November 9, 2017 10:30 AM

November 10, 2017 3:00 PM
November 9, 2017 10:30 AM

November 10, 2017 3:00 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
LouisPhilippe 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 PeregBarnea, McGill University
Dynamic topology  quantized conductance and Majoranas on wires
Professor Philippe StJean, Université de Montréal
Topological physics with light and matter: new horizons
Break
Louis Gaudreau, National Research Council Canada (Ottawa)
Entanglement distribution via coherent photontospin conversion in semiconductor quantum dot circuits
Philippe Lamontagne, National Research Council Canada (Montréal)
BlackBox Impossibility in the Common Reference Quantum State Model
Olivier GagnonGordillo, Québec quantique lead
Presentation of the Québec Quantum ecosystem
Institut quantique  Université de Sherbrooke
Classical and quantum computations as tensor networks
Tensor networks are multilinearalgebra data structures that are finding application in diverse fields of science, from quantum manybody 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 nonlinear 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 sideband cooling. In general, linear cavities are favoured to allow for large photon number providing stronger cooling. I will show that, surprisingly, nonlinear 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 outofequilibrium 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 timeperiodic 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 faulttolerant quantum computation[i]. In the late 2000s, Duncan Haldane (colaureate 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 solidstate, leading to the emergence of a blooming field called topological photonics[iii].
In this presentation, I will describe recent experimental works based on excitonpolaritons, a hybrid lightmatter 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 welldefined topological properties in lattices of coupled microcavities and makes them inherently nonhermitian; on the other hand, their matter part gives rise to a strong Kerrlike 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 solidstate. I will conclude this presentation by discussing how topological protection can provide a powerful asset for generating and stabilizing manybody 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 manybody 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. StJean et al. Opt. Mat. Express 11, 1119 (2021)
[v] I. Carusotto and C. Ciuti. Rev. Mod. Phys. 85, 299 (2013)
[vi] P. StJean 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 photontospin 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 timebin encoded photonic qubits to electron spin qubits and will describe adaptations to employ heavy holes which have a number of attractive properties including gfactor 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 cosupervision 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 exchangeonly 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 lightmatter 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 nanooptoelectronics group with Frank Koppens where he was awarded the prestigious MarieCurie 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)
BlackBox 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 wellknown Common Reference String (CRS) model but appears to be more powerful. In the twoparty setting, a CRQS can sometimes exhibit properties associated with a Random Oracle queried once. We formalize this notion as a Weak OneTime 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 blackbox 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 FiatShamir transform whose security can be blackbox 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 blackbox reduced to a cryptographic game assumption.
Senior Product Manager
Aspen Technology
Biography
Montrealbased quantum physicist, senior product manager, and full stack developer with strong experience building awardwinning 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 MachineToMachine 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.
10h30  10h55 Inscription
10h55  11h00 Mots d'ouverture (Salon A)
11h00  12h00 Gina Passante, California State University, Fullerton (Salon A)
Research as a guide to improve the teaching and
learning of quantum mechanics
12h00  13h30 Dîner (Salle 4 canards)
13h30 14h30 David Poulin, Université de Sherbrooke (Salon A)
Everything you always wanted to know about theoretical
quantum information but were afraid to ask
14h30  15h00 Pause café (Salon B)
15h00 15h30 Edouard Pinsolle, Université de Sherbrooke (Salon A)
Third Moment of Current Fluctuations in a Diffusive Conductor
15h30  16h00 Jean Olivier Simoneau, Université de Sherbrooke (Salon A)
Photon statistics of a Josephson parametric amplifier
from continuous microwave measurements
16h00  16h30 Agustin Di Paolo, Université de Sherbrooke (Salon A)
Quantum technology efforts across the globe:
leveraging its nearterm impact
16h30  18h30 Session d'affiches et rafraîchissement (Salon B)
19h00  Souper INTRIQ dinner (Salle 4 canards)
9h15  10h00 Peter Grüter, Professor at McGill University (Salon A)
Attosecond time resolution by AFM
10h00  10h30 Baptiste Royer, Doctorant at Université de Sherbrooke (Salon A)
Itinerant microwave photon detector
10h30  11h00 Pause café (Salon B)
11h00  12h00 Michael Hilke, Professor at McGill University (Salon A)
Introduction to Quantum Machine Learning
12h00  13h30 Dîner (Salle 4 canards)
13h30  14h30 Nicolas Godbout, Professor at Polytechnique Montréal (Salon A)
The Micius Satellite Quantum Science Experiments
14h30  15h00 Charles Bédard, Doctorate at Université de Montréal (Salon A)
Kolmogorov Amplification from Bell Correlation
15h00 Mots de clôture (Salon A)
Calilfornia State University, Fullerton
Research as a guide to improve the teaching and learning of quantum mechanics
Quantum mechanics is a notoriously difficult subject, in part because the physical laws of QM contradict what we see in the classical world, which can make it challenging for students to develop a quantum intuition. My research focuses on investigating what specific ideas or concepts are most difficult for students, to what extent the instructional paradigm affects student learning, and how can we use this information to improve instruction. In this talk I will describe a study into how students think about quantum mechanical superposition, and how targeted instruction improved student understanding. Additionally, we will discuss two different instructional paradigms and preliminary data on how they impact student learning.
