Francoeur, Polytechnique Montréal
Tutorial: 2D material essentials: Raman spectroscopy
12:00 - 13:30 Lunch (Knowlton room)
13:30 - 14:30 Pr. Adina Luican-Mayer, University of Ottawa
Quantum 2D materials and devices at the atomic scale
14:30 - 15:00 Coffee break (Salon B)
15:00 - 16:00 Dr. Christoph Stampfer, RWTH Aachen, Germany
Towards spin and valley qubits in graphene
16:00 - 17:00 Presentations by the Quantum ecosystem
Dr. Aimee Gunther, NRC, Deputy Director, Quantum Sensors
The National Research Council’s Quantum Sensors
Challenge Program
Dr. Karabina Koray, NRC, Research Officer - Digital Technologies
The National Research Council’s Applied Quantum Computing
Challenge Program
Dr. Félix Beaudoin, Nanoacademic Technologies Inc.
Director of Quantum Technology
Technology Computer-Aided Design of spin qubits at cryogenic
temperature
Mr. Olivier Gagnon-Gordillo, Québec quantique
Lead, Strategy and Development
Quantum Ecosystem in Quebec
Dr. Udson Mendes, CMC Microsystems
TeamLeader, Quantum Computing
CMC Microsystems: Democratizing Access to Quantum
Technologies
17:00 - Poster session with refreshments (Salon B)
19:30 - INTRIQ dinner (Knowlton room)
8:30 - 9:30 Dr. Alex Bredariol Grilo, CNRS Sorbonne
Quantum learning algorithms imply circuit lower bounds
9:30 - 10:15 Pr. Kartiek Agarwal, McGill University
Quantum Many-Body Scars and their close associated
with Cellular Automata
10:15 - 11:00 Coffee break (Salon B)
11:00 - 12:00 Dr. Christopher Chamberland, Amazon Web Services
Universal fault-tolerant quantum computing with lattice surgery
12:00 - 13:30 Lunch (Knowlton room)
13:30 - 14:00 Pr. Kartiek Agarwal
Tutorial : What are Majorana Zero Modes?
14:00 - 14:40 Pr Nicolas Quesada
Quantum Computational Advantage via Gaussian Boson Sampling
14:40 - 14:50 Break
14:50 - 15:20 Sho Onoe, Postdoc, Polytechnique Montréal
Towards single-shot quantum measurement of both field
quadratures on subcycle time scales
15:20 - 15:40 Simon Bolduc Beaudoin, Ph.D. student, Université de Sherbrooke
Statistics of Broadband Microwave Photons
15:40 - 16:00 Jonathan Durandau, Ph.D. student, Université de Sherbrooke
Two's company, three is a crowd in segmented ion trap quantum
computers
16:00 - 16:25 Questions and answers
16:25 - 16:30 Closing remarks
Amazon Web Services
Universal fault-tolerant quantum computing with lattice surgery
Quantum computers hold the promise to solve certain families of problems exponentially faster than classical computers. However, due to high noise rates, building large scale quantum devices remains a significant challenge and will require a fault-tolerant error correction architecture adapted to the hardware. In this talk, I will present new developments into pological error correcting codes with a focus on lattice surgery implementations to build a universal fault-tolerant quantum computer. In particular, I will start by discussing how all gates in quantum algorithms can be decomposed in terms of multi-qubit Pauli measurements and how such measurements can be implemented via lattice surgery. I will then discuss both twist-free and twist-based implementations of lattice surgery, with the former being suitable for broader families of quantum hardware. Next, I will discuss temporal encoding of lattice surgery, which can be used to significantly speed up lattice surgery protocols. Lastly, I will conclude the talk by presenting a core-cache architecture model for a quantum processor.
CNRS Sorbonne
Quantum learning algorithms imply circuit lower bounds
In this talk, I will present the first general connection between the design of quantum algorithms and circuit lower bounds. In our work, we show that non-trivial quantum learning algorithms for circuit classes imply circuit lower bounds, which are sought-after results in classical complexity theory and are connected to key questions in the field such as the P vs. NP question. Our proof builds on several works in learning theory, pseudo randomness, and computational complexity, and crucially, on a connection between non-trivial classical learning algorithms and circuit lower bounds established by Oliveira and Santhanam (CCC 2017). More concretely, we show among other results how pseudorandom generators imply learning-to-lower-bound connections in a generic fashion, construct the first conditional pseudorandom generator secure against uniform quantum computations, and extend the local list-decoding algorithm of Impagliazzo, Jaiswal, Kabanets and Wigderson (SICOMP 2010) to quantum circuits via a delicate analysis. We believe that these contributions are of independent interest and might find other applications.
