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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Uma visão contemporânea de alguns conceitos da teoria quântica

Bernardo, Bertúlio de Lima 06 June 2013 (has links)
Made available in DSpace on 2015-05-14T12:14:08Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1944924 bytes, checksum: e08f0978e6406af124c9fe4875d2aa1e (MD5) Previous issue date: 2013-06-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this thesis we discuss some fundamental aspects of the quantum theory from a contemporaneous point of view, where we could develop three works. In the first we analyze theoretically an atomic double-slit interferometer. It has been shown that if the energy eigenstates of the atom are correlated with its particle and wave behaviors, complementary phenomena can be measured simultaneously, indicating a reinterpretation of the complementarity principle. We also demonstrate that this experiment possesses quantum erasure properties. In the second we present a two-particle interferometer in order to analyze the way in which decoherence affects quantum interference. It has been shown how the environmental constituents, here considered as photons, can destroy the oscillations in the coincidence detection rate of the particles. Due to the temporal characteristic of this kind of interference, we name this process as quantum temporal decoherence. In the last work we study the existence of a novel complete family of exact and orthogonal solutions of the paraxial wave equation. The complex amplitude of these beams is proportional to the confluent hypergeometric functions, which we name hypergeometric modes of type-II (HyG-II). It is formally demonstrated that a hyperbolic-index medium can generate and support the propagation of such a class of beams. Since these modes are eigenfunctions of the photon orbital angular momentum, we conclude that an optical fiber with hyperbolic-index profile could take advantage over other graded-index fibers by the capacity of data transmission. / Nesta tese discutimos alguns aspectos fundamentais da teoria quântica de um ponto de vista mais contemporâneo, onde também pudemos desenvolver três trabalhos. No primeiro analisamos teoricamente um interferômetro de fenda dupla para átomos. Mostramos que se os autoestados de energia do átomo estão correlacionados com os comportamentos de partícula e de onda do mesmo, fenômenos complementares podem ser medidos simultaneamente, indicando uma reinterpretação do princípio da complementaridade. O mesmo aparato também apresentou propriedades de apagador quântico. No segundo apresentamos um interferômetro de duas partículas e a maneira como a decoerência afeta o grau de interferência. Mostramos como os constituintes do ambiente, aqui considerados como fótons, podem destruir a oscilação na taxa de coincidência de detecção das partículas. Devido a sua característica temporal, chamamos este processo de decoerência temporal quântica. No último trabalho estudamos a existência de uma nova família de soluções ortogonais da equação paraxial da luz. A amplitude complexa desses feixes são proporcionais às funções hipergeométricas confluentes, que denominamos modos hipergeométricos do segundo tipo (HyG-II). Demonstramos formalmente que um meio com um perfil hiperbólico de índice de refração pode gerar e suportar essa classe de feixes. Uma vez que esses modos são autofunções do momento angular orbital do fóton, concluímos que uma fibra ótica com este perfil de índice, em certas situações, poderia levar vantagem em relação a outras fibras com índice variável na capacidade de transmissão de dados.
102

