October 12, 2021 1:30 PM
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October 13, 2021 5:00 PM
October 12, 2021 1:30 PM
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October 13, 2021 5:00 PM
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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.
13h25 - 13h30 Mot d'ouverture
13h30 - 14h30 Andrew Potter, University of British Columbia
Simulating highly-entangled matter with quantumtensor networks
14h30 - 14h45 Pause café / discussions sur Remo
14h45 - 15h45 Stephanie Simmons, Simon Fraser University
Silicon Colour Centres
15h45 - 16h45 Compétition d'affiches
13h30 - 14h30 Francesco Borsoi, TUDelft (QuTech)
Quantum information processing with semiconductor technology:
from qubits to integrated quantum circuits
14h30 - 14h:45 Pause café / discussions sur Remo
14h45 - 15h45 Andrew Childs, University of Maryland
Efficient quantum algorithm for dissipative nonlinear
differential equations
15h45 - 16h00 Pause café / discussions sur Remo
16h00 - 17h00 Activité Équité, diversité et inclusion avec Madame Julie Dumontier
Atelier d'écriture épicène
17h00 Mot de clôture (annonce des prix de la compétition d'affiches)
Center for Quantum Information and Computer Science (QuICS)
University of Maryland
Efficient quantum algorithm for dissipative nonlinear differential equations
Nonlinear differentialequations model diverse phenomena but are notoriously difficult to solve. Whilethere has been extensive previous work on efficient quantum algorithms for lineardifferential equations, the linearity of quantum mechanics has limitedanalogous progress for the nonlinear case. Despite this obstacle, we develop aquantum algorithm for dissipative quadratic n-dimensional ordinary differentialequations. Assuming R<1, where R is a parameter characterizing the ratio ofthe nonlinearity and forcing to the linear dissipation, this algorithm hascomplexity T^2 q poly(log T, log n, log(1/ϵ))/ϵ, where T is the evolution time, ϵ is theallowed error, and q measures decay of the solution. This is an exponentialimprovement over the best previous quantum algorithms, whose complexity isexponential in T. While exponential decay precludes efficiency, drivenequations can avoid this issue despite the presence of dissipation. Ouralgorithm uses the method of Carleman linearization, for which we give aconvergence theorem. This method maps a system of nonlinear differentialequations to an infinite-dimensional system of linear differential equations,which we discretize, truncate, and solve using the forward Euler method and thequantum linear system algorithm. We also provide a lower bound on theworst-case complexity of quantum algorithms for general quadratic differentialequations, showing that the problem is intractable for R≥sqrt(2). Finally, wediscuss potential applications, showing that the R<1 condition can besatisfied in realistic epidemiological models and giving numerical evidencethat the method may describe a model of fluid dynamics even for larger valuesof R.
Based on joint work withJin-Peng Liu, Herman Kolden, Hari Krovi, Nuno Loureiro, and KonstantinaTrivisa.
University of British Columbia
Simulating highly-entangled matter with quantumtensor networks
Quantum computation tantalizing promises efficient solutions to a broad range of classically-hard materials and chemistry simulation problems of interest to both basic science and practical applications. However, nascent quantum processors are severely limited in both memory and accuracy, and remain a long way from surpassing state-of-the-art classical computational methods. In this talk, I will review recent progress in bridging this gap by leveraging efficient quantum data compression afforded by tensor network representations, along with opportunistic midcircuit qubit reset and re-use in order to simulate large-scale models of quantum materials with relatively few qubits. I will highlight recent experimental implementations of quantum tensor network algorithms for simulating entangled ground-states and non-equilibrium dynamics of correlated spins and electrons on a trapped ion quantum processor.
Technical University of Delft (QuTech)
Quantum information processing with semiconductor technology: from qubits to integrated quantum circuit
Our approach toward scalable quantum technology departs from the transistor, the most replicated structure made by mankind. We define qubits on the spin states of electrons and holes in silicon and germanium quantum dots. In this talk I will present our recent results in increasing the qubit quality and quantity. First, we show that even a single hole can be coherently controlled and that gate operations can reach fidelities of 99.99%. Through dynamical decoupling we obtain record coherence times for holes and are able to measure the transversal hyperfine interaction with nuclear spins. Second, we demonstrate that quantum dot qubits and control electronics can be operated in the same temperature regime as a stepping stone toward integrated quantum circuits. Third, we construct a 2x2 quantum dot array and obtain universal control and demonstrate coherent execution of a quantum circuit that entangles and disentangles all four qubits. Finally, I will present our strategies to overcome qubit-to-qubit variations, aiming to build quantum systems with fewer control lines than number of qubits, targeting to achieve a quantum advantage with the same materials and techniques that enabled todays information age.
