Control and characterization of a spin-orbit-driven singlet-triplet qubit in silicon

Les spins dans les semi-conducteurs sont d’excellents candidats pour l’implémentation d’un ordinateur quantique universel puisqu’ils sont compacts, peuvent être opérés à des températures relativement élevées, ont le potentiel d’atteindre des temps de cohérence très longs, et peuvent être combinés avec d’autres technologies quantiques pour former des systèmes hybrides. En particulier, les dispositifs fabriqués en silicium isotopiquement enrichi offrent des fidélités accrues et ont un processus de fabrication compatible avec les techniques utilisées dans les fonderies CMOS. Cette thèse étudie un qubit singulet-triplet confiné dans une boîte quantique double en silicium isotopiquement enrichi. Dans la première partie, cette thèse montre comment caractériser et ajuster la double boîte pour atteindre le régime de contrôle désiré. Une méthode numérique est développée pour trianguler la position des boîtes quantiques et des donneurs implantés dans le substrat. Un nouveau modèle permettant de prédire les taux tunnel en fonction des voltages de grille est également proposé, puis vérifié expérimentalement. Dans la deuxième partie, cette thèse montre comment implémenter le contrôle résolu en temps d’un qubit singulettriplet entraîné par l’interaction spin-orbite. Deux méthodes différentes permettant d’implémenter des rotations arbitraire sur un qubit sont démontrées : la méthode pulsée (DC) et la méthode résonante (AC). Il est montré que le régime où le qubit est fortement entraîné peut être atteint à l’aide de ces portes résonantes. Finalement, la tomographie d’ensemble de portes (gate set tomography) est utilisée pour comparer ces deux types de portes logiques. Les résultats semblent indiquer que les portes résonantes sont de plus haute fidélité que les portes pulsées, et cela malgré le fait qu’elles soient plus lentes et qu’elles aient un facteur de qualité plus petit que ces dernières. Ces travaux sont les premiers à utiliser cette méthode tomographique pour caractériser des rotations autour de deux axes non-orthogonaux.Abstract : Spins in semiconductors are attractive candidates for a universal quantum computer because they are compact, can be operated at relatively high temperature, have potentially long coherence times, and can be combined with other quantum technologies to form hybrid systems. Devices made using isotopically-enriched silicon offer the additional advantages of increased coherence time due to the relative absence of nuclear spins, and compatibility with existing CMOS foundry fabrication techniques. This work studies a singlet-triplet qubit formed in an enriched silicon metal-oxide-semiconductor double quantum dot device. The first part of this thesis presents techniques that are useful for characterizing the double-dot device and tuning it to the few electron regime. A capacitance-based numerical method is developed to triangulate the position of quantum dots and implanted donor atoms. Additionally, a new model that predicts dot-lead tunnel rates for varying gate voltages is proposed and its validity is demonstrated over a wide range of values. The second part of this thesis shows how to perform time domain control on a spin-orbit-driven singlet-triplet qubit. Two different methods for performing arbitrary single-qubit rotations are demonstrated: fast DC-controlled pulses, and slower resonantly-driven AC pulses. Evidence of the resonantly-driven pulses being pushed to the strongly-driven regime is shown. The final part of this thesis uses gate set tomography to compare the fidelity of these two types of single-qubit operations. Preliminary results seem to indicate that the resonantly-driven rotations have a higher fidelity than the DC-controlled operations despite the fact that the former are slower and have a smaller quality factor than the latter. This work constitutes the first time that gate set tomography is used to characterize a non-orthogonal set of gates

Maine, The Union\u27s Aurora: A Maine Centennial Poem, 1820-1920

Born December 1879 in Vinalhaven, Maine Beulah Sylvester Oxton (1879-1924) was a teacher in the Bar Harbor school system, Maine writer and poet. She was a member of the Maine Writers\u27 Research Club.https://digitalcommons.library.umaine.edu/mainebicentennial/1012/thumbnail.jp

A Comparison of the Effects of Weight Control and Reduction of High School Wrestlers on Selected Measurements of Strength