This is a joint work with Srinivasan Arunachalam, Tom Gur, Igor C. Oliveira, and Aarthi Sundaram.
Department of Physics, University of Ottawa
Quantum 2D materials and devices at the atomic scale
Material systems, devices, and circuits, based on the manipulation of individual charges, spins, and photons in solid-state platforms are key for revolutionary quantum technologies. The burgeoning field of quantum two-dimensional (2D) materials presents an emerging opportunity for breakthroughs in the development of next-generation quantum technologies while also pushing the boundaries of fundamental understanding in condensed matter. Our laboratory aims to create quantum functionality in 2D systems by combining fabrication and assembly techniques of 2D layers with atomically precise scanning probe microscopy.
In this talk, I will focus on scanning tunnelling microscopy and spectroscopy experiments aimed at elucidating the nature of atomic-scale defects in 2D materials [1] and at creating novel moiré structures by twisting 2D layers [2]. I will also discuss our recent results on reversible local response of domain wall networks in ferroelectric interfaces of marginally twisted WS2 bilayers. Secondly, I will present our progress in realizing quantum-confined devices in 2D semiconductors [3].
[1] Phys. Rev. B 102 (20), 205408, (2020)
[2] Journal of Applied Physics, (2020)
[3] Applied Physics Letters 119 (13), 133104(2021) and arXiv preprint arXiv:2203.11871
Department of Engineering Physics, Polytechnique Montréal
Quantum Computational Advantage via Gaussian Boson Sampling
One of the most appealing proposals to demonstrate quantum advantage, when a quantum processorperforms calculations far beyond the reach of any classical supercomputer, isGaussian Boson Sampling. This quantum photonic architecture consists of multiple squeezed light modes which are entangled in an interferometer and are then measured using photon counters.
In this talk we discuss prospects and recent claims of photonic quantum computational advantage.
We present two no-go results where we show that programmable Gaussian Boson Samplers with interferometers assembled from lossy nearest neighbour beam splitters cannot be used to demonstrate quantum advantage.
When the interferometers are shallow, meaning that any given mode only interacts with very few near neighbours, we provide an efficient classical algorithm for the simulation of GBS [1].
In the opposite limit, when the interferometer is deep and large, we show that the exponential accumulation of loss induced by many layers of lossy beam splitters allows us to approximate the sampling using mixtures of coherentstates for which sampling can be performed efficiently [2].
Finally, we discuss our recent proposal [3] to build programmable Gaussian Boson Samplers using beam splitters between distant modes by using fiber delay loops as buffers in time-domain multiplexed architectures.
We show that state-of-the-art classical algorithms for simulating our proposed architecture are vastly out performed by potential near-term implementations. This work thus opens the path to demonstrating quantum computational advantage with programmable photonic processors.
[1] Efficient sampling from shallow Gaussian quantum-optical circuits with local interactions. H. Qi, D. Cifuentes, K. Brádler, R. Israel, T. Kalajdzievski, N. Quesada, Phys. Rev. A 105 (5), 052412 (2022)
[2] Regimes of Classical Simulability for Noisy Gaussian Boson Sampling. H. Qi,D. J. Brod, N. Quesada, and R. García-Patrón. Phys. Rev. Lett. 124, 100502 (2020).
[3] Quantum Computational Advantage via High-Dimensional Gaussian Boson Sampling. A. Deshpande, et al., arXiv 2102.12474 . To appear in Science Adv. 8(1), eabi7894 (2022)
JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, Germany
Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Germany
Towards spin and valley qubits in graphene
Graphene and bilayer graphene (BLG) are attractive platforms for quantum circuits with potential applications in the area of quantum information. This has motivated substantial efforts in studying quantum dot devices based on graphene and bilayer graphene. A major challenge in this context is the missing band-gap in graphene, which does not allow to confine electrons by means of electrostatics making displacement field-gapped BLG particularly interesting.