Simon Fraser University
and Photonic Inc.
Silicon Colour Centres
The future global quantum internet will requirehigh-performance matter-photon interfaces. The highly demanding technologicalrequirements indicate that the matter-photon interfaces currently under studyall have potentially unworkable drawbacks, and there is a global race underwayto identify the best possible new alternative. For overwhelming commercial andquantum reasons, silicon is the best possible host for such an interface.Silicon is not only the most developed integrated photonics and electronicsplatform by far, isotopically purified silicon-28 has also set records forquantum lifetimes at both cryogenic and room temperatures [1]. Despite this, thevast majority of research into photon-spin interfaces has notably focused onvisible-wavelength colour centres in other materials. In this talk I willintroduce a variety of silicon colour centres and discuss their properties inisotopically purified silicon-28. Some of these centres have zero-phononoptical transitions in the telecommunications bands [2], some have long-livedspins in their ground states [3], and some, including the newly rediscovered Tcentre, have both [4].
[1] K. Saeedi, S.Simmons, J.Z. Salvail, et al. Science 342:830 (2013).
[2] C. Chartrand, L. Bergeron, K.J. Morse, et al. Phys. Rev. B 98:195201(2018).
[3] K. Morse, R. Abraham, A. DeAbreu, et al. Science Advances 3:e1700930(2017).
[4] L. Bergeron, C. Chartrand, A.T.K. Kurkjian, et al. PRXQuantum 1 020301(2020).
L’atelier en français couvrira les thèmes :
- Pourquoi l'écriture épicène est nécessaire ?
- Quels sont les grands principes de l'épicène ?
- Comment l'appliquer dans vos écrits ?
Julie a effectué des études de premier et deuxième cycles en sciences sociales et en langues à l'Université Laval, la Universidad de Granada, Universität Passau et l'Institut d'études politiques de Bordeaux. Elle a ensuite poursuivi des études de premier et deuxième cycle en droit à l'Université du Québec à Montréal. Avec plus de 15 ans d’expérience dans le domaine des droits humains, avec une spécialisation en droits des femmes, et plus de 10 ans d’expérience en formation, Julie croit fermement à l’utilité d’offrir des services présentant une autre vision du monde.
Étudiant au doctorat, Poytechnique Montréal
Directeur: Oussama Moutanabbir
Light Hole Quantum Well on Silicon (Table #1)
Si-compatible low-dimensional systems have been exploiting either tensile strained Si or compressively strained Germanium (Ge) quantum wells (QWs). For quantum information, the latter has been explored in new schemes for hole spin qubits. Hole spins have attracted a great deal of attention. Nevertheless, most of experimental investigations on 2D gas systems have so far focused on heavy-hole states (HH) due to the compressively strained heterostructure currently exploited, where the valence band degeneracy is lifted and leaves HH states energetically above the light-hole (LH) states. However, the ability to exploit LH states will be a powerful paradigm beneficial for quantum information technologies. To harness these largely unexplored advantages of LH states, we present a new low-dimensional system consisting of highly tensile strained Ge quantum well grown on Si wafers using GeSn as barriers. Several spectroscopic techniques were used to identify the LH confined states in the Ge well. The obtained heterostructure shows optical transitions that are modulated in the midinfrared range. This ability to engineer quantum structure where LH is the ground state in an optically active group IV platform lays the groundwork for a new class of Si-compatible quantum technologies.
Étudiant à la maîtrise, Université McGill
Directeur: Kartiek Agarwal
Reducing Decoherence in Majorana Fermions via Periodic Driving (Table #2)
Realistic realizations of Majorana fermions used for quantum computing are affected by noise induced decoherence. We propose a protocol to reduce those effects. This protocol relies on rapidly exchanging the parity of the Majoranas effectivelly flipping the relative phase for a qubit state. This is done physically by periodically modulating the coupling between a quantum dot and the quantum wire hosting the Majoranas creating a Landau-Zener transition between the wire and the dot. Effectivelly, the protocol acts as a spin echo sequence effectivelly removing low frequency noise being an ideal candidate for 1/f noise effects.
