May 11, 2017 8:30 AM
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May 11, 2017 4:15 PM
May 11, 2017 8:30 AM
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May 11, 2017 4:15 PM
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Polytechnique Montréal
Polytechnique Montréal
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.
8h30 - 9h00 : Inscription (Hall Lassonde, M-1100)
9h00 - 9h10 : Mots d'ouverture (local M-1510)
9h10 - 10h10 : Edo Waks, University of Maryland (local M-1510)
Quantum nanophotonics: controlling light with a single quantum dot
10h10 - 10h40 : Pause café (Hall Lassonde, M-1100)
10h40 - 11h25 : Glen Evenbly, Université de Sherbrooke (local M-1510)
Tensor networks methods for quantum many-body systems
11h25 - 12h10 : Denis Seletskiy, Polytechnique Montréal (local M-1510)
Quantum Electrodynamics in Space-Time
12h10 - 14h00 : Dîner (Hall Lassonde, M-1100)
14h00 - 14h45 : Stéphane Kéna-Cohen, Polytechnique Montréal (local M-1510)
Quantum optics with light-matter particles
14h45 - 15h15 : Pause café (Hall Lassonde, M-1100)
15h15 - 16h00 : Yves Bérubé-Lauzière, Université de Sherbrooke (local M-1510)
Superpositions of cavity Fock states with active measurement-
based quantum feedback
16h00 -16h10 : Mots de clôture (local M-1510)
University of Maryland
Quantum nanophotonics: controlling light with a single quantum dot
Interactions between light and matter lie at the heart of optical communication and information technology. Nanophotonic devices enhance light-matter interactions by confining photons to small mode volumes, enabling optical information processing at low energies. In the strong coupling regime, these interactions are sufficiently large that a single photon creates a nonlinear response in a single atomic system. Such single-photon nonlinearities are highly desirable for quantum information processing applications where atoms serve as quantum memories and photons act as carriers of quantum information. In this talk I will discuss our effort to develop and coherently control strongly coupled nanophotonic devices using quantum dots coupled to photonic crystals. Quantum dots are semiconductor “artificial atoms” that can act as efficient photon emitters and stable quantum memories. By embedding them in a photonic crystal cavity that spatially confines light to less than a cubic wavelength we can attain the strong coupling regime. This device platform provides a pathway towards compact integrated quantum devices on a semiconductor chip that could serve as basic components of quantum networks and distributed quantum computers. I will discuss our demonstration of a quantum transistor, the fundamental building block for quantum computers and quantum networks, using a single electron spin in a quantum dot. I will then describe a realization of a new cavity QED approach to measure the state of a spin all-optically. This technique enables efficient spin readout even when the spin has a poor cycling transition. Finally, I will discuss our recent effort to extend our results into the telecommunication wavelengths, and to improve the efficiency and scalability of the structure in order to attain integrated multi-dot devices on a single chip.
Université de Sherbrooke
Tensor networks methods for quantum many-body systems
Quantum many-body systems are hard to study because the associated Hilbert space, containing all possible many-body states, grows exponentially in the system size. However, in recent years progress in understanding quantum entanglement has revealed that only a small region of this huge Hilbert space is actually relevant to the study of quantum many-body systems. Tensor network states have been introduced to efficiently describe quantum states in this small, physically relevant region of the many-body Hilbert space. In this talk I will offer an introduction to tensor network methods and their applications towards the study of quantum many-body systems, and discuss some recent progress in the development of tensor networks as models of the AdS/CFT correspondence.
Polytechnique Montréal
Quantum Electrodynamics in Space-Time
One of the greatest achievements of ultrafast science is to enable access to the elementary dynamics of the fundamental degrees of freedom of matter. The ability to trace the temporal evolution of quasiparticles, collective modes and their correlations in the condensed phases has fueled a leap in our understanding of microscopic many-body interactions. Moreover, recently developed methods of sampling the instantaneous electric field amplitude (in the 1 – 150 THz frequency range) provide us with direct information on ultrafast dynamics which is imprinted on the subcycle structure of the probe field and therefore contains the evolution of the complex response function of the studied system.
It can be argued that the next revolution in quantum physics would involve quantum spectroscopy of light and matter fields. I will review our progress toward the development of the building blocks for detection of quantum fields in space-time. First, I will present our results on first direct probing of vacuum fluctuations of the electric field using the technique of electro-optic sampling. Next, I will show how we produce and detect modified quantum states on the example of a strongly-squeezed phase-stable vacuum, exhibiting a time-domain manifestation of the Heisenberg’s uncertainty principle. Finally, I will outline a path toward a time-domain quantum tomography and conclude with a perspective for the emerging themes out of a personal vantage point: from time-resolved quantum spectroscopy to probing evolution of nonclassical fields in dynamic space-time -- the future of subcycle quantum electrodynamics is bright !