Doctorate, Université de Montréal
Director: Gilles Brassard
Kolmogorov Amplification from Bell Correlation
It was first observed by John Bell that quantum theory predicts correlations between measurement outcomes that lie beyond the explanatory power of local hidden variable theories. These correlations have traditionally been studied extensively in the probabilistic framework. A drawback of this perspective is that one is then forced to use in a single argument the outcomes of mutuallyexclusive measurements. One of us has initiated an alternative approach, invoking only data at hand, in order to circumvent this issue. In this factual view, which is based on Kolmogorov complexity, we introduce mechanisms such as complexity amplification. We establish that this functionality is realizable, just as its probabilistic counterpart, hereby underlining that Bell correlations are a precious informationprocessing resource.
Doctorate, Université de Sherbrooke
Director: Alexandre Blais
Quantum technology efforts across the globe: leveraging its nearterm impact
Recent years have seen a noticeable interest increase in quantum technologies, now materialized in largescale and worldwide efforts towards strategic use and future commercialization. Moreover, extensive publicity on quantum technologies such as quantum computing, has enhanced their visibility and greatly raised public expectations. In this talk, we contextualize the latest movements in the field to understand their impact on organizations, identifying ways forward towards an effective and longterm collaboration between academic, industrial and media sectors.
Polytechnique Montréal
Tutorial: The Micius Satellite Quantum Science Experiments
McGill Univerity
Attosecond time resolution by AFM
Advancing the time resolution of AFM has been a primary pursuit of multiple research groups [13]. In particular, the idea to observe ultrafast events in the femtosecond range combined with nanometer spatial resolution is of great interest. Here the research focus ranges from measuring photocarriers to the molecule motion and beyond [4]. Recently, we demonstrated picosecond time resolution with non contact atomic force microscopy (ncAFM) and ultrafast laser pulses in low temperature grown GaAs [2].
Our most recent advances in ultrafast time resolution AFM will be presented. We developed an autocorrelation measurement for ultrashort laser pulses by force detection using ncAFM. A nonlinear crystal is used to generate an electric field which follows the intensity of the impinging ultrashort laser pulse; we directly trace the emitted electric field with attosecond temporal, and nanometer spatial, resolution using our ncAFM setup. As such, we are able to demonstrate that the lower limit of time resolution in AFM is solely given by the minimal time delay achievable by the optical setup and the thermal noise of the ncAFM.
[1] M. Takihara, T. Takahashi, T. Ujihara – Appl. Phys. Lett. 93 (2008) 021902.
[2]macher, A. Spielhofer, Y. Miyahara, P. Grutter, Appl. Phys. Lett. 110 (2017) 053111.
Z. Schu[3] G. Shao, M. S. Glaz, F. Ma, H. Ju, D. S. Ginger, ACS Nano, 8 (2014) 10799
[4] M. Peplow, Nature 544 (2017) 408–410.
McGill University
Tutorial: Introduction to Quantum Machine Learning
There has been a lot of talk lately about the importance of Montreal in the context of artificial intelligence and machine learning. combining this with the emergence of quantum technologies, it seems like an opportune moment to learn more about the quantum version of machine learning. I will start with introducing classical machine learning and go through some simple examples, including some details on the coding structure of machine learning. This will serve as a basis to introduce the quantum version of machine learning. This is a much less well defined area with many variants on the degree of "quantumness". I will describe different approaches to quantum machine learning and will give some simple examples and applications, and finish with several open questions.
Université de Sherbrooke
Tutorial: Everything you always wanted to know about theoretical quantum information but were afraid to ask
I will give a tutorial on a topic in theoretical quantum information chosen by the participants.
Research Professional, Université de Sherbrooke
Supervisor: Bertrand Reulet
Third Moment of Current Fluctuations in a Diffusive Conductor
Over the years the study of current fluctuations in coherent conductors, and in particular their variance (second moment), has given new insights in the properties of quasiparticles, such as the effective charge in fractional quantum Hall effect or more recently the symmetry of the Kondo state in carbon nanotubes. Despite this success there has been only a few attempts to push deeper the study of current fluctuations in mesoscopic conductors by tackling the measurement of higher order moments such as the third one. In this presentation I will show the first measurement of third moment of current fluctuations in a diffusive conductor.
Doctorate, Université de Sherbrooke
Director: Alexandre Blais
Itinerant microwave photon detector
The realization of a highefficiency microwave single photon detector is a longstanding problem in the field of microwave quantum optics. We propose a quantum nondemolition, highefficiency photon detector that can readily be implemented in present stateoftheart circuit quantum electrodynamics. This scheme works in a continuous fashion, gaining information about the arrival time of the photon as well as about its presence.
The key insight that allows to circumvent the usual limitations imposed by measurement backaction is the use of longlived dark states in a small ensemble of inhomogeneous artificial atoms to increase the interaction time between the photon and the measurement device.
Using realistic system parameters, we show that large detection fidelities are possible.
Doctorate, Université de Sherbrooke
Director: Bertrand Reulet
Photon statistics of a Josephson parametric amplifier from continuous microwave measurements
The electric ac current flowing though a mesoscopic device exhibits rich electromagnetic fluctuations.[1] Those fluctuations can either be studied through the lens of charge transport or that of quantum optics. In the quantum optics perspective, it is possible to measure the discrete photon statistics of a microwave signal using the cumulants of its continuous voltage fluctuations.[2] I will present recent results for the photon statistics of a Josephson parametric amplifier, the archetypal source of squeezed states in the microwave domain. The results convincingly agree with an inputoutput model of the device and measurement setup.