The purpose of this study was to determine the changes, if any, of selected strength factors of typical North Dakota high school wrestlers, as these might be affected by programs of weight reduction or weight control. Right grip, left grip, push, pull, leg and back strength data of the subjects were recorded using a dynamometer. The subjects were tested five times during and after the season. Inter-group and intra-group comparisons of results were made between the control group consisting of seven high school wrestlers and the experimental group of seven high school wrestlers who experienced a weight loss of more than 3 per cent. A comparison of mean differences found no significance for five of the areas tested. Push strength experienced a significant difference in favor of the experimental group in between group comparisons of Test 1 to Test 5, Test 2 to Test 3, Test 2 to Test 4. The average weight loss for the experimental group from Test 1 to Test 2 was 4.6 per cent of normal body weight taken at the time of pre-season weigh-in. The average weight gain for all wrestlers from Test 2 to Test 5 was 7.4 per cent of the post season weight

Skeptics and Unruly Connectives: A Defence of and Amendment to the Non-Factualist Justification of Logic

This thesis attempts to positively solve three problems in the foundations of logic. If logical connectives are defined by their introduction and elimination rules, then how might one prohibit the construction of dysfunctional rules, i.e. rules which let us infer anything from anything else? How might one be held accountable to the consequences of those logical rules that they accept in an argument? And, how might one who, for whatever reason, doubts those logical rules regularly taken for granted, be convinced to adopt deductive ‘best practices?’ A variety of positions in the foundations of logic are reviewed, but it is found that each either fails to answer all questions together, or leads one to troubling epistemic conclusions. This thesis attempts to draw broad lessons from those positions otherwise found wanting, and then builds on the seemingly most plausible perspective; namely, non-factualism. Particularly, it is argued that non-factualism fails to distinguish between epistemic values and epistemic domains, and that the consequence of this distinction allows one to effectively compare the success of their deductive practices with the skeptic

Fabrication de nanoaimants pour le contrôle rapide d'un spin électronique dans une boîte quantique double

Un ordinateur quantique est un ordinateur formé de bits quantiques (qubits) qui tire profit des propriétés quantiques de la matière. Un grand intérêt est porté au développement d’un tel ordinateur depuis qu’il a été montré que le calcul quantique permettrait d’effectuer certains types de calculs exponentiellement plus rapidement qu’avec les meilleurs algorithmes connus sur un ordinateur classique. D’ailleurs, plusieurs algorithmes ont déjà été suggérés pour résoudre efficacement des problèmes tels que la factorisation de grands nombres premiers et la recherche dans des listes désordonnées. Avant d’en arriver à un ordinateur quantique fonctionnel, certains grands défis doivent être surmontés. Un de ces défis consiste à fabriquer des qubits ayant un temps d’opération nettement inférieur au temps de cohérence (temps durant lequel l’état du qubit est conservé). Cette condition est nécessaire pour parvenir à un calcul quantique fiable. Pour atteindre cet objectif, de nombreuses recherches visent à augmenter le temps de cohérence en choisissant judicieusement les matériaux utilisés dans la fabrication des qubits en plus d’imaginer de nouvelles méthodes d’utiliser ces dispositifs pour diminuer la durée des opérations. Une manière simple d’implémenter un qubit est de piéger quelques électrons dans l’espace et d’utiliser l’état de spin de cet ensemble d’électrons pour encoder les états du qubit. Ce type de dispositif porte le nom de qubit de spin. Les boîtes quantiques (BQs) latérales fabriquées sur des substrats de GaAs/AlGaAs sont un exemple de qubit de spin et sont les dispositifs étudiés dans ce mémoire. En 2007, Pioro-Ladrière et al. ont suggéré de placer un microaimant à proximité d’une BQ pour créer un gradient de champ magnétique non-uniforme et permettre d’effectuer des rotations de spin à l’aide d’impulsions électriques rapides. Ce mémoire présente comment modifier la géométrie de ces microaimants pour obtenir un plus grand gradient de champ magnétique dans la BQ. Une nouvelle technique de contrôle de spin menant à des rotations de spin et de phase plus rapides sera aussi détaillée. Enfin, il sera montré que le département de physique de l’Université de Sherbrooke possède tous les outils nécessaires pour implémenter cette méthode