Here we present gate-controlled single and double quantum dots in electrostatically gaped BLG [1-3]. We show a remarkable degree of control of our devices, which allow realizing electron-hole and electron-electron double quantum dot systems with single-electron occupation. In both, the single and double quantum dot devices, we reach the very few electron/hole regime, we are able to extract excited state energies and investigate their evolution in a parallel and perpendicular magnetic field. Finally, I will show data on BLG quantum dots allowing investigating the spin-valley coupling in bilayer graphene [2] as well as spin life times [3]. Our work paves the way for the implementation of spin and valley-qubits in graphene.
[1] S. Möller, L. Banszerus, A.Knothe, C. Steiner, E. Icking, S. Trellenkamp, F. Lentz, K. Watanabe, T.Taniguchi, L. Glazman, V. Fal'ko, C. Volk, and C. Stampfer, Phys. Rev. Lett.127, 256802 (2021)
[2] L. Banszerus,S. Möller, C. Steiner, E. Icking, S. Trellenkamp, F. Lentz, K. Watanabe, T.Taniguchi, C. Volk, and C. Stampfer, Nature Communications 12, 5250 (2021)
[3] L. Banszerus, K. Hecker, S. Möller, E. Icking, K. Watanabe, T. Taniguchi,C. Volk, and C. Stampfer, arXiv: 2110.13051 (2022)
Director of Quantum Technology
NanoacademicTechnologies Inc.
Technology Computer-Aided Design of spin qubits at cryogenic temperature
While quantum technologies promise to deliver disruptive applications in computing, sensing, and secure communications, their performance is determined by the quality of the underlying quantum hardware. Across all implementations and applications, achieving and extending quantum advantage will require many R&D cycles consisting of qubit design, manufacturing, experimental characterization, and data analysis. In the classical semiconductor industry, mature technology computer-aided design (TCAD) software plays a central role in this workflow by enabling to predict and optimize device performance before fabrication, thus accelerating hardware development and reducing R&D costs. Unfortunately, conventional TCAD software does not apply to quantum hardware which is based on completely different physics.
In this presentation, we introduce QTCAD, a new software tool for Quantum-Technology Computer Aided Design to fulfill this role. Thanks to advanced physics-based modeling features and powerful numerical methods, QTCAD enables to simulate spin-qubit hardware to predict device performance before manufacturing, even at cryogenic temperatures required for spin-qubit operation, at which most commercially available TCAD tools fail to converge. During this talk, we will present the key features of QTCAD, namely non-linear Poisson, Schrödinger, many-body, and transport solvers. We will also present representative use cases involving gated quantum dots, and present typical simulation results for gate electrostatics, quantum confinement, transport in the Coulomb blockade regime, Rabi oscillations, and much more.
Québec quantique
Lead, Strategy and Development
Quantum Ecosystem in Quebec
Research Officer - Digital Technologies
National Research Council of Canada
The National Research Council’s Applied Quantum Computing Challenge Program
The National Research Council of Canada is developing a new challenge program for Applied Quantum Computing. The program will collaborate with industry and academia to support commercial innovation to build on Canada's position as a global leader in applied quantum computing. Potential areas of focus include quantum algorithms with applications, quantum simulations of physical systems, and models and architecture of quantum computers. This presentation will provide an overview of the Applied Quantum Computing Challenge program and discuss some future plans.
Deputy Director, Quantum Sensors Challenge Program
National Research Council of Canada
The National Research Council’s Quantum Sensors Challenge Program
As part of the Government of Canada’s Innovation Agenda, The National Research Council of Canada announced its intent to launch a research program to support collaborative research in quantum sensors. Work began to design the program in early 2020. Coinciding with its launch in the spring of 2021, the program received additional funding Government of Canada’s commitment to building a National Quantum Strategy. This presentation will review the NRC Challenge Program structure, give ahigh-level overview of the first round of funded projects within the program, and discuss plans for the remaining 6 years of the program.
Team Leader, Quantum Computing
CMC Microsystems
CMC Microsystems: Democratizing Access to Quantum Technologies
CMC’s mission is to democratize access to state-of-the-art quantum hardware and software technologies to different sectors of Canada’s quantum ecosystem. In this talk, I will give a brief overview of CMC’s quantum computing services offered to Canadian academics, Startup’s and industrial clients. These services include access to CAD tools, fabrication of superconducting, CMOS and photonics devices, access to quantum computing systems and training of highly-qualified personnel.