Étudiant à la maîtrise, Université McGill
Directeur: Kartiek Agarwal
Hybridization and Conductance of Floquet Majorana (Table #3)
It is an ongoing challenge to engineer setups where Majorana zero modes at the ends of one-dimensional topological superconductors are well isolated which is the essence of topological protection. Recent developments have indicated that periodic driving of a system can dynamically induce symmetries that its static counterpart does not possess [1]. We further develop the original protocol [2] where this idea [1] is applied to a system of a quantum dot (QD) coupled to a Kitaev chain hosting imperfect (overlapping) Majoranas. We numerically simulate a dynamical protocol in which an electron hops back and forth from the QD and the chain by Landau-Zener transition driven via time periodic local potential on the QD. We demonstrate that the current protocol reduces a non-zero hybridization energy that manifests from imperfect Majoranas by orders of magnitude. Furthermore, by numerically computing conductance of these driven Floquet Majorana, we show that the conductance peaks are shifted towards zero energy.
[1] K. Agarwal and I. Martin, Phys. Rev. Lett. 125, 080602 (2020)
[2] I. Martin and K. Agarwal, PRX Quantum 1, 020324 (2020)
Étudiant au doctorat, Université de Sherbrooke
Directrice: Éva Dupont-Ferrier
All-silicon double quantum dot architecture for spin qubit (Table #4)
Silicon spin qubits, with their long coherence time [1] and compatibility with industrial CMOS technology [2-3], hold great promise for large-scale quantum computing. Nevertheless, improvements in device reproducibility and fabrication are still needed to build a scalable spin qubit architecture. Leveraging CMOS industry's fabrication expertise, we present here a silicon double quantum dot architecture for a spin qubit fully fabricated in a 300 mm integrated process at the IMEC manufacturing facility. On these devices, we demonstrate reproducible single and double quantum dots operation with tunable inter-dot coupling. Using integrated SET as a charge sensor we show single-shot charge readout and measure a tunneling rate controllable over a decade.These results pave the way for the use of silicon spin qubits for large-scale quantum computing.
Étudiant au doctorat, Université McGill
Directeur: Bill Coish
Generalizedfast quasi-adiabatic population transfer: Improvedqubit readout, shuttling, and noise mitigation (Table #5)
Master student, Polytechnique Montréal
Director: Oussama Moutanabbir
Optical injection of spin current in GeSn (Table #7)
Recent progress in the development of direct band gap GeSn is exploited to investigate the optical injection and coherent control of spin currents in this group IV semiconductor. The analysis of these properties could provide essential information for future innovative optical photon-to-spin conversion interfaces, long-sought after for entanglement distribution. A 30-band k•p model is used to evaluate the electronic properties in the material for a relatively wide range of energies, and a linear tetrahedron method is employed for the Brillouin zone integrations. Carrier, spin, current, and spin current injection rates are calculated for a bichromatic field of frequencies ω and 2ω.
Étudiant à la maîtrise, Université McGill
Directeur: Bill Coish
Toward an understanding of the interplay between quantum magnetism and electron transport in magnetic topological insulators (Table #8)
TMotivated by magnetotransport experiments on magnetic topological insulators, a theoretical study of surface Dirac cone electrons coupled to magnetic moments has been done [1]. That work showed that the electronic response is determined by the magnetic configuration - the electronic spectrum is gapped in a region of ferromagnetically ordered moments, but the gap vanishes at domain walls. This vanishing gap gives rise to one-dimensional channels of conductance. Taking the interplay between Dirac electrons and magnetic moments further, we wish to study a coupled system where the magnetic moments are treated quantum mechanically. A quantum-mechanical treatment may provide a more complete understanding of the role that the domain-wall bound states play in the behaviour of the magnetoconductance in magnetic topological insulators and in heterostructures. For example, domain walls may be delocalized due to quantum fluctuations while still coupling to the Dirac fermions. The generalization of the classical model to the quantum regime could help in the development of spintronics applications and sensors of magnetic excitations.
[1] K. L. Tiwari, W. A. Coish, and T. Pereg-Barnea Phys. Rev. B 96, 235120 (2017).
Étudiant au doctorat, Université de Sherbrooke
Directrice: Éva Dupont-Ferrier
Implementation and characterization of a radio-frequency reflectometry setup for charge detection in a CMOS device (Table #8)
Spin qubits in silicon are great candidates for scalable quantum information processors due to their long coherence time combined with compatibility with industrial CMOS fabrication lines [1]. The spin-readout is obtained by spin-to-charge conversion using a nearby SET. This requires multiple additional leads and limits the scalability of the system. RF-reflectometry measurement provides a compact alternative [2,3] as only one lead is necessary to control and read the qubit [4]. The critical part for this measurement is to obtain an impedance matching, at low temperature, between the resonant circuit and the RF-line. This is due to the temperature dependence of each of the tank circuit components and the sample-to-sample capacitance variability. In this poster, we present the setup and characterization of a reflectometry setup as well as charge sensing measurements performed on a nanoscale CMOS transistor. Then we show the use of tunable capacitors to target high sensitivity RF-measurement for spin qubit readout.