Um estudo sobre o momentum angular total de estrelas com planetas

Santana, Juliana Cerqueira de 29 November 2011 (has links)
Made available in DSpace on 2014-12-17T15:15:00Z (GMT). No. of bitstreams: 1 JulianaCS_DISSERT.pdf: 3176095 bytes, checksum: 698fc04621ae821b481850e332892a95 (MD5) Previous issue date: 2011-11-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Since Michel Mayor and his student Didier Queloz s pioneer announcement, in 1995, of the existence of a planet orbiting the star 51 Peg, up to present date, 695 extrasolar planets orbiting stars of spectral type F, G, K and M have been discovered. A study on the behavior of the total angular momentum of the planetary systems known up to present date becomes relevant when we know that about 98% of the angular momentum of the solar system is associated with the planets, although they represent only 0.15 percent of the mass of the whole system. In this dissertation we study the behavior of stellar angular momentum, orbital angular momentum and total angular momentum in a sample of 282 stars harboring planets, including 40 multiple systems. We observed that planetary systems containing more than one known planet have both higher orbital angular momentum and total angular momentum compared to those who have only one planet. This analysis shows that multiplanet systems tend to have higher momenta, suggesting that the planets in such systems that contribute to the greater portion momenta have been found. Thus, planetary systems with lower values for the momenta represent the best candidates to the discovery of new planets / Desde o anuncio pioneiro de Michel Mayor e seu ent?o estudante Didier Queloz, em 1995, da exist?ncia de um planeta orbitando a estrela 51 Peg, at? a presente data, 695 planetas extrasolares foram descobertos, orbitando estrelas do tipo espectral F, G, K e M. Um estudo sobre o comportamento do momentum angular total dos sistemas planet?rios, conhecidos at? o momento, torna-se relevante quando conhecemos que cerca de 98% do momentum angular do Sistema Solar est? associado aos planetas, embora esses representem apenas 0,15% da massa de todo o Sistema. Na presente disserta??o de mestrado estudamos o comportamento do momentum angular estelar, do momentum angular orbital e do momentum angular total numa amostra de 282 estrelas, abrigando planetas, incluindo 40 sistemas multiplos. Observamos que os sistemas planet?rios contendo mais de 1 planeta conhecido possuem tanto momentum angular orbital quanto momentum angular total mais elevado, comparado ?queles sistemas que possuem apenas 1 planeta. Esta an?lise mostra que sistemas planet?rios m?ltiplos tendem a ter momenta mais elevado, sugerindo que em tais sistemas os planetas que contribuem com maior parcela para o momenta j? foram descobertos. Sendo assim, sistemas planet?rios com menores valores para o momenta representam melhores candidatos para a descoberta de novos planetas
103

Caractérisation des fragments de fission et développement du dispositif expérimental FALSTAFF / Fission fragment characterisation and development of the experimental setup FALSTAFF