Professor, McGill University
Quantum Many-Body Scars and their close associated with Cellular Automata
We provide a systematic approach for constructing approximate quantum many-body scars(QMBS) starting from two-layer Floquet automaton circuits that exhibit trivial many-body revivals. We do so by applying successively more restrictions that force local gates of the automaton circuit to commute concomitantly more accurately when acting on select scar states. With these rules in place, an effective local, Floquet Hamiltonian is seen to capture dynamics of the automata over along prethermal window, and neglected terms can be used to estimate the relaxation of revivals. We provide numerical evidence for such a picture and use our construction to derive several QMBS models, including the celebrated PXP model.
Professor, McGill University
Tutorial: What are Majorana Zero Modes?
Topology based quantum computing holds immense promise for building scalable quantum devices because it implements protection from errors naturally at the hardware level. A major component of such a future quantum computer are Majorana Zero Modes or Majoranas for short. In this tutorial, I will discuss what Majorana Zero Modes are and how they are important to building topological quantum bits (qubits), how they are realized in materials, the current status of experiments and theory, and the possible ways forward.
PhD student, Université de Sherbrooke
Director: Bertrand Reulet
Statistics of Broadband Microwave Photons
PhD student, Université de Sherbrooke
Director: Yves Bérubé-Lauzière
Two's company, three is a crowd in segmented ion trap quantum computers
The existence of shuttled ions trap computers whose architectures are linear arrangement of segmented trap has now been proved to be possible and is one of the current studied paths for NISQ quantum computers. There are different ways to expand and perfect the performance of this type of architecture. In this paper we study the impact on the number of ions per trap on quantum algorithm implementation on this type of machine. We will see the hypothesis necessarily so the grows of the number of ions per trap bring a benefice to the implementation, we will also explore the additional difficulty caused by it. We will show through our simulation that the difficulty to implement a greater number of ions may not be balanced by the ease of shuttling brings by it.
Professeur, Polytechnique Montréal
Tutoriel: 2D material essentials: Raman spectroscopy
By exhibiting a rich variety of sometimes spectacular properties, 2D materials have emerged as an important family of materials. If the characterization and development of these materials call fora number of sophisticated techniques and instruments, one of these techniques has played a central and predominant role: Raman spectroscopy. I have discovered this technique along with 2Dmaterials and it hasn’t since cessed to impress me by its formidable versatility and power.
In this short tutorial, I will first present some fundamental aspects of Raman spectroscopy. Then, I will present how it provides critical information on crystal symmetry, layer stacking, phonon confinement, oxidation, and defects. I will present a few compelling examples on how Raman spectroscopy can be used to study electron-phonon coupling, resonant electronic and excitonic states, and hyperbolic polaritons. Finally, I will show how Raman processes, in addition to probing a large variety of solid-state excitations, be used to coherently control quantum states.
Postdoc, Polytechnique Montréal
Director: Denis Seletskiy
Towards single-shot quantum measurement of bothfield quadratures on subcycle time scales
A classical picture of the dispersive electro-optic sampling has been introduced as a single-shot measurement technique to measure the electric field in the time-domain. In this picture, the number of data points in the time-domain is restricted by the number of pixels that can be measured by the camera. We reformulate this technique into the quantum regime by considering an ultra-broad band probe, replacing the detection method with dispersive Fourier transform and introducing the post-processing that is required to measure both quadratures; the electric field and its conjugate. This requires a more accurate treatment of dispersive elements in the electro-optic sampling such as the nonlinear crystal and the achromatic waveplate, which we incorporate in the post-processing analysis on a pulse-by-pulse basis.
PhD student, Polytechnique Montréal
Director: Oussama Moutanabbir
Dynamically Modulated Polarization-Induced Transparency in Group-IV Core/Shell Nanowire Arrays
We demonstrate theoretically and experimentally an analogue of electromagnetically-induced transparency at short-wave infrared frequencies in an all-dielectric metasurface system that consists of a two-dimensional Si/GeSn core/shell naowire array on top of a silicon substrate. By varying the incident light polarization, we show that the reflectance feature of the array system can be efficiently engineered due to multipolar interference driven by the electric and magnetic dipole interactions.