[1] M. Veldhorst, et al., Nat. Nano. 9, 981–985 (2014)
[2] B. J. Villis, et al., Appl. Phys. Lett. 104, 233503 (2014)
[3] I. Ahmed, et al., Appl. Phys. Lett. 10, 014018 (2018)
[4] P. Pakkiam, et al., Phys. Rev., 8, 041032 (2018)
Étudiant au doctorat, Université de Sherbrooke
Directeur: Michel Pioro-Ladrière
Fast andmodular measurement platform for quantum dots tuning into the spin qubit regime (Table #9)
Spin qubits are a promising architecture forquantum computers thanks to their long coherence time and compatibility withindustrial fabrication techniques. However, qubits characterization andinitialization in a desired configuration is a time-consuming process. Suchchallenges are slowing down progress in this field of research, especially whenstudying multi-qubit systems. To address those problems, a fast and modularmeasurement platform for spin qubits, using Field Programmable Gate Arrays(FPGAs), is presented. We also introduce a “Park and Fly” technique,implemented on this platform, to measure the stability diagram of quantum dots.By doing so, it is possible to achieve high voltage amplitudes with highresolution by combining DC and AC signals. A “Park” DC signal is set to measurea specific part of a stability diagram while a “Fly” AC signal is allowing highresolution sweeping in the region around the “Park” signal. As a proof ofconcept, this technique is tested on a quantum dot simulator implementeddirectly inside an FPGA. By combining this approach with the modularity of theplatform, efficient and simultaneous characterization of multiple qubit devicesis feasible.
Postdoc, Ottawa University
Directrice : Anne Broadbent
Neither contextuality nor non-locality admits catalysts (Table #10)
We discuss arXiv:2102.07637, in which we show that the resource theory of contextuality does not admit catalysts. As a corollary, we observe that the same holds for non-locality. This adds a further example to the list of "anomalies of entanglement", showing that non-locality and entanglement behave differently as resources. We also show that catalysis remains impossible even if instead of classical randomness we allow some more powerful behaviors to be used freely in the free transformations of the resource theory.
Étudiant au doctorat, Polytechnique Montréal
Directeur: Oussama Moutanabbir
Hole spins in germanium quantum wells (Table #11)
Hole spins in low dimensional systems have attracted significant attention during the past few years because of the complexity of their spin behavior. They are also promising candidates as building blocks for quantum technologies since they have a weak hyperfine interaction with surrounding nuclei and can be manipulated efficiently with electric fields. The inherently large spin-orbit coupling in germanium (Ge) is an essential ingredient to many interesting hole spin phenomena. We present herein a few interesting hole spin phenomena and properties in germanium quantum wells : 1) the vanishing Zeeman energy of a heavy-hole gas in compressively strained Ge quantum well, and 2) the experimental realisation and overview of the spin properties of a two-dimensional light-hole gas in tensile strained Ge quantum well.
Étudiant à la maîtrise, Université McGill
Director: Kartiek Agarwal
Applications and dynamical properties of quantum circuits based oncellular automatons (Table #12)
Quantum circuits are at the heart of quantum computing and quantum error correction. Understanding their dynamical properties is therefore of fundamental importance for the development of quantum computers. By focusing on a simpler class of quantum circuits based on cellular automatons, one can use analytical methods to study the quantum properties of the corresponding chain of qubits. Possible applications of this special class of circuits include reducing the hardware required for quantum error correction and better understanding of fragmentation, a process that occurs in some Hamiltonian systems with dynamical constraints and leads to a breakdown of the energy thermalization hypothesis.
Professionnel, Polytechnique Montréal
Directeur: Oussama Moutanabbir
Connecting atomic structure and quantum properties (Table #13)
Here we will present a framework to connect atomic scale material characterization of spin quantum bit structures from Atom Probe Tomography via tight binding simulations to relevant quantum transport properties. In particular we will explore the origin of variations in valley splitting in strained, isotopically pure 28 Silicon quantum wells.
Étudiant au doctorat, Université de Sherbrooke
Directeur: Bertrand Reulet
Statistics of Broadband Microwave Photons (Table #14)
Choosing the right first-quantization basis is critical to interpret correctly experimental statistics. In this paper we suggest two simple bicolor photon operators as candidates for a general wideband photon operator. Through wideband (\Delta f/f \sim 0.5) voltage measurements in the microwave domain, we infer the statistics of both candidates and show that the proper choice of operator leads to the same thermal statistics as the usual narrowband photon operator.