Polytechnique Montréal
Quantum optics with light-matter particles
We will describe recent quantum optical experiments with hybrid light-matter particles called polaritons. In the first part of the talk, we will describe the fascinating physics of organic exciton-polaritons, quasiparticles that can form in optical microcavities. We will highlight how they can be used as low-threshold sources of coherent light and describe our recent experiments on polariton condensates, highlighting the spontaneous formation of quasi long-range order and the presence of nonlinear instabilities. Finally, we will show how the nonlinear properties of these quasiparticles allow for the first observation of room-temperature superfluidity. In the second part of the talk, we will describe traditional quantum optical experiments performed on-chip using nanoscale waveguides supporting surface plasmon-polaritons. In particular we will highlight how single quanta of surface plasmons can be generated and studied and finally we will show our results on the quantum interference of individual surface plasmon-polaritons‹a solid-state analog to the Hong-Ou-Mandel experiment.
Université de Sherbrooke
Superpositions of cavity Fock states with active measurement-based quantum feedback
The measurement-based quantum feedback scheme developed and implemented by Haroche and collaborators [Dotsenko et al., Phys. Rev. A 80, 013805 (2009) and Sayrin et al., Nature 477, 73-77 (2011)] to actively prepare and stabilize specific photon number states in cavity quantum electrodynamics (CQED) is a milestone achievement in actively protecting quantum states from decoherence. This feat was achieved by injecting, after each weak dispersive measurement of the cavity state via Rydberg atoms serving as cavity sensors, a low average number classical field (coherent state) to steer the cavity towards the targeted number state. This talk will present the generalization of the theory developed for targeting number states in order to prepare and stabilize desired superpositions of two cavity photon number states. A new distance measure will be introduced to quantify how close a quantum state superposition is to a targeted state and at the same time to more deeply discriminate different states. Results from realistic simulations taking into account decoherence and imperfections in a CQED set-up will be presented. These demonstrate the validity of the generalized theory and points to the experimental feasibility of preparing and stabilizing such superpositions. This is a further step towards the active protection of more complex quantum states than number states. This work, cast in the context of CQED, is also almost readily applicable to circuit QED.
8h30 - 9h00 : Registration (Hall Lassonde, M-1100)
9h00 - 9h10 : Opening remarks (local M-1510)
9h10 - 10h10 : Edo Waks, University of Maryland (local M-1510)
Quantum nanophotonics: controlling light with a single quantum dot
10h10 - 10h40 : Coffee break (Hall Lassonde, M-1100)
10h40 - 11h25 : Glen Evenbly, Université de Sherbrooke (local M-1510)
Tensor networks methods for quantum many-body systems
11h25 - 12h10 : Denis Seletskiy, Polytechnique Montréal (local M-1510)
Quantum Electrodynamics in Space-Time
12h10 - 14h00 : Lunch (Hall Lassonde, M-1100)
14h00 - 14h45 : Stéphane Kéna-Cohen, Polytechnique Montréal (local M-1510)
Quantum optics with light-matter particles
14h45 - 15h15 : Coffee break (Hall Lassonde, M-1100)
15h15 - 16h00 : Yves Bérubé-Lauzière, Université de Sherbrooke (local M-1510)
Superpositions of cavity Fock states with active measurement-
based quantum feedback
16h00 -16h10 : Closing remarks (local M-1510)
University of Maryland
Quantum nanophotonics: controlling light with a single quantum dot
Interactions between light and matter lie at the heart of optical communication and information technology. Nanophotonic devices enhance light-matter interactions by confining photons to small mode volumes, enabling optical information processing at low energies. In the strong coupling regime, these interactions are sufficiently large that a single photon creates a nonlinear response in a single atomic system. Such single-photon nonlinearities are highly desirable for quantum information processing applications where atoms serve as quantum memories and photons act as carriers of quantum information. In this talk I will discuss our effort to develop and coherently control strongly coupled nanophotonic devices using quantum dots coupled to photonic crystals. Quantum dots are semiconductor “artificial atoms” that can act as efficient photon emitters and stable quantum memories. By embedding them in a photonic crystal cavity that spatially confines light to less than a cubic wavelength we can attain the strong coupling regime. This device platform provides a pathway towards compact integrated quantum devices on a semiconductor chip that could serve as basic components of quantum networks and distributed quantum computers. I will discuss our demonstration of a quantum transistor, the fundamental building block for quantum computers and quantum networks, using a single electron spin in a quantum dot. I will then describe a realization of a new cavity QED approach to measure the state of a spin all-optically. This technique enables efficient spin readout even when the spin has a poor cycling transition. Finally, I will discuss our recent effort to extend our results into the telecommunication wavelengths, and to improve the efficiency and scalability of the structure in order to attain integrated multi-dot devices on a single chip.