PhD student, NRC - Ottawa
Director: Louis Gaudreau
Quantum confinement in 2D heterostructures
Quantum confinement in two-dimensional (2D) transition metal dichalcogenides (TMDs) offers the opportunity to create unique quantum states that can be practical for quantum technologies. The interplay between charge carrier spin and valley, as well as the possibility to address their quantum states electrically and optically, makes 2D TMDs an emerging platform for the development of quantum devices.
In this poster session, we present the fabrication of a fully encapsulated monolayer tungsten diselenide (WSe2) based device in which we realize gate-controlled hole quantum dots. We demonstrate how our device architecture allows us to identify and control the quantum dots formed in the local minima of electrostatic potential fluctuations in the WSe2 using gates. Coulomb blockade peaks and diamonds are observed which allow us to extract information about the dot diameter and its charging energy. Furthermore, we demonstrate how the transport passing through the channel formed by two gates is sensitive to the occupation of a nearby quantum dot. Additionally, we show how this channel can be tuned to be in the charge detection or the Coulomb blockade regime. Finally, we present a new device architecture which exhibits quantized conductance plateaus over a channel length of 600 nm at a temperature of 4 K. Quantized conductance over such a long channel provides an opportunity to incorporate gate defined quantum dot circuits without the nuisance of inhomogeneity within the channel.
Master student, Ottawa University
Director: Anne Broadbent
Boîtes Non-Locales en Information Quantique
Au jeu CHSH, les stratégies quantiques sont limitées par la borne de Tsirelson, à ~85% de réussite maximale à ce jeu. Mais, les stratégies post-quantiques, formalisées par les boîtes non-locales, peuvent aller jusqu'à 100%. On aimerait donner un critère pour expliquer pourquoi ces boîtes sont invraisemblables dans la Nature, et l'on conjecture que ce critère est la complexité de communication. En effet, on sait déjà que les corrélations quantiques engendrent une complexité de communication non-triviale, et qu'au contraire les boîtes non-locales qui gagnent à CHSH avec ≥ 91% rendent triviale la complexité de communication (2006). Question ouverte : qu'en est-il des autres boîtes non-locales ? Si on arrive à montrer que les autres boîtes non-locales rendent aussi triviale la complexité de communication, alors on aura une explication pour la présence de la borne de Tsirelson : c'est parce que la complexité de communication doit rester non-triviale pour qu'une stratégie soit possible dans la Nature.
Master student, Université de Sherbrooke
Director: Michel Pioro-Ladrière
Organisation de l’instrumentation pour acheminer les signaux de contrôle sans pièces de conditionnement cryogénique, à l’aide de câble spécialement conçu pour la combinaison de signaux à température ambiante
Intégrer l’initialisation des échantillons de qubit de spin sous un appareil qui peut mesurer le courant de fuite ainsi que générer des hautes tensions. Cette instrument servira pour automatiser, réduire le temps d’analyse ainsi que permettre de développer de nouveau algorithme et forme d’onde pour obtenir plus rapidement le régime à un électron.
Master student, Ottawa University
Director: Anne Broadbent
Rigidity for Monogamy-of-Entanglement Games
In a monogamy-of-entanglement (MoE) game, two players who do not communicate try to simultaneously guess a referee's measurement outcome on a shared quantum state they prepared. We study the prototypical example of a game where the referee measures in either the computational or Hadamard basis and informs the players of her choice.
We show that this game satisfies a rigidity property similar to what is known for some nonlocal games. That is, in order to win optimally, the players' strategy must be of a specific form, namely a convex combination of four unentangled optimal strategies generated by the Breidbart state. We extend this to show that strategies that win near-optimally must also be near an optimal state of this form. We also show rigidity for multiple copies of the game played in parallel.
As an application, we construct for the first time a weak string erasure scheme where the security does not rely on limitations on the parties' hardware. Instead, we add a prover, which enables security via the rigidity of this MoE game. Furthermore, we show that this can be used to achieve bit commitment in a model where it is impossible classically.
PhD student, Polytechnique Montréal
Director: Oussama Moutanabbir
Electric-dipole spin resonance for light-holesin direct bandgap germanium quantum well
PhD student, Université de Sherbrooke
Director: Bertrand Reulet
Fluctuation Loops in microwave circuits
Fluctuation loops are average trajectories that can be observed in noise driven out of equilibrium systems. In electronic circuits they can be observed by measuring two voltages and averaging all trajectories between any pair of points in the resulting (V1,V2) space. The trajectories themselves and other related time domain metric allow us to quantify how much a circuit is breaking equilibrium and its application to microwave circuits paves the way for measurements in the quantum regime.