Étudiante au doctorat, Université McGill
Directeur: Bill Coish
Transient spectroscopy in cavity QED (Table #15)
13:25 - 13:30 Opening remarks
13:30 - 14:30 Andrew Potter, University of British Columbia
Simulating highly-entangled matter with quantumtensor networks
14:30 - 14:45 Coffee break / discussions on Remo
14:45 - 15:45 Stephanie Simmons, Simon Fraser University
Silicon Colour Centres
15:45 - 16:45 Poster competition on Remo
13:30 - 14:30 Francesco Borsoi, TUDelft (QuTech)
Quantum information processing with semiconductor technology:
from qubits to integrated quantum circuits
14:30 - 14:45 Coffee break / discussion on Remo
14:45 - 15:45 Andrew Childs, University of Maryland
Efficient quantum algorithm for dissipative nonlinear
differential equations
15:45 - 16:00 Coffee break / discussions on Remo
16:00 - 17:00 Equity, diversity and inclusion with Madame Julie Dumontier
Atelier d'écriture épicène (French language)
17:00 Closing remarks (announce prizes for posters)
Center for Quantum Information and Computer Science (QuICS)
University of Maryland
Efficient quantum algorithm for dissipative nonlinear differential equations
Nonlinear differentialequations model diverse phenomena but are notoriously difficult to solve. Whilethere has been extensive previous work on efficient quantum algorithms for lineardifferential equations, the linearity of quantum mechanics has limitedanalogous progress for the nonlinear case. Despite this obstacle, we develop aquantum algorithm for dissipative quadratic n-dimensional ordinary differentialequations. Assuming R<1, where R is a parameter characterizing the ratio ofthe nonlinearity and forcing to the linear dissipation, this algorithm hascomplexity T^2 q poly(log T, log n, log(1/ϵ))/ϵ, where T is the evolution time, ϵ is theallowed error, and q measures decay of the solution. This is an exponentialimprovement over the best previous quantum algorithms, whose complexity isexponential in T. While exponential decay precludes efficiency, drivenequations can avoid this issue despite the presence of dissipation. Ouralgorithm uses the method of Carleman linearization, for which we give aconvergence theorem. This method maps a system of nonlinear differentialequations to an infinite-dimensional system of linear differential equations,which we discretize, truncate, and solve using the forward Euler method and thequantum linear system algorithm. We also provide a lower bound on theworst-case complexity of quantum algorithms for general quadratic differentialequations, showing that the problem is intractable for R≥sqrt(2). Finally, wediscuss potential applications, showing that the R<1 condition can besatisfied in realistic epidemiological models and giving numerical evidencethat the method may describe a model of fluid dynamics even for larger valuesof R.
Based on joint work withJin-Peng Liu, Herman Kolden, Hari Krovi, Nuno Loureiro, and KonstantinaTrivisa.
University of British Columbia
Simulating highly-entangled matter with quantumtensor networks
Quantum computation tantalizing promises efficient solutions to a broad range of classically-hard materials and chemistry simulation problems of interest to both basic science and practical applications. However, nascent quantum processors are severely limited in both memory and accuracy, and remain a long way from surpassing state-of-the-art classical computational methods. In this talk, I will review recent progress in bridging this gap by leveraging efficient quantum data compression afforded by tensor network representations, along with opportunistic midcircuit qubit reset and re-use in order to simulate large-scale models of quantum materials with relatively few qubits. I will highlight recent experimental implementations of quantum tensor network algorithms for simulating entangled ground-states and non-equilibrium dynamics of correlated spins and electrons on a trapped ion quantum processor.
Technical University of Delft (QuTech)
Quantum information processing with semiconductor technology: from qubits to integrated quantum circuit
Our approach toward scalable quantum technology departs from the transistor, the most replicated structure made by mankind. We define qubits on the spin states of electrons and holes in silicon and germanium quantum dots. In this talk I will present our recent results in increasing the qubit quality and quantity. First, we show that even a single hole can be coherently controlled and that gate operations can reach fidelities of 99.99%. Through dynamical decoupling we obtain record coherence times for holes and are able to measure the transversal hyperfine interaction with nuclear spins. Second, we demonstrate that quantum dot qubits and control electronics can be operated in the same temperature regime as a stepping stone toward integrated quantum circuits. Third, we construct a 2x2 quantum dot array and obtain universal control and demonstrate coherent execution of a quantum circuit that entangles and disentangles all four qubits. Finally, I will present our strategies to overcome qubit-to-qubit variations, aiming to build quantum systems with fewer control lines than number of qubits, targeting to achieve a quantum advantage with the same materials and techniques that enabled todays information age.