[1] Rolf Landauer. Nature 392, 658659 (1998)
[2] Virally et al. PRA 93, 043813 (2016)
Master, Université de Sherbrooke
Director: Michel PioroLadrière
Developing a cryogenic CV measurement technique with the goal of it being used for the readout of spin qubits in quantum dots
The use of singleelectron transistors to readout spin qubits in quantum dots has been proven to yield excellent sensitivities. Those high sensitivities are what has allowed singleshot readout to be possible. However, SETs come at a high cost. The fact is that the realestate they occupy is large, sometimes even larger than the space occupied by the quantum dots. This poses significant challenges to the scalability of the quantum dot devices. In this work, we present the base idea for an alternative approach based on quantum capacitance measurement by an external capacitance bridge that would allow the devices to do away with SETs altogether. Some preliminary results using a cryogenic bridge prototype and using a SET as a quantum dot will be shown. As of now, the sensitivity of the prototype is still too low to see Coulomb blockade, but accumulation effects in a SET cooled to cryogenic temperatures were still clearly visible, which shows that the technique we propose could work.
Doctorate, McGill University
Director: Jack Sankey
Design considerations for highreflectivity SiN photonic crystal membranes, and progress toward optical control of mechanical geometry
Photonic crystal membranes exhibit a resonantly enhanced reflectivity. Many applications require this resonance to occur at a prespecified wavelength, imposing stringent geometrical tolerances. Here we tune a freestanding photonic crystal reflector resonance to within 0.15 nm (0.04 linewidths) of 1550 nm using iterative hydrofluoric acid etches, and present a series of simulations for creating reflectors robust against beam collimation [1]. Furthermore, we report progress toward creating a tunable, localized mechanical mode in a phononic crystal using radiation pressure from light [2]. Specifically, we describe fabrication techniques producing consistently 100 nm to 300 nm thick stoichiometric SiN freestanding crystals with an area as large as 20 mm^2, up to 2750 crystal unit cells, and tethers as narrow as ~ 1 um. We interferometrically measure Brownian motion of these crystals and identify a phononic bandgap required for laserinduced localization experiments (with a ratio of gap width to band edge frequency as high as 0.8), consistent with COMSOL simulations. We expect a localization length of ~ 1 unit cell for our optimal devices.
[1] S. Bernard et al., Optics letters 41 (24), 56245627 (2016)
[2] A. Z. Barasheed et al., Phys. Rev. A 93, 053811 (2016)
Doctorate, McGill University
Director: Jack Sankey
Ultrashort HalfCavities for Optomechanical Applications
In the field of optomechanics, we are interested in studying the coupling of light to a mechanical resonator. In a typical experiment, the position of a mechanical oscillator modulates the optical resonant frequency (dispersive coupling) of a FabryPerot optical cavity. In this case, it is advantageous to create optical cavitites that are as small as possible to increase the coupling between light and the motion of mechanical resonators (i.e., small cavities lead to more photon bounces per second on the mechanical resonator). Alternatively, the position of the mechanical element can also modulate the input coupling rate to the cavity (dissipative coupling). We report progress towards creating a micronscale halfcavity formed by a flat mirror and a ~90 nm thick SiN membrane mechanical resonator. By integrating this small halfcavity in a conventional FabryPerot optical resonator, we demonstrate dissipative coupling. This approach to create small cavitites could be used to reduce the dimension of freespace optical cavities down to dimensions comparable to a laser wavelength, yielding an optomechanical coupling rate orders of magnitude higher than with current macroscopic free space systems. It could also enable groundstate cooling of the mechanical oscillator in the "bad cavity" limit.
Doctoreate, McGill University
Director: Bill Coish
Improving preparation and readout fidelity of spinqubits in gated quantum dots
The possibility to construct a working quantum computer depends on the frequency of errors that occur during operation. If the frequency is low enough – estimates for errorcorrection thresholds typically suggest an operation fidelity of more than 99 % – quantum errorcorrection algorithms can counteract these errors. However, these algorithms heavily depend on the readout process of qubits, so that the readout fidelity must be typically on the order of 99.9 % or better.
Although the currently achieved gateoperational fidelity is already at >99.9 % [1], the fidelity of qubit state preparation and readout for single electronspins in gated quantumdots lies at just about 80 % [2] which is too low for realistic applications. Since this technology is a promising platform for scalable quantumcomputers, our goal is to achieve ideally a fidelity of higher than 99.9 %. In that case, a real working quantum computer comes into close reach.
We develop an optimal pulseshape of the given tuningparameter for minimal conversionerrors and at the same time maximal stability to noise in the experimental setup.
[1] J. Yoneda, K. Taked, T. Otsuka, T. Nakajima, M. R. Delbecq, G. Allison, T. Hondea, T. Kodera, S. Oda, Y. Hoshi, N. Usami, K. M. Itoh, S. Tarucha, “A >99.9%fidelity quantumdot spin qubit with coherence limited by charge noise”, arXiv:1708.01454, 4. Aug 2017
[2] T. F. Watson, S. G. J. Philips, E. Kawakami, D. R. Ward, P. Scarlino,, M. Veldhorst, D. E. Savage, M. G. Lagally, Mark Friesen, S. N. Coppersmith, M. A. Eriksson, L. M. K. Vandershypen, “A programmable twoqubit quantum processor in silicon”, arXiv:1708.04214, 14th Aug. 2017
Postdoc, Université de Sherbrooke
Director: Bertrand Reulet
Quantum current fluctuations in a tunnel junction at optical frequency
We report the measurement of emission noise by a planar metallic tunnel junction driven far from its equilibrium state. To investigate this regime, we bias the junction at voltage V>1Volt, and measure the emitted photons at optical frequency (f < eV/h ∼ 1014Hz). This emission results from the scattering of surfaceplasmonpolaritons, generated by high frequency current fluctuations inside the junction due to tunneling electrons (shotnoise). This allows noise measurement at timescales smaller than the RC time of the junction. We show that the emitted photon power Pf(V) at frequency f, which is proportionnal to the current spectral density SII(f,V), isn't given by the usual fluctuationrelation which have been previously demonstrated in the GHz range for metallic and supraconductive linear tunnel junction. Our results are in agreement with a prediction based on the LandauerBüttiker scattering approach accounting for the energy/voltage dependence of the transmission of the tunnel barrier. With a quantitative calculation of the emission efficiency, we demonstrate that the photon emission results from current fluctuations inside the barrier.