Master student, Université de Sherbrooke
Director: Bertrand Reulet
Subject to be announced
PhD student, McGill University
Director: Bill Coish
Generalized fast quasi-adiabatic population transfer for improved qubit readout, shuttling, and noise mitigation
Population-transfer schemes are commonly used to convert information robustly stored in some quantum system for manipulation and memory into more macroscopic degrees of freedom for measurement. These schemes may include, e.g., spin-to-charge conversion for spins in quantum dots, detuning of charge qubits between a noise-insensitive operating point and a measurement point, spatial shuttling of qubits encoded in spins or ions, and parity-to-charge conversion schemes for qubits based on Majorana zero modes. A common strategy is to use a slow (adiabatic) conversion. However, in an adiabatic scheme, the adiabaticity conditions on the one hand, and accumulation of errors through dephasing, leakage, and energy relaxation processes on the other hand, limit the fidelity that can be achieved. Here, we give explicit fast quasi-adiabatic (fast-QUAD) conversion strategies (pulse shapes) beyond the adiabatic approximation that allow for optimal state conversion. In contrast with many other approaches, here we account for a general source of noise in combination with pulse shaping. Inspired by analytic methods that have been developed for dynamical decoupling theory, we provide a general framework for unique noise mitigation strategies that can be tailored to the system and environment of interest.
Master student, Polytechnique Montréal
Director: Oussama Moutanabbir
Coherent control in Mid-Infrared
GeSn is a silicon-compatible semiconductor of great interest because of the possibility to engineer the bandgap directness and its energy in the mid-infrared, and the potential for designing monolithic photonic and optoelectronic devices. In this work, we exploit the recent developments made in establishing high-quality, direct bandgap GeSn layers, to investigate the optical injection and coherent control of charge and spin currents in this group IV semiconductor. The study of these processes could play a key role in the development of coherent photon-to-spin interfaces, long-sought after for entanglement distribution, and may have innovative applications in biochemical quantum sensing due to the access to the mid-infrared region. To this end, a full zone 30-band k·p model is applied to obtain the band structure of relaxed GeSn. For one- and two-photon absorption, the optical injection of carrier, spin, current, and spin current are calculated in the independent particle approximation. Critical properties such as the two-photon absorption anisotropy and linear-circular dichroism are also extracted. Finally, coherent control with a bichromatic field of frequencies ω and 2ω is investigated. In this case, with the incorporation of Sn in Ge, we find a significant increase of charge current injection at energies close to the band gap, and of spin current injection for a relatively broad range of energies.
PhD student, Unviersité de Sherbrooke
Director: Alexandre Blais
Realistic simulation of the first 17-qubit surface code experiment
The surface code is a prominent candidate for the realization of quantum error correction with superconducting qubits due to its suitable 2D-gridqubit-arrangement and its relatively high error tolerance. To guide efforts in improving the code ability to preserve logical states, it is necessary top erform realistic modeling of the system based on experimentally informative device characteristics such as individual qubit coherence times, cross-Kerr interactions, and gate fidelities. Here, we solve the complete time-evolutionof a 17-qubit device implementing a distance-3 surface code using a Monte Carlo wave function approach. We also implement an effective model that captures all the desired dynamics while significantly reducing the computational requirements. Using this approach, we analyze the expected code performance as a function of experimentally relevant qubit parameters and their non-uniform distribution on the device. We also investigate the optimal parameter improvements needed to enhance logical state preservation and to reach the threshold.
Master student, Université de Sherbrooke
Director: Michel Pioro-Ladrière
Preparation of a cat state in a superconducting circuit
Encoding information into the naturally large Hilbert space of an harmonic oscillator allows complex states of the light to be considered as a logical basisand used for quantum error correction codes [1]. Through mapping the state of a single qubit onto the state of a cavity, we can obtain multiphoton states known as cat states [2,3,4]. Here, we present an implementation of the qubit cavity mapping protocol (qcMAP) [4,5] using a transmon as an ancilla qubit and a coaxial cavity to store the encoded state. With this hardware, we reach a preparation fidelity of 93%, primarily limited by the relaxation and decoherence time of the transmon and the cavity self-Kerr.