Simon Fraser University
and Photonic Inc.
Silicon Colour Centres
The future global quantum internet will requirehigh-performance matter-photon interfaces. The highly demanding technologicalrequirements indicate that the matter-photon interfaces currently under studyall have potentially unworkable drawbacks, and there is a global race underwayto identify the best possible new alternative. For overwhelming commercial andquantum reasons, silicon is the best possible host for such an interface.Silicon is not only the most developed integrated photonics and electronicsplatform by far, isotopically purified silicon-28 has also set records forquantum lifetimes at both cryogenic and room temperatures [1]. Despite this, thevast majority of research into photon-spin interfaces has notably focused onvisible-wavelength colour centres in other materials. In this talk I willintroduce a variety of silicon colour centres and discuss their properties inisotopically purified silicon-28. Some of these centres have zero-phononoptical transitions in the telecommunications bands [2], some have long-livedspins in their ground states [3], and some, including the newly rediscovered Tcentre, have both [4].
[1] K. Saeedi, S.Simmons, J.Z. Salvail, et al. Science 342:830 (2013).
[2] C. Chartrand, L. Bergeron, K.J. Morse, et al. Phys. Rev. B 98:195201(2018).
[3] K. Morse, R. Abraham, A. DeAbreu, et al. Science Advances 3:e1700930(2017).
[4] L. Bergeron, C. Chartrand, A.T.K. Kurkjian, et al. PRXQuantum 1 020301(2020).
The workshop (French language) will be about :
- Pourquoi l'écriture épicène est nécessaire ?
- Quels sont les grands principes de l'épicène ?
- Comment l'appliquer dans vos écrits ?
Julie a effectué des études de premier et deuxième cycles en sciences sociales et en langues à l'Université Laval, la Universidad de Granada, Universität Passau et l'Institut d'études politiques de Bordeaux. Elle a ensuite poursuivi des études de premier et deuxième cycle en droit à l'Université du Québec à Montréal. Avec plus de 15 ans d’expérience dans le domaine des droits humains, avec une spécialisation en droits des femmes, et plus de 10 ans d’expérience en formation, Julie croit fermement à l’utilité d’offrir des services présentant une autre vision du monde.
Ph.D. student, Poytechnique Montréal
Director: Oussama Moutanabbir
Light Hole Quantum Well on Silicon (Table #1)
Si-compatible low-dimensional systems have been exploiting either tensile strained Si or compressively strained Germanium (Ge) quantum wells (QWs). For quantum information, the latter has been explored in new schemes for hole spin qubits. Hole spins have attracted a great deal of attention. Nevertheless, most of experimental investigations on 2D gas systems have so far focused on heavy-hole states (HH) due to the compressively strained heterostructure currently exploited, where the valence band degeneracy is lifted and leaves HH states energetically above the light-hole (LH) states. However, the ability to exploit LH states will be a powerful paradigm beneficial for quantum information technologies. To harness these largely unexplored advantages of LH states, we present a new low-dimensional system consisting of highly tensile strained Ge quantum well grown on Si wafers using GeSn as barriers. Several spectroscopic techniques were used to identify the LH confined states in the Ge well. The obtained heterostructure shows optical transitions that are modulated in the midinfrared range. This ability to engineer quantum structure where LH is the ground state in an optically active group IV platform lays the groundwork for a new class of Si-compatible quantum technologies.
Master student, McGill University
Director: Kartiek Agarwal
Reducing Decoherence in Majorana Fermions via Periodic Driving (Table #2)
Realistic realizations of Majorana fermions used for quantum computing are affected by noise induced decoherence. We propose a protocol to reduce those effects. This protocol relies on rapidly exchanging the parity of the Majoranas effectivelly flipping the relative phase for a qubit state. This is done physically by periodically modulating the coupling between a quantum dot and the quantum wire hosting the Majoranas creating a Landau-Zener transition between the wire and the dot. Effectivelly, the protocol acts as a spin echo sequence effectivelly removing low frequency noise being an ideal candidate for 1/f noise effects.