Postdoc, McGill University
Director: Lilian Childress
Toward a Tunable Coupling of Optical Microcavities and Color Centers in Diamond
Defect centers in diamond are attractive solidstate candidates for quantum optics experiments. The “flagship” nitrogen vacancy center (NV) is a robust spinqubit platform [1,2]. Unfortunately, ~ 97% of the photons emitted by an NV are useless for spinphoton entanglement protocols.We present our ongoing effort to couple NV and germaniumvacancy (GeV) centers embedded in ultralowloss diamond membranes to a fully tunable optical microcavity directly interfaced with an optical fiber. The required passive and active cavity stabilisation mechanisms will be discussed, as well as our stateoftheart results for the finesse of a cavity loaded with a diamond membrane. We expect that at cryogenic temperatures both NV and GeV decay rates and fraction of “useful” photons will be enhanced, scaling up with the cavity finesse [3]. In addition, GeV centers could also be used to improve the “Indistinguishability x Photon rate” figure of merit for room temperature photon sources.
[1] E. Hogan et al., Nature 466 (2010)
[2] N. Kalb et al., Science 356 (2017)
[3] D. Riedel et al., PRX 7 (2017)
Master, Université de Sherbrooke
Director: Michel PioroLadrière
Frequencytunable microwave cavity with uniform field for coherent control of large spin ensembles
Electron spin resonance (ESR) is a conventional technique for reading and manipulating spin qubits. Many experimental realizations of ESR readout and control use some form of resonant cavity, but most cavity resonator designs are not quickly frequencytunable over a wide frequency range and have a nonuniform microwave field. Uniformity of the microwave field is essential for coherent control of large spin ensembles; using large spin ensembles is desirable because the sensitivity of spin state measurement increases as the square root of the ensemble size. We present an alternative cavity resonator design optimized for ESR experiments. The cavity design provides an uniform field over macroscopic volumes (several mm³) and is dynamically frequencytunable over a large bandwidth by piezoelectric modulation of a flexible copper diaphragm capacitor. This enables applications for quantum sensing technology and general ESR spectroscopy.
Doctorate, Université de Sherbrooke
Director: David Poulin
Critical parameters for quantum error correction
In this work, we present a numerical study to determine the parameters of a single qubit CPTP map that are critical to the estimate of the logical error rate, for a quantum error correction scheme. In particular, our study shows that metrics to quantify the amount of noise in a quantum channel, such as Diamond norm, entanglement fidelity, etc., cannot provide tight bounds on the logical error rate of a quantum error correction scheme. Alternatively we use machine learning techniques to propose a new definition of a physical noise strength for a quantum channel, that provides, in some cases, a more accurate estimate of the logical error rate than previously known metrics.
Master, Université de Sherbrooke
Director: Alexandre Blais
Longitudinal Coupling for Fast QND Measurement: Numerical Study
Dispersive qubit readout in circuit QED relies on transverse coupling to a microwave resonator. This type of coupling, however, leads to mixing between qubit and resonator eigenstates. In turn, this leads to Purcell decay and to a breakdown of the quantum nondemolition (QND) aspect of the measurement associated with the critical number photons. An alternative approach avoiding these two issues is longitudinal qubitresonator coupling [1,2,3]. In our research, we consider circuit realizations of this idea and perform realistic numerical simulations of the longitudinal measurement. We show that the measurement remains QND at higher power than can be expected under transverse coupling. Moreover, comparing transverse and longitudinal qubit readouts, we show that the latter leads to fast and highfidelity QND measurements.
[1] Nicolas Didier, Jérôme Bourassa, and Alexandre Blais, Phys. Rev. Lett. 115, 203601, (2015)
[2] P.M. Billangeon, J. S. Tsai, and Y. Nakamura, Phys. Rev. B 91, 094517, (2015)
[3] Susanne Richer and David DiVincenzo, Phys. Rev. B 93, 134501, (2016)
Master, Université de Sherbrooke
Director: Michel PioroLadrière
Automated tuning of a quantum dot to the single electron regime
In this work, we perform automated tuning of a quantum dot to an operational target for any device equipped and measured using a SET. We first extract the position of electron occupancy transitions in a noisy and featureful signal using the phase of the signal, which is computed using a Hilbert transform. From the transition points, we are able to reconstruct transition lines on a twodimensional stability diagram using image recognition tools. The decision making procedure must be adapted to the gate architecture.
Doctorate, McGill University
Director: Bill Coish
Accurate hyperne tensors for electrons and holes in Si and GaAs
Knowing (and controlling) hyperfine interactions in semiconductor nanostructures is important for quantum information processing with electron, hole, and nuclearspin states. Through a combination of firstprinciples densityfunctional theory calculations and k.p corrections, we have found accurate hyperfine tensors for electrons and holes in GaAs and Si. Our results indicate significant corrections to previous theoretical estimates for the hyperfine coupling of electrons in GaAs and Si, but are consistent with earlier experimental measurements on Knight shifts and Korringa relaxation. In addition, we make new predictions for the hyperfine tensors of both heavy and light holes in the valence band. These calculations are consistent with T_2* times very recently measured for heavy holes in Si quantum dots [1], and with recent measurements on hole spins in InGaAs quantum dots showing an Isinglike hyperfine coupling [2].