[1]W. Cai et. al., Fundam. Res. 1, 50-67(2021)
[2] N. Ofek, A.Petrenkoet.al., Nature 536, 441-445 (2016)
[3] S. Haroche and J-M.Raimond, Exploring the Quantum (2006)
[4] B. Vlastakis et.al.,Science 342, 6158 (2013)
[5] Z. Leghtas et.al., PRA 87, 042315 (2013)
Master student, McGill University
Director: Bill Coish
Jackiw Rebbi Magnons
We theoretically study the elementary excitations of a magnetic topological insulator. These excitations combine aspects of Jackiw-Rebbi bound states and magnon modes. Specifically, we consider the delocalized excitations of a quantum ferromagnet in contact with a 2D Dirac electron system. The local magnetization gaps the electron system, leading to bound states at magnetic domain walls (Jackiw-Rebbi modes). The delocalized (magnon) excitations of this system thus inherit a charge from the delocalized Jackiw-Rebbi bound states. We show that these composite excitations (Jackiw-Rebbi magnons) can be probed experimentally through the characteristic chiral current distribution, and through unique characteristics of the transverse spin susceptibilities.
Master student, NRC - Ottawa
Director: Louis Gaudreau
Coherent driving of a single heavy hole qubit in a GaAs/AlGaAs double quantum dot device
Master student, Université de Sherbrooke
Director: Eva Dupont-Ferrier
Subject to be announced
PhD student, NRC - Ottawa
Director: Louis Gaudreau
Reversible local response of domain wall networks inferroelectric interfaces of marginally twisted WS2 bilayers
Laurent Molino (1), Leena Aggarwal (1), Vladimir Enaldiev (3), Ryan Plumadore (1), Vladimir Falko (2,3,4), Adina Luican-Mayer (1)*
1 Department of Physics, Universityof Ottawa, Ottawa, Canada
2 National Graphene Institute,University of Manchester, Manchester, UK
3 Department of Physics and Astronomy, University of Manchester, Manchester, UK
4 Henry Royce Institute for AdvancedMaterials, University of Manchester, Manchester, UK
Semiconducting ferroelectric materials with low energy polarisation switching offer a platform for next-generation electronics such as ferroelectric field-effect transistors. Ferroelectric domains at symmetry-broken interfaces of transition metal dichalcogenide films provide an opportunity to combine the potential of semiconducting ferroelectrics with the adaptability of two-dimensional material devices. Here, local control of ferroelectric domains in a marginally twistedWS2 bilayer is demonstrated with a scanning tunneling microscope, and their observed reversible evolution understood using a string-like model of the domain wall network. We identify two characteristic regimes of domain evolution: (i) elastic bending of partial screw dislocations separating smaller domains with twin stacking and (ii) formation of perfect screw dislocations by merging pairs of primary domain walls. We also show that the latter act as the seeds for the reversible restoration of the inverted polarisation.
Master student, Université de Sherbrooke
Director: Michel Pioro-Ladrière
Toolbox for fast tuning of spin qubits into the single electron regime
Initializing a spin qubit device into its operating regime is a long and arduous process. Each gate has to be manually tuned to a very precise value in a large gate voltage space and measuring a single stability diagram can take up to an entire day. Thus, tools to automate part of the tuning process and speedup measurements are presented. By combining statistical analysis, machine learning techniques, high performance instrumentation and unconventional measuring techniques, we can optimize the process of finding the single electron regime in a single dot stability diagram while reducing the amount data needed to do so.
Master student, Université de Sherbrooke
Director: Bertrand Reulet
Characterisation of localized defects in hBN: en route to a quantumlight emitting diode (QLED)
hBN, a large-gap van der Waals material, hosts stable, single photon emitters (SPEs) in the visible, making it a promising platform for quantum photonics [1]. The optical properties of the single photon emitters have been the subject of several studies, but their electrical and optoelectronic properties are still largely unexplored. Here, such properties are investigated, with photoluminescence (PL) mapping, spectroscopy (5K to 300K) and lifetime measurements. Preliminary results indicate multiple sharp and localized luminescent defects exhibiting characteristic single photon emitter behaviors. However, defects are highly concentrated on the hBN flakes, generating an intense background emission. Further investigation of defect engineering, reducing the defect density, must be done before getting into time correlated measurements and optoelectronic control, which could pave the way for the development of an electrically pumped single-photon source.