Master student, McGill University
Director: Kartiek Agarwal
Hybridization and Conductance of Floquet Majorana (Table #3)
It is an ongoing challenge to engineer setups where Majorana zero modes at the ends of one-dimensional topological superconductors are well isolated which is the essence of topological protection. Recent developments have indicated that periodic driving of a system can dynamically induce symmetries that its static counterpart does not possess [1]. We further develop the original protocol [2] where this idea [1] is applied to a system of a quantum dot (QD) coupled to a Kitaev chain hosting imperfect (overlapping) Majoranas. We numerically simulate a dynamical protocol in which an electron hops back and forth from the QD and the chain by Landau-Zener transition driven via time periodic local potential on the QD. We demonstrate that the current protocol reduces a non-zero hybridization energy that manifests from imperfect Majoranas by orders of magnitude. Furthermore, by numerically computing conductance of these driven Floquet Majorana, we show that the conductance peaks are shifted towards zero energy.
[1] K. Agarwal and I. Martin, Phys. Rev. Lett. 125, 080602 (2020)
[2] I. Martin and K. Agarwal, PRX Quantum 1, 020324 (2020)
Ph.D. student, Université de Sherbrooke
Director: Éva Dupont-Ferrier
All-silicon double quantum dot architecture for spin qubit (Table #4)
Silicon spin qubits, with their long coherence time [1] and compatibility with industrial CMOS technology [2-3], hold great promise for large-scale quantum computing. Nevertheless, improvements in device reproducibility and fabrication are still needed to build a scalable spin qubit architecture. Leveraging CMOS industry's fabrication expertise, we present here a silicon double quantum dot architecture for a spin qubit fully fabricated in a 300 mm integrated process at the IMEC manufacturing facility. On these devices, we demonstrate reproducible single and double quantum dots operation with tunable inter-dot coupling. Using integrated SET as a charge sensor we show single-shot charge readout and measure a tunneling rate controllable over a decade.These results pave the way for the use of silicon spin qubits for large-scale quantum computing.
Ph.D. student, McGill Unversity
Director: Bill Coish
Generalizedfast quasi-adiabatic population transfer: Improvedqubit readout, shuttling, and noise mitigation (Table #5)
Master student, Polytechnique Montréal
Director: Oussama Moutanabbir
Optical injection of spin current in GeSn (Table #6)
Recent progress in the development of direct band gap GeSn is exploited to investigate the optical injection and coherent control of spin currents in this group IV semiconductor. The analysis of these properties could provide essential information for future innovative optical photon-to-spin conversion interfaces, long-sought after for entanglement distribution. A 30-band k•p model is used to evaluate the electronic properties in the material for a relatively wide range of energies, and a linear tetrahedron method is employed for the Brillouin zone integrations. Carrier, spin, current, and spin current injection rates are calculated for a bichromatic field of frequencies ω and 2ω.
Master student, McGill University
Director: Bill Coish
Toward an understanding of the interplay between quantum magnetism and electron transport in magnetic topological insulators (Table #7)
TMotivated by magnetotransport experiments on magnetic topological insulators, a theoretical study of surface Dirac cone electrons coupled to magnetic moments has been done [1]. That work showed that the electronic response is determined by the magnetic configuration - the electronic spectrum is gapped in a region of ferromagnetically ordered moments, but the gap vanishes at domain walls. This vanishing gap gives rise to one-dimensional channels of conductance. Taking the interplay between Dirac electrons and magnetic moments further, we wish to study a coupled system where the magnetic moments are treated quantum mechanically. A quantum-mechanical treatment may provide a more complete understanding of the role that the domain-wall bound states play in the behaviour of the magnetoconductance in magnetic topological insulators and in heterostructures. For example, domain walls may be delocalized due to quantum fluctuations while still coupling to the Dirac fermions. The generalization of the classical model to the quantum regime could help in the development of spintronics applications and sensors of magnetic excitations.
[1] K. L. Tiwari, W. A. Coish, and T. Pereg-Barnea Phys. Rev. B 96, 235120 (2017).
Étudiant au doctorat, Université de Sherbrooke
Directrice: Éva Dupont-Ferrier
Implementation and characterization of a radio-frequency reflectometry setup for charge detection in a CMOS device (Table #8)
Spin qubits in silicon are great candidates for scalable quantum information processors due to their long coherence time combined with compatibility with industrial CMOS fabrication lines [1]. The spin-readout is obtained by spin-to-charge conversion using a nearby SET. This requires multiple additional leads and limits the scalability of the system. RF-reflectometry measurement provides a compact alternative [2,3] as only one lead is necessary to control and read the qubit [4]. The critical part for this measurement is to obtain an impedance matching, at low temperature, between the resonant circuit and the RF-line. This is due to the temperature dependence of each of the tank circuit components and the sample-to-sample capacitance variability. In this poster, we present the setup and characterization of a reflectometry setup as well as charge sensing measurements performed on a nanoscale CMOS transistor. Then we show the use of tunable capacitors to target high sensitivity RF-measurement for spin qubit readout.