[1] Maurand et al., arXiv:1605.07599 (2016)
[2] Prechtel et al., Nat. Mat. 15, 981 (2016)
Märta Tschudin
Master, McGill University
Director: Lilian Childress
Coupling NitrogenVacancy Spins to a Nanomagnet's Ferromagnetic Modes
The nitrogenvacancy (NV) center in diamond is a solid state spin system with long coherence times, with promising applications in quantum information and precision sensing. Optical readout of the spin state allows for the detection of magnetic fields, in principle localized at the nanoscale. Thus far we have fabricated Py/Pt nanowires on singlecrystal diamond having a layer of NV centers implanted 70nm below the surface. Using the injected spintransfer torque from the platinum layer, we can efficiently drive ferromagnetic resonance in the wires, and detect the response via its anisotropic magnetoresistance. Efforts toward observing spatially and spectrallyresolved stray fields using nearby NVs have allowed for detection of the nanomagnet's parametrically driving mode, which may allow for novel ways of controlling NV centers. Finally, we discuss preliminary relaxometry measurements of the coupled NV when only DC currents are applied to gain insight into the magnon mode occupation of the device.
10h30  10h55 Registration
10h55  11h00 Opening remarks (Salon A)
11h00  12h00 Gina Passante, California State University, Fullerton (Salon A)
Research as a guide to improve the teaching and
learning of quantum mechanics
12h00  13h30 Lunch (Dining room)
13h30 14h30 David Poulin, Université de Sherbrooke (Salon A)
Everything you always wanted to know about theoretical
quantum information but were afraid to ask
14h30  15h00 Coffee break (Salon B)
15h00 15h30 Edouard Pinsolle, Université de Sherbrooke (Salon A)
Third Moment of Current Fluctuations in a Diffusive Conductor
15h30  16h00 Jean Olivier Simoneau, Université de Sherbrooke (Salon A)
Photon statistics of a Josephson parametric amplifier
from continuous microwave measurements
16h00  16h30 Agustin Di Paolo, Université de Sherbrooke (Salon A)
Quantum technology efforts across the globe:
leveraging its nearterm impact
16h30  18h30 Poster session with refreshments (Salon B)
19h00  INTRIQ dinner (Room Knowlton)
9h15  10h00 Peter Grüter, Professor at McGill University (Salon A)
Attosecond time resolution by AFM
10h00  10h30 Baptiste Royer, Doctorant at Université de Sherbrooke (Salon A)
Itinerant microwave photon detector
10h30  11h00 Coffee break (Salon B)
11h00  12h00 Michael Hilke, Professor at McGill University (Salon A)
Introduction to Quantum Machine Learning
12h00  13h30 Lunch (Dining room)
13h30  14h30 Nicolas Godbout, Professor at Polytechnique Montréal (Salon A)
The Micius Satellite Quantum Science Experiments
14h30  15h00 Charles Bédard, Doctorate at Université de Montréal (Salon A)
Kolmogorov Amplification from Bell Correlation
15h00 Closing remarks (Salon A)
Calilfornia State University, Fullerton
Research as a guide to improve the teaching and learning of quantum mechanics
Quantum mechanics is a notoriously difficult subject, in part because the physical laws of QM contradict what we see in the classical world, which can make it challenging for students to develop a quantum intuition. My research focuses on investigating what specific ideas or concepts are most difficult for students, to what extent the instructional paradigm affects student learning, and how can we use this information to improve instruction. In this talk I will describe a study into how students think about quantum mechanical superposition, and how targeted instruction improved student understanding. Additionally, we will discuss two different instructional paradigms and preliminary data on how they impact student learning.
Doctorate, Université de Montréal
Director: Gilles Brassard
Kolmogorov Amplification from Bell Correlation
It was first observed by John Bell that quantum theory predicts correlations between measurement outcomes that lie beyond the explanatory power of local hidden variable theories. These correlations have traditionally been studied extensively in the probabilistic framework. A drawback of this perspective is that one is then forced to use in a single argument the outcomes of mutuallyexclusive measurements. One of us has initiated an alternative approach, invoking only data at hand, in order to circumvent this issue. In this factual view, which is based on Kolmogorov complexity, we introduce mechanisms such as complexity amplification. We establish that this functionality is realizable, just as its probabilistic counterpart, hereby underlining that Bell correlations are a precious informationprocessing resource.
Doctorate, Université de Sherbrooke
Director: Alexandre Blais
Quantum technology efforts across the globe: leveraging its nearterm impact
Recent years have seen a noticeable interest increase in quantum technologies, now materialized in largescale and worldwide efforts towards strategic use and future commercialization. Moreover, extensive publicity on quantum technologies such as quantum computing, has enhanced their visibility and greatly raised public expectations. In this talk, we contextualize the latest movements in the field to understand their impact on organizations, identifying ways forward towards an effective and longterm collaboration between academic, industrial and media sectors.
Polytechnique Montréal
Tutorial: The Micius Satellite Quantum Science Experiments
McGill Univerity
Attosecond time resolution by AFM
Advancing the time resolution of AFM has been a primary pursuit of multiple research groups [13]. In particular, the idea to observe ultrafast events in the femtosecond range combined with nanometer spatial resolution is of great interest. Here the research focus ranges from measuring photocarriers to the molecule motion and beyond [4]. Recently, we demonstrated picosecond time resolution with non contact atomic force microscopy (ncAFM) and ultrafast laser pulses in low temperature grown GaAs [2].