Vibrational analysis of Ag3(PO2NH)3, Na3(PO2NH)3.H2O, Na3(PO2NH)3.4H2O, [C(NH2)3]3(PO2NH)3.H2O and (NH4)4(PO2NH)4.4H2O

FT IR and FT Raman spectra of Ag3(PO2NH), (Compound I), Na3(PO2NH)3.H2O (Compound II), Na3(PO2NH)3.4H2O (Compound III), [C(NH2)3]3(PO2NH)3.H2O (Compound IV) and (NH4)4(PO2NH)4.4H2O (Compound V) are recorded and analyzed on the basis of the anions, cations and water molecules present in each of them. The PO2NH− anion ring in compound I is distorted due to the influence of Ag+ cation. Wide variation in the hydrogen bond lengths in compound III is indicated by the splitting of the v2 and v3 modes of vibration of water molecules. The NH4 ion in compound V occupies lower site symmetry and exhibits hindered rotation in the lattice. The correlations between the symmetric and asymmetric stretching vibrations of P-N-P bridge and the P-N-P bond angle have also been discussed

A novel formulation of inhaled sodium cromoglicate (PA101) in idiopathic pulmonary fibrosis and chronic cough: a randomised, double-blind, proof-of-concept, phase 2 trial

Background Cough can be a debilitating symptom of idiopathic pulmonary fibrosis (IPF) and is difficult to treat. PA101 is a novel formulation of sodium cromoglicate delivered via a high-efficiency eFlow nebuliser that achieves significantly higher drug deposition in the lung compared with the existing formulations. We aimed to test the efficacy and safety of inhaled PA101 in patients with IPF and chronic cough and, to explore the antitussive mechanism of PA101, patients with chronic idiopathic cough (CIC) were also studied. Methods This pilot, proof-of-concept study consisted of a randomised, double-blind, placebo-controlled trial in patients with IPF and chronic cough and a parallel study of similar design in patients with CIC. Participants with IPF and chronic cough recruited from seven centres in the UK and the Netherlands were randomly assigned (1:1, using a computer-generated randomisation schedule) by site staff to receive PA101 (40 mg) or matching placebo three times a day via oral inhalation for 2 weeks, followed by a 2 week washout, and then crossed over to the other arm. Study participants, investigators, study staff, and the sponsor were masked to group assignment until all participants had completed the study. The primary efficacy endpoint was change from baseline in objective daytime cough frequency (from 24 h acoustic recording, Leicester Cough Monitor). The primary efficacy analysis included all participants who received at least one dose of study drug and had at least one post-baseline efficacy measurement. Safety analysis included all those who took at least one dose of study drug. In the second cohort, participants with CIC were randomly assigned in a study across four centres with similar design and endpoints. The study was registered with ClinicalTrials.gov (NCT02412020) and the EU Clinical Trials Register (EudraCT Number 2014-004025-40) and both cohorts are closed to new participants. Findings Between Feb 13, 2015, and Feb 2, 2016, 24 participants with IPF were randomly assigned to treatment groups. 28 participants with CIC were enrolled during the same period and 27 received study treatment. In patients with IPF, PA101 reduced daytime cough frequency by 31·1% at day 14 compared with placebo; daytime cough frequency decreased from a mean 55 (SD 55) coughs per h at baseline to 39 (29) coughs per h at day 14 following treatment with PA101, versus 51 (37) coughs per h at baseline to 52 (40) cough per h following placebo treatment (ratio of least-squares [LS] means 0·67, 95% CI 0·48–0·94, p=0·0241). By contrast, no treatment benefit for PA101 was observed in the CIC cohort; mean reduction of daytime cough frequency at day 14 for PA101 adjusted for placebo was 6·2% (ratio of LS means 1·27, 0·78–2·06, p=0·31). PA101 was well tolerated in both cohorts. The incidence of adverse events was similar between PA101 and placebo treatments, most adverse events were mild in severity, and no severe adverse events or serious adverse events were reported. Interpretation This study suggests that the mechanism of cough in IPF might be disease specific. Inhaled PA101 could be a treatment option for chronic cough in patients with IPF and warrants further investigation