[1] M. Veldhorst, et al., Nat. Nano. 9, 981–985 (2014)
[2] B. J. Villis, et al., Appl. Phys. Lett. 104, 233503 (2014)
[3] I. Ahmed, et al., Appl. Phys. Lett. 10, 014018 (2018)
[4] P. Pakkiam, et al., Phys. Rev., 8, 041032 (2018)
Ph.D. student, Université de Sherbrooke
Director: Michel Pioro-Ladrière
Fast andmodular measurement platform for quantum dots tuning into the spin qubit regime (Table #9)
Spin qubits are a promising architecture forquantum computers thanks to their long coherence time and compatibility withindustrial fabrication techniques. However, qubits characterization andinitialization in a desired configuration is a time-consuming process. Suchchallenges are slowing down progress in this field of research, especially whenstudying multi-qubit systems. To address those problems, a fast and modularmeasurement platform for spin qubits, using Field Programmable Gate Arrays(FPGAs), is presented. We also introduce a “Park and Fly” technique,implemented on this platform, to measure the stability diagram of quantum dots.By doing so, it is possible to achieve high voltage amplitudes with highresolution by combining DC and AC signals. A “Park” DC signal is set to measurea specific part of a stability diagram while a “Fly” AC signal is allowing highresolution sweeping in the region around the “Park” signal. As a proof ofconcept, this technique is tested on a quantum dot simulator implementeddirectly inside an FPGA. By combining this approach with the modularity of theplatform, efficient and simultaneous characterization of multiple qubit devicesis feasible.
Postdoc, Ottawa University
Director : Pr Anne Broadbent
Neither contextuality nor non-locality admits catalysts (Table #10)
We discuss arXiv:2102.07637, in which we show that the resource theory of contextuality does not admit catalysts. As a corollary, we observe that the same holds for non-locality. This adds a further example to the list of "anomalies of entanglement", showing that non-locality and entanglement behave differently as resources. We also show that catalysis remains impossible even if instead of classical randomness we allow some more powerful behaviors to be used freely in the free transformations of the resource theory.
Ph.D. student, Polytechnique Montréal
Director: Oussama Moutanabbir
Hole spins in germanium quantum wells (Table #11)
Hole spins in low dimensional systems have attracted significant attention during the past few years because of the complexity of their spin behavior. They are also promising candidates as building blocks for quantum technologies since they have a weak hyperfine interaction with surrounding nuclei and can be manipulated efficiently with electric fields. The inherently large spin-orbit coupling in germanium (Ge) is an essential ingredient to many interesting hole spin phenomena. We present herein a few interesting hole spin phenomena and properties in germanium quantum wells : 1) the vanishing Zeeman energy of a heavy-hole gas in compressively strained Ge quantum well, and 2) the experimental realisation and overview of the spin properties of a two-dimensional light-hole gas in tensile strained Ge quantum well.
Master student, McGill University
Director: Kartiek Agarwal
Applications and dynamical properties of quantum circuits based oncellular automatons (Table #12)
Quantum circuits are at the heart of quantum computing and quantum error correction. Understanding their dynamical properties is therefore of fundamental importance for the development of quantum computers. By focusing on a simpler class of quantum circuits based on cellular automatons, one can use analytical methods to study the quantum properties of the corresponding chain of qubits. Possible applications of this special class of circuits include reducing the hardware required for quantum error correction and better understanding of fragmentation, a process that occurs in some Hamiltonian systems with dynamical constraints and leads to a breakdown of the energy thermalization hypothesis.
Professional, Polytechnique Montréal
Director: Oussama Moutanabbir
Connecting atomic structure and quantum properties (Table #13)
Here we will present a framework to connect atomic scale material characterization of spin quantum bit structures from Atom Probe Tomography via tight binding simulations to relevant quantum transport properties. In particular we will explore the origin of variations in valley splitting in strained, isotopically pure 28 Silicon quantum wells.
Ph.D student, Université de Sherbrooke
Director: Bertrand Reulet
Statistics of Broadband Microwave Photons (Table #14)
Choosing the right first-quantization basis is critical to interpret correctly experimental statistics. In this paper we suggest two simple bicolor photon operators as candidates for a general wideband photon operator. Through wideband (\Delta f/f \sim 0.5) voltage measurements in the microwave domain, we infer the statistics of both candidates and show that the proper choice of operator leads to the same thermal statistics as the usual narrowband photon operator.
Ph.D. student, McGill University
Director: Bill Coish
Transient spectroscopy in cavity QED (Table #15)