High-Fidelity and Ultrafast Initialization of a Hole Spin Bound to a Te Isoelectronic Center in ZnS

We demonstrate the optical initialization of a hole-spin qubit bound to an isoelectronic center (IC) formed by a pair of Te impurities in ZnSe, an impurity/host system providing high optical homogeneity, large electric dipole moments, and long coherence times. The initialization scheme is based on the spin-preserving tunneling of a resonantly excited donor-bound exciton to a positively charged Te IC, thus forming a positive trion. The radiative decay of the trion within less than 50 ps leaves a heavy hole in a well-defined polarization-controlled spin state. The initialization fidelity exceeds 98:5 % for an initialization time of less than 150 ps.Comment: 5 pages, 3 figures, 1 supplemental information sectio

Statistique de maxima et modèles graphiques multi-échelles : application à la turbulence

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Dynamics of Excitonic Complexes Bound to Isoelectronic Centers: Toward the Realization of Optically Addressable Qubits

La réalisation de qubits pouvant être couplés efficacement à des photons optiques est nécessaire pour réaliser la transmission d’information quantique à longue distance, par exemple à l’intérieur d’un réseau quantique. Le principal obstacle empêchant la réalisation de ces qubits addressables optiquement vient de la grande difficulté de trouver une plateforme offrant à la fois une grande homogénéité et un fort couplage optique. Les centres isoélectroniques (CIs),qui sont des impuretés isovalentes à l’intérieur d’un matériau semi-conducteur, représentent une alternative fort intéressante aux systèmes de qubits adressables optiquement proposés dans la littérature, soit les boîtes quantiques auto-assemblées et les centres NV dans le diamant souffrant, respectivement, d’un fort élargissement inhomogène et d’un couplage optique moins grand que les CIs. En effet, la nature atomique des CIs leur assure une homogénéité comparable aux centres NV et leur capacité à lier des complexes excitoniques présentant de forts moments dipolaires permet d’obtenir un couplage avec les champs photoniques aussi fort que dans les boîtes quantiques. Le but du travail présenté dans cette thèse est d’évaluer le potentiel de différents complexes excitoniques liés à ces CIs pour fabriquer des qubits adressables optiquement. Cette thèse par articles est séparée en deux grandes sections. Dans la première section, correspondant aux articles 1 et 2, j’ai étudié les caractéristiques physiques de qubits excitoniques liés à des CIs d’azote dans le GaP (Article 1) et le GaAs (Article 2). Plus précisément, ces articles présentent une analyse approfondie combinant des mesures de photoluminescence résolue dans le temps et des modèles de balance de populations afin d’identifier et de quantifier les différents mécanismes impliqués dans la dynamique de recombinaison des excitons. Dans la seconde section, j’ai démontré l’initialisation d’un qubit de spin de trou lié à un centre isoélectronique de Te dans une matrice de ZnSe. Contrairement aux qubits excitoniques, la cohérence des qubits de spin n’est pas limitée par leur émission spontanée permettant ainsi d’atteindre des temps de cohérence beaucoup plus intéressants. Le premier article de cette thèse présente une étude de la dynamique de recombinaison des excitons liés à des CIs d’azote dans le GaP. Le principal avantage relié à l’étude de ce système vient du fait qu’une grande variété de centres sont accessibles : ils peuvent être formés de 1,2 ou 3 impuretés d’azote et présenter différentes symétries à l’intérieur du matériau hôte.----------Abstract The realization of qubits that can be efficiently coupled to optical fields is necessary for long distance transmission of quantum information, e.g. inside quantum networks. The principal hurdle preventing the realization of such optically addressable qubits arises from the challenging task of finding a platform that offers as well high optical homogeneity and strong light-matter coupling. In regard to this challenge, isoelectronic centers (ICs), which are isovalent impurities in a semiconductor host, represent a very promising alternative to the well-studied epitaxial quantum dots and NV centers in diamond which suffer, respectively,from a large inhomogeneous broadening and a less effective coupling to optical fields than ICs. Indeed, the atomic nature of ICs insures an optical homogeneity comparable to NV centers, and their ability to bind excitonic complexes with strong electric dipole moments allows them to offer an optical coupling similar to quantum dots. The aim of the work presented in this thesis is to evaluate the potential of different excitonic complexes bound to these ICs for building optically addressable qubits. This thesis by articles, is separated in two parts. In the first part, corresponding to Article 1 and 2, I study the physics of exciton qubits bound to N ICs in GaP (Article 1) and in GaAas (Article 2). More precisely, these articles present an analysis combining time-resolve PL measurements and balance of population models, allowing to identify and quantify the different mechanisms involved in the exciton recombination dynamics. In the second part, I demonstrate the initialization of a hole-spin qubit bound to a Te IC in ZnSe. Contrary to exciton qubits the coherence time of spin qubit is not limited by their spontaneous emission, allowing to preserve coherence on a much more significant timescale. The first article of this thesis presents a study of the recombination dynamics of excitons bound to N ICs in GaP. The principal advantage of studying this system comes from the large variety of atomic configurations that can be accessed: ICs can be formed from one, two or three impurities, and exhibit different local symmetries inside the host lattice. Although it appears very challenging to realize optically addressable qubits in this system due to its low coupling to optical fields, it has allowed for a better understanding of how the atomic configuration of the underlying IC influences the different mechanisms involved in exciton recombination dynamics (capture, inter-level transfers, and radiative and non-radiative recombination)

Aide au processus décisionnel pour la gestion par bassin versant au Québec : étude de cas et principaux enjeux