Our most recent advances in ultrafast time resolution AFM will be presented. We developed an autocorrelation measurement for ultrashort laser pulses by force detection using ncAFM. A nonlinear crystal is used to generate an electric field which follows the intensity of the impinging ultrashort laser pulse; we directly trace the emitted electric field with attosecond temporal, and nanometer spatial, resolution using our ncAFM setup. As such, we are able to demonstrate that the lower limit of time resolution in AFM is solely given by the minimal time delay achievable by the optical setup and the thermal noise of the ncAFM.
[1] M. Takihara, T. Takahashi, T. Ujihara – Appl. Phys. Lett. 93 (2008) 021902.
[2]macher, A. Spielhofer, Y. Miyahara, P. Grutter, Appl. Phys. Lett. 110 (2017) 053111.
Z. Schu[3] G. Shao, M. S. Glaz, F. Ma, H. Ju, D. S. Ginger, ACS Nano, 8 (2014) 10799
[4] M. Peplow, Nature 544 (2017) 408–410.
McGill University
Tutorial: Introduction to Quantum Machine Learning
There has been a lot of talk lately about the importance of Montreal in the context of artificial intelligence and machine learning. combining this with the emergence of quantum technologies, it seems like an opportune moment to learn more about the quantum version of machine learning. I will start with introducing classical machine learning and go through some simple examples, including some details on the coding structure of machine learning. This will serve as a basis to introduce the quantum version of machine learning. This is a much less well defined area with many variants on the degree of "quantumness". I will describe different approaches to quantum machine learning and will give some simple examples and applications, and finish with several open questions.
Université de Sherbrooke
Tutorial: Everything you always wanted to know about theoretical quantum information but were afraid to ask
I will give a tutorial on a topic in theoretical quantum information chosen by the participants.
Research Professional, Université de Sherbrooke
Supervisor: Bertrand Reulet
Third Moment of Current Fluctuations in a Diffusive Conductor
Over the years the study of current fluctuations in coherent conductors, and in particular their variance (second moment), has given new insights in the properties of quasiparticles, such as the effective charge in fractional quantum Hall effect or more recently the symmetry of the Kondo state in carbon nanotubes. Despite this success there has been only a few attempts to push deeper the study of current fluctuations in mesoscopic conductors by tackling the measurement of higher order moments such as the third one. In this presentation I will show the first measurement of third moment of current fluctuations in a diffusive conductor.
Doctorate, Université de Sherbrooke
Director: Alexandre Blais
Itinerant microwave photon detector
The realization of a highefficiency microwave single photon detector is a longstanding problem in the field of microwave quantum optics. We propose a quantum nondemolition, highefficiency photon detector that can readily be implemented in present stateoftheart circuit quantum electrodynamics. This scheme works in a continuous fashion, gaining information about the arrival time of the photon as well as about its presence.
The key insight that allows to circumvent the usual limitations imposed by measurement backaction is the use of longlived dark states in a small ensemble of inhomogeneous artificial atoms to increase the interaction time between the photon and the measurement device.
Using realistic system parameters, we show that large detection fidelities are possible.
Doctorate, Université de Sherbrooke
Director: Bertrand Reulet
Photon statistics of a Josephson parametric amplifier from continuous microwave measurements
The electric ac current flowing though a mesoscopic device exhibits rich electromagnetic fluctuations.[1] Those fluctuations can either be studied through the lens of charge transport or that of quantum optics. In the quantum optics perspective, it is possible to measure the discrete photon statistics of a microwave signal using the cumulants of its continuous voltage fluctuations.[2] I will present recent results for the photon statistics of a Josephson parametric amplifier, the archetypal source of squeezed states in the microwave domain. The results convincingly agree with an inputoutput model of the device and measurement setup.
[1] Rolf Landauer. Nature 392, 658659 (1998)
[2] Virally et al. PRA 93, 043813 (2016)
Master, Université de Sherbrooke
Director: Michel PioroLadrière
Developing a cryogenic CV measurement technique with the goal of it being used for the readout of spin qubits in quantum dots
The use of singleelectron transistors to readout spin qubits in quantum dots has been proven to yield excellent sensitivities. Those high sensitivities are what has allowed singleshot readout to be possible. However, SETs come at a high cost. The fact is that the realestate they occupy is large, sometimes even larger than the space occupied by the quantum dots. This poses significant challenges to the scalability of the quantum dot devices. In this work, we present the base idea for an alternative approach based on quantum capacitance measurement by an external capacitance bridge that would allow the devices to do away with SETs altogether. Some preliminary results using a cryogenic bridge prototype and using a SET as a quantum dot will be shown. As of now, the sensitivity of the prototype is still too low to see Coulomb blockade, but accumulation effects in a SET cooled to cryogenic temperatures were still clearly visible, which shows that the technique we propose could work.
Doctorate, McGill University
Director: Jack Sankey
Design considerations for highreflectivity SiN photonic crystal membranes, and progress toward optical control of mechanical geometry
Photonic crystal membranes exhibit a resonantly enhanced reflectivity. Many applications require this resonance to occur at a prespecified wavelength, imposing stringent geometrical tolerances. Here we tune a freestanding photonic crystal reflector resonance to within 0.15 nm (0.04 linewidths) of 1550 nm using iterative hydrofluoric acid etches, and present a series of simulations for creating reflectors robust against beam collimation [1]. Furthermore, we report progress toward creating a tunable, localized mechanical mode in a phononic crystal using radiation pressure from light [2]. Specifically, we describe fabrication techniques producing consistently 100 nm to 300 nm thick stoichiometric SiN freestanding crystals with an area as large as 20 mm^2, up to 2750 crystal unit cells, and tethers as narrow as ~ 1 um. We interferometrically measure Brownian motion of these crystals and identify a phononic bandgap required for laserinduced localization experiments (with a ratio of gap width to band edge frequency as high as 0.8), consistent with COMSOL simulations. We expect a localization length of ~ 1 unit cell for our optimal devices.