Université de Sherbrooke
Tensor networks methods for quantum many-body systems
Quantum many-body systems are hard to study because the associated Hilbert space, containing all possible many-body states, grows exponentially in the system size. However, in recent years progress in understanding quantum entanglement has revealed that only a small region of this huge Hilbert space is actually relevant to the study of quantum many-body systems. Tensor network states have been introduced to efficiently describe quantum states in this small, physically relevant region of the many-body Hilbert space. In this talk I will offer an introduction to tensor network methods and their applications towards the study of quantum many-body systems, and discuss some recent progress in the development of tensor networks as models of the AdS/CFT correspondence.
Polytechnique Montréal
Quantum Electrodynamics in Space-Time
One of the greatest achievements of ultrafast science is to enable access to the elementary dynamics of the fundamental degrees of freedom of matter. The ability to trace the temporal evolution of quasiparticles, collective modes and their correlations in the condensed phases has fueled a leap in our understanding of microscopic many-body interactions. Moreover, recently developed methods of sampling the instantaneous electric field amplitude (in the 1 – 150 THz frequency range) provide us with direct information on ultrafast dynamics which is imprinted on the subcycle structure of the probe field and therefore contains the evolution of the complex response function of the studied system.
It can be argued that the next revolution in quantum physics would involve quantum spectroscopy of light and matter fields. I will review our progress toward the development of the building blocks for detection of quantum fields in space-time. First, I will present our results on first direct probing of vacuum fluctuations of the electric field using the technique of electro-optic sampling. Next, I will show how we produce and detect modified quantum states on the example of a strongly-squeezed phase-stable vacuum, exhibiting a time-domain manifestation of the Heisenberg’s uncertainty principle. Finally, I will outline a path toward a time-domain quantum tomography and conclude with a perspective for the emerging themes out of a personal vantage point: from time-resolved quantum spectroscopy to probing evolution of nonclassical fields in dynamic space-time -- the future of subcycle quantum electrodynamics is bright !
Polytechnique Montréal
Quantum optics with light-matter particles
We will describe recent quantum optical experiments with hybrid light-matter particles called polaritons. In the first part of the talk, we will describe the fascinating physics of organic exciton-polaritons, quasiparticles that can form in optical microcavities. We will highlight how they can be used as low-threshold sources of coherent light and describe our recent experiments on polariton condensates, highlighting the spontaneous formation of quasi long-range order and the presence of nonlinear instabilities. Finally, we will show how the nonlinear properties of these quasiparticles allow for the first observation of room-temperature superfluidity. In the second part of the talk, we will describe traditional quantum optical experiments performed on-chip using nanoscale waveguides supporting surface plasmon-polaritons. In particular we will highlight how single quanta of surface plasmons can be generated and studied and finally we will show our results on the quantum interference of individual surface plasmon-polaritons‹a solid-state analog to the Hong-Ou-Mandel experiment.
Université de Sherbrooke
Superpositions of cavity Fock states with active measurement-based quantum feedback
The measurement-based quantum feedback scheme developed and implemented by Haroche and collaborators [Dotsenko et al., Phys. Rev. A 80, 013805 (2009) and Sayrin et al., Nature 477, 73-77 (2011)] to actively prepare and stabilize specific photon number states in cavity quantum electrodynamics (CQED) is a milestone achievement in actively protecting quantum states from decoherence. This feat was achieved by injecting, after each weak dispersive measurement of the cavity state via Rydberg atoms serving as cavity sensors, a low average number classical field (coherent state) to steer the cavity towards the targeted number state. This talk will present the generalization of the theory developed for targeting number states in order to prepare and stabilize desired superpositions of two cavity photon number states. A new distance measure will be introduced to quantify how close a quantum state superposition is to a targeted state and at the same time to more deeply discriminate different states. Results from realistic simulations taking into account decoherence and imperfections in a CQED set-up will be presented. These demonstrate the validity of the generalized theory and points to the experimental feasibility of preparing and stabilizing such superpositions. This is a further step towards the active protection of more complex quantum states than number states. This work, cast in the context of CQED, is also almost readily applicable to circuit QED.