Les conditions particulières prévalant lors de l’application d’une approche de gestion par bassin versant au Québec (Canada) font appel à de nouvelles méthodologies intégrées pour faciliter l’analyse et le partage des informations, les conditions de négociation entre les parties prenantes et la mise en oeuvre des choix d’aménagement ou de gestion retenus. Cet article met en perspective la modélisation des processus décisionnels territoriaux à l’échelle des bassins versants (BV). Il dégage certains enjeux méthodologiques se rattachant à cette problématique de gestion dans sa dimension informationnelle, dans le contexte du Québec. Il montre l’interconnexion des préoccupations décisionnelles aux conditions d’utilisation d’une plate-forme géomatique à même de modéliser de tels processus territoriaux dans le cadre d’un système intégré d’aide à la décision (SIAD). Finalement, il recommande l’évaluation de l’utilisation d’un tel système (SIAD-BV) pour faciliter l’émergence des conditions d’application de l’approche de la gestion intégrée par bassin versant au Québec, à partir des discussions réalisées avec des intervenants des bassins Chaudière et Outaouais.The unique conditions that prevail when a political approach to watershed management in Quebec (Canada) is taken, requires a need for integrated methodologies to promote the following: information sharing and analysis, negotiation of conditions among stakeholders and introduction of selected management alternatives. This article brings the modelling of regional decision-making processes that apply to watershed management (WM) into perspective. It discusses the methodological challenges relating to information that are inherent to this management issue, particularly in a Québec (Canada) context. It shows links between decisional concerns and geomatic skills for modelling these regional processes, as an integrated decision support system (IDSS). Lastly, it recommends assessing the use of this type of system to promote the emergence of conditions where such an approach to watershed management in Québec could be implemented, based on interviews conducted with regional professionals in the Chaudière and Outaouais basins

La justice réparatrice telle que conçue par les victimes et les adolescents contrevenants

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Advanced bioengineering technologies for preclinical research

Current in vitro practices must overcome important challenges to compare favorably with human studies. The limited applicability of conventional in vitro assays and strategies can be explained by the fact that standard approaches do not enable recapitulation of the complexity of human tissues and physiological functions. To address this challenge, novel bioengineering tools, techniques and technologies are rapidly emerging to advance current fundamental knowledge and innovate in vitro practices. For example, organs-on-a-chip have recently appeared as a small-scale solution to overcome the transability, financial and ethical concerns associated with animal studies in drug discovery and development. In parallel, biomimetic interfaces are increasingly recapitulating 3D structures with tissue-like dynamic properties to allow in-depth investigation of disease mechanisms. This review aims at highlighting current bioengineering approaches poised to address the shortcomings of conventional in vitro research practices towards the generation of more effective solutions for improving human health

Orbital angular momentum bistability in a microlaser

Light's orbital angular momentum (OAM) is an unbounded degree of freedom emerging in helical beams that appears very advantageous technologically. Using a chiral microlaser, i.e. an integrated device that allows generating an emission carrying a net OAM, we demonstrate a regime of bistability involving two modes presenting distinct OAM (L = 0 and L = 2). Furthermore, thanks to an engineered spin-orbit coupling of light in the device, these modes also exhibit distinct polarization patterns, i.e. cirular and azimuthal polarizations. Using a dynamical model of rate euqations, we show that this bistability arises from polarization-dependent saturation of the gain medium. Such a bistable regime appears very promising for implementing ultrafast optical switches based on the OAM of light. As well, it paves the way to the exploration of dynamical processes involving phase and polarization vortices

Tracking larvae with molecular markers reveals high relatedness and early seasonal recruitment success in a partially spawning marine bivalve

The partial synchronized spawning strategy\ud adopted by some marine invertebrate broadcast-spawners\ud can lead to the production of many distinct pools of larvae\ud within a single reproductive cycle. Following the fate of\ud these larval groups from birth to settlement with molecular\ud markers might shed light on mechanisms regulating their\ud population recruitment. Larvae and recruits of Mya arenaria,\ud a partially spawning marine bivalve, were monitored\ud and collected over 13 consecutive weeks during an entire\ud reproductive cycle. Each sampled individual (n = 218)\ud was sorted according to size (early veligers, late veligers,\ud post-larval recruits) and genotyped at seven microsatellite\ud loci for comparisons among samples and with adult reference\ud samples (n = 270). While traditional differentiation\ud statistics (e.g., pairwise ϴST, allelic richness) suggested\ud the absence of sweepstakes reproductive success, the level of relatedness found within and among larvae and recruit\ud samples suggested otherwise. Four samples out of ten were\ud observed to have higher within-sample relatedness values\ud than randomly expected, including the very first group\ud of early veligers produced in the season (E1) and the last\ud group of post-larvae who survived recruitment (P10). E1\ud individuals were also found to be more related than randomly\ud expected to individuals of more than 80 % of all\ud other samples including the last surviving recruits (P8 and\ud P10). These results suggest that the first larvae produced\ud in the season were the most successful to survive recruitment.\ud Results also show direct evidence for larval retention\ud and demonstrate for the first time larval and post-larval kin\ud aggregation in a marine bivalve

Autonomous quantum error correction of Gottesman-Kitaev-Preskill states

The Gottesman-Kitaev-Preskill (GKP) code encodes a logical qubit into a bosonic system with resilience against single-photon loss, the predominant error in most bosonic systems. Here we present experimental results demonstrating quantum error correction of GKP states based on reservoir engineering of a superconducting device. Error correction is made autonomous through an unconditional reset of an auxiliary transmon qubit. The lifetime of the logical qubit is shown to be increased from quantum error correction, therefore reaching the point at which more errors are corrected than generated.Comment: 6 pages, 3 figures + 26 pages, 12 figure