[1] S. Bernard et al., Optics letters 41 (24), 56245627 (2016)
[2] A. Z. Barasheed et al., Phys. Rev. A 93, 053811 (2016)
Doctorate, McGill University
Director: Jack Sankey
Ultrashort HalfCavities for Optomechanical Applications
In the field of optomechanics, we are interested in studying the coupling of light to a mechanical resonator. In a typical experiment, the position of a mechanical oscillator modulates the optical resonant frequency (dispersive coupling) of a FabryPerot optical cavity. In this case, it is advantageous to create optical cavitites that are as small as possible to increase the coupling between light and the motion of mechanical resonators (i.e., small cavities lead to more photon bounces per second on the mechanical resonator). Alternatively, the position of the mechanical element can also modulate the input coupling rate to the cavity (dissipative coupling). We report progress towards creating a micronscale halfcavity formed by a flat mirror and a ~90 nm thick SiN membrane mechanical resonator. By integrating this small halfcavity in a conventional FabryPerot optical resonator, we demonstrate dissipative coupling. This approach to create small cavitites could be used to reduce the dimension of freespace optical cavities down to dimensions comparable to a laser wavelength, yielding an optomechanical coupling rate orders of magnitude higher than with current macroscopic free space systems. It could also enable groundstate cooling of the mechanical oscillator in the "bad cavity" limit.
Doctoreate, McGill University
Director: Bill Coish
Improving preparation and readout fidelity of spinqubits in gated quantum dots
The possibility to construct a working quantum computer depends on the frequency of errors that occur during operation. If the frequency is low enough – estimates for errorcorrection thresholds typically suggest an operation fidelity of more than 99 % – quantum errorcorrection algorithms can counteract these errors. However, these algorithms heavily depend on the readout process of qubits, so that the readout fidelity must be typically on the order of 99.9 % or better.
Although the currently achieved gateoperational fidelity is already at >99.9 % [1], the fidelity of qubit state preparation and readout for single electronspins in gated quantumdots lies at just about 80 % [2] which is too low for realistic applications. Since this technology is a promising platform for scalable quantumcomputers, our goal is to achieve ideally a fidelity of higher than 99.9 %. In that case, a real working quantum computer comes into close reach.
We develop an optimal pulseshape of the given tuningparameter for minimal conversionerrors and at the same time maximal stability to noise in the experimental setup.
[1] J. Yoneda, K. Taked, T. Otsuka, T. Nakajima, M. R. Delbecq, G. Allison, T. Hondea, T. Kodera, S. Oda, Y. Hoshi, N. Usami, K. M. Itoh, S. Tarucha, “A >99.9%fidelity quantumdot spin qubit with coherence limited by charge noise”, arXiv:1708.01454, 4. Aug 2017
[2] T. F. Watson, S. G. J. Philips, E. Kawakami, D. R. Ward, P. Scarlino,, M. Veldhorst, D. E. Savage, M. G. Lagally, Mark Friesen, S. N. Coppersmith, M. A. Eriksson, L. M. K. Vandershypen, “A programmable twoqubit quantum processor in silicon”, arXiv:1708.04214, 14th Aug. 2017
Postdoc, Université de Sherbrooke
Director: Bertrand Reulet
Quantum current fluctuations in a tunnel junction at optical frequency
We report the measurement of emission noise by a planar metallic tunnel junction driven far from its equilibrium state. To investigate this regime, we bias the junction at voltage V>1Volt, and measure the emitted photons at optical frequency (f < eV/h ∼ 1014Hz). This emission results from the scattering of surfaceplasmonpolaritons, generated by high frequency current fluctuations inside the junction due to tunneling electrons (shotnoise). This allows noise measurement at timescales smaller than the RC time of the junction. We show that the emitted photon power Pf(V) at frequency f, which is proportionnal to the current spectral density SII(f,V), isn't given by the usual fluctuationrelation which have been previously demonstrated in the GHz range for metallic and supraconductive linear tunnel junction. Our results are in agreement with a prediction based on the LandauerBüttiker scattering approach accounting for the energy/voltage dependence of the transmission of the tunnel barrier. With a quantitative calculation of the emission efficiency, we demonstrate that the photon emission results from current fluctuations inside the barrier.
Postdoc, McGill University
Director: Lilian Childress
Toward a Tunable Coupling of Optical Microcavities and Color Centers in Diamond
Defect centers in diamond are attractive solidstate candidates for quantum optics experiments. The “flagship” nitrogen vacancy center (NV) is a robust spinqubit platform [1,2]. Unfortunately, ~ 97% of the photons emitted by an NV are useless for spinphoton entanglement protocols.We present our ongoing effort to couple NV and germaniumvacancy (GeV) centers embedded in ultralowloss diamond membranes to a fully tunable optical microcavity directly interfaced with an optical fiber. The required passive and active cavity stabilisation mechanisms will be discussed, as well as our stateoftheart results for the finesse of a cavity loaded with a diamond membrane. We expect that at cryogenic temperatures both NV and GeV decay rates and fraction of “useful” photons will be enhanced, scaling up with the cavity finesse [3]. In addition, GeV centers could also be used to improve the “Indistinguishability x Photon rate” figure of merit for room temperature photon sources.