[1]Tran al., Nat. Nanotechnol., 11 (2016).
PhD student, McGill Unversity
Director: Lilian Childress
A Fiber-Based Microcavity Coupled to a Colour Center in Diamond
Color centers in diamond are promising solid-state spin-qubit systems for quantum information thanks to their atom-like spin-optical properties. Two prospective candidates are the nitrogen-vacancy (NV) and germanium-vacancy (GeV). Current implementations with the NV center are restricted by its low emission rate (3%) into its coherent transition and spectral diffusion. In turn, the use of the GeV is limited by its spin-orbit interaction necessitating low-temperature operation. We present our current results in coupling a fiber-based open microcavity (measured finesse of F~8000) to a GeV at ~ 15K. Achieving a reduced lifetime of 3.28+/-0.03 ns (6 ns) and an expected Purcell Enhancement of the zero-phonon line of 11 +/-4.
Master student, McGill University
Director: Kartiek Agarwal
Scars and Fragmented Hamiltonians from Automaton circuits
We provide a systematic approach for constructing approximate quantum many-body scars (QMBS) starting from two-layer Floquet automaton circuits that exhibit trivial many-body revivals. We do so by applying successively more restrictions that force local gates of the automaton circuit to commute concomitantly more accurately when acting on select scar states. With these rules in place, an effective local, Floquet Hamiltonian is seen to capture dynamics of the automata over a long prethermal window, and neglected terms can be used to estimate the relaxationof revivals. We provide numerical evidence for such a picture and use our construction to derive several QMBS models, including the celebrated PXP model.
Michael J Gullans (Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, Maryland 20742 USA)NSERCGrants RGPIN-2019-06465, and DGECR- 2019-00011, Tomlinson Scholar Fund
PhD student, Université de Sherbrooke
Director: Alexandre Blais
Dynamics of Transmon Ionization
Qubit measurement and control in circuit QED rely on microwave drives, with higher drive amplitudes ideally leading to faster processes. However, degradation in qubit coherence time and readout fidelity has been observed even under moderate drive amplitudes corresponding to few photons populating the measurement resonator. Here, we numerically explore the dynamics of a driven transmon-resonator system under strong and nearly resonant measurement drives, and find clear signatures of transmon ionization where the qubit escapes out of its cosine potential. Using a semiclassical model, we interpret this ionization as resulting from resonances occurring at specific resonator photon populations. We find that the photon populations at which these spurious transitions occur are strongly parameter dependent and that they can occur at low resonator photon population, something which may explain the experimentally observed degradation in measurement fidelity.
PhD student, Université de Sherbrooke
Director: Mathieu Juan
An all-fiber solution to single-photon emission and collection
Quantum light sources producing on-demand streams of single photons are an integral part of photonic systems in applications such as linear optical quantum computing and quantum communications. So far, three main approaches for the hybrid integration of single-photon sources (SPSs) offer the necessary flexibility to meet the stringent requirements of most quantum applications, namely wafer-bonding, transfer-printing and the pick-and-place technique. Here, we propose another avenue to fabricate SPSs directly into optical fibers. We present numerical results predicting that such all-fiber SPSs could operate in the weak-coupling regime of waveguide quantum electrodynamics as well as offer high photon collection efficiency. We fabricated and characterized the first microstructured polymer optical fibers (hMOFs) homogeneously doped with colloidal quantum dots (cQDs). However, time-correlated single photon counting measurements found no significant change in the radiative decay rate for this first generation of cQD-overdoped hMOFs.
PhD student, Université de Sherbrooke
Director: Michel Pioro-Ladrière
Subject to be announced
PhD student, Ottawa University
Director: Anne Broadbent
Device-independent Oblivious Transfer from the Bounded-Quantum-Storage-Model and Computational Assumptions
We present a device-independent protocol for oblivious transfer (DIOT) in the bounded-quantum-storage-model, and analyze its security. Our protocol is everlastingly secure and aims to be more practical than previous DIOT protocols, since it does not require non-communication assumptions that are typical from protocols that use Bell inequality violations; instead, the device-independence comes from a recent self-testing protocol which makes use of a post-quantum computational assumption.