[1] E. Hogan et al., Nature 466 (2010)
[2] N. Kalb et al., Science 356 (2017)
[3] D. Riedel et al., PRX 7 (2017)
Master, Université de Sherbrooke
Director: Michel PioroLadrière
Frequencytunable microwave cavity with uniform field for coherent control of large spin ensembles
Electron spin resonance (ESR) is a conventional technique for reading and manipulating spin qubits. Many experimental realizations of ESR readout and control use some form of resonant cavity, but most cavity resonator designs are not quickly frequencytunable over a wide frequency range and have a nonuniform microwave field. Uniformity of the microwave field is essential for coherent control of large spin ensembles; using large spin ensembles is desirable because the sensitivity of spin state measurement increases as the square root of the ensemble size. We present an alternative cavity resonator design optimized for ESR experiments. The cavity design provides an uniform field over macroscopic volumes (several mm³) and is dynamically frequencytunable over a large bandwidth by piezoelectric modulation of a flexible copper diaphragm capacitor. This enables applications for quantum sensing technology and general ESR spectroscopy.
Doctorate, Université de Sherbrooke
Director: David Poulin
Critical parameters for quantum error correction
In this work, we present a numerical study to determine the parameters of a single qubit CPTP map that are critical to the estimate of the logical error rate, for a quantum error correction scheme. In particular, our study shows that metrics to quantify the amount of noise in a quantum channel, such as Diamond norm, entanglement fidelity, etc., cannot provide tight bounds on the logical error rate of a quantum error correction scheme. Alternatively we use machine learning techniques to propose a new definition of a physical noise strength for a quantum channel, that provides, in some cases, a more accurate estimate of the logical error rate than previously known metrics.
Master, Université de Sherbrooke
Director: Alexandre Blais
Longitudinal Coupling for Fast QND Measurement: Numerical Study
Dispersive qubit readout in circuit QED relies on transverse coupling to a microwave resonator. This type of coupling, however, leads to mixing between qubit and resonator eigenstates. In turn, this leads to Purcell decay and to a breakdown of the quantum nondemolition (QND) aspect of the measurement associated with the critical number photons. An alternative approach avoiding these two issues is longitudinal qubitresonator coupling [1,2,3]. In our research, we consider circuit realizations of this idea and perform realistic numerical simulations of the longitudinal measurement. We show that the measurement remains QND at higher power than can be expected under transverse coupling. Moreover, comparing transverse and longitudinal qubit readouts, we show that the latter leads to fast and highfidelity QND measurements.
[1] Nicolas Didier, Jérôme Bourassa, and Alexandre Blais, Phys. Rev. Lett. 115, 203601, (2015)
[2] P.M. Billangeon, J. S. Tsai, and Y. Nakamura, Phys. Rev. B 91, 094517, (2015)
[3] Susanne Richer and David DiVincenzo, Phys. Rev. B 93, 134501, (2016)
Master, Université de Sherbrooke
Director: Michel PioroLadrière
Automated tuning of a quantum dot to the single electron regime
In this work, we perform automated tuning of a quantum dot to an operational target for any device equipped and measured using a SET. We first extract the position of electron occupancy transitions in a noisy and featureful signal using the phase of the signal, which is computed using a Hilbert transform. From the transition points, we are able to reconstruct transition lines on a twodimensional stability diagram using image recognition tools. The decision making procedure must be adapted to the gate architecture.
Doctorate, McGill University
Director: Bill Coish
Accurate hyperne tensors for electrons and holes in Si and GaAs
Knowing (and controlling) hyperfine interactions in semiconductor nanostructures is important for quantum information processing with electron, hole, and nuclearspin states. Through a combination of firstprinciples densityfunctional theory calculations and k.p corrections, we have found accurate hyperfine tensors for electrons and holes in GaAs and Si. Our results indicate significant corrections to previous theoretical estimates for the hyperfine coupling of electrons in GaAs and Si, but are consistent with earlier experimental measurements on Knight shifts and Korringa relaxation. In addition, we make new predictions for the hyperfine tensors of both heavy and light holes in the valence band. These calculations are consistent with T_2* times very recently measured for heavy holes in Si quantum dots [1], and with recent measurements on hole spins in InGaAs quantum dots showing an Isinglike hyperfine coupling [2].
[1] Maurand et al., arXiv:1605.07599 (2016)
[2] Prechtel et al., Nat. Mat. 15, 981 (2016)
Märta Tschudin
Master, McGill University
Director: Lilian Childress
Coupling NitrogenVacancy Spins to a Nanomagnet's Ferromagnetic Modes
The nitrogenvacancy (NV) center in diamond is a solid state spin system with long coherence times, with promising applications in quantum information and precision sensing. Optical readout of the spin state allows for the detection of magnetic fields, in principle localized at the nanoscale. Thus far we have fabricated Py/Pt nanowires on singlecrystal diamond having a layer of NV centers implanted 70nm below the surface. Using the injected spintransfer torque from the platinum layer, we can efficiently drive ferromagnetic resonance in the wires, and detect the response via its anisotropic magnetoresistance. Efforts toward observing spatially and spectrallyresolved stray fields using nearby NVs have allowed for detection of the nanomagnet's parametrically driving mode, which may allow for novel ways of controlling NV centers. Finally, we discuss preliminary relaxometry measurements of the coupled NV when only DC currents are applied to gain insight into the magnon mode occupation of the device.