Thulliez, Loïc 25 September 2017 (has links)
La fission nucléaire est le mécanisme de séparation d'un noyau lourd en deux noyaux appelés fragments de fission. Ces fragments excités émettent des neutrons et des gammas dits prompts pour rejoindre leur état fondamental ou métastable. L'énergie libérée lors de la fission est utilisée dans les centrales nucléaires pour fournir de l'électricité. La durée de vie et le contrôle des réacteurs nucléaires dépendent entre autres des observables de fission telles que les rendements en masse des fragments, la multiplicité et l'énergie des neutrons et des gammas prompts. La première partie de cette thèse est dédiée à l'étude du processus de désexcitation des fragments de fission avec le code de simulation Monte-Carlo FIFRELIN. Ce code, constitué de plusieurs modèles nucléaires permettant de décrire les fragments, prédit les propriétés (multiplicité, énergie) des particules promptes émises lors de la désexcitation. Lors de ce travail de thèse l'influence des modèles sur les prédictions du code a été étudiée. Les modèles étudiés sont ceux définissant le moment angulaire initial, la densité de niveaux et les fonctions de force gamma des fragments. Les résultats de ces études permettent d'identifier les modèles qui influencent significativement les prédictions du code et donc, de sélectionner la combinaison des modèles reproduisant le maximum d'observables et d'améliorer la description nucléaire des fragments. Ces études sont d'abord menées sur la fission spontanée du 252Cf pour laquelle de nombreuses données expérimentales existent ce qui permet de contraindre fortement les modèles. Des études sur la fission rapide (énergie des neutrons incidents de l'ordre du MeV) de 238U et 237Np sont ensuite réalisées. Elles sont motivées, entre autres, par le développement de nouveaux concepts de réacteurs rapides, dits de quatrième génération, permettant de réduire les quantités de déchets nucléaires et d'utiliser les réserves abondantes de 238U pour fournir de l'électricité. Les données expérimentales relatives à la fission rapide sont rares. De nouveaux dispositifs expérimentaux sont actuellement en développement afin d’étudier l’évolution des différentes observables de fission sur un large domaine en énergie d’excitation. Le dispositif FALSTAFF qui fait l'objet de la deuxième partie de cette thèse est l'un d'entre eux. Dans cette seconde partie les étapes de développement, d'optimisation et de caractérisation du premier bras du dispositif expérimental FALSTAFF sont présentées. Ce spectromètre, installé auprès de l'installation NFS (Neutrons For Science), permettra d'étudier la fission rapide en cinématique directe de nombreux actinides. La détection des deux fragments de fission en coïncidence permettra de caractériser leur énergie, leurs masses (avant et après évaporation des neutrons) et leur charge. La multiplicité des neutrons émis sera alors déterminée et nous renseignera sur le partage de l'énergie d’excitation entre les fragments. Les données mesurées serviront ultérieurement de données d'entrée au code FIFRELIN. La mesure de la vitesse des deux fragments en coïncidence (méthode 2V), avec des détecteurs de temps de vol MWPC-SeD donnent accès à la masse avant évaporation. Une chambre à ionisation axiale placée après ces détecteurs permet de mesurer l'énergie cinétique et le profil de perte d'énergie des fragments, ce qui permet de déterminer respectivement la masse après évaporation (méthode EV) et la charge nucléaire des fragments.La partie expérimentale de cette thèse est dédiée au développement des programmes de simulation et d'analyse des données, à la mise en place du système d'acquisition, à la caractérisation et à l'optimisation des détecteurs. Ce dernier point concerne essentiellement l'étude des performances de la chambre à ionisation axiale. / Nuclear fission is the process in which a heavy nucleus splits into two nuclei called fission fragments. These excited fragments emit prompt neutrons and gammas to reach their ground or a metastable state. The energy released during fission is used in nuclear power plants to provide electricity. The nuclear reactor lifespan and control depend partly on fission observables such as the fragment mass yields, the neutron and gamma multiplicity and energy. The first part of this thesis is dedicated to the study of the fission fragment de-excitation process with the FIFRELIN Monte-Carlo code. This code, containing many nuclear models describing the fragments, predicts the prompt particle properties (multiplicity, energy).During this PhD work the impact of different models on the code predictions was investigated. The models which are studied are those defining the initial angular momentum, the level density and the radiative strength function of fragments. These studies identified those nuclear properties that have a significant impact on the code predictions, and as a consequence permitted selection of the model combination suited to reproduce the maximum number of fission observables, and improving our understanding about the nuclear description of fission fragments. These studies are firstly performed on the spontaneous fission of 252Cf for which numerous experimental data are available allowing constraints to be set on the models. Studies on fast fission (incident neutron with an energy around MeV) of 238U and 237Np are then performed. They are motivated partly by the development of new fast reactor concepts, called Generation IV reactors, that will reduce the quantity of nuclear waste and burn the large amount of natural uranium to provide electricity. Experimental data concerning fast fission are scarce. As a consequence new experimental setups are currently under development. They will measure fission observables over a large excitation energy domain. One of them, called FALSTAFF, is the topic of the second part of this thesis. In the second part of this PhD thesis, the different steps concerning the development, the optimization and the characterization of the first arm of the FALSTAFF setup are presented. This spectrometer, placed at the NFS facility (Neutrons For Science), will study fast fission in direct kinematic for various actinides. The detection of both fragments in coincidence will allow characterization of their energy, their masses (before and after neutron evaporation) and their nuclear charge. The neutron multiplicity will be deduced and will provide information on the energy sharing between the fragments. This data will be later used as input for the FIFRELIN code. The velocity determination of both fragments (2V method), with MWPC-SeD time-of-flight detectors, will provide pre-neutron emission fragment masses. An axial ionization chamber, placed after those detectors, will measure the kinematic energy and the energy loss profile of fragments, which will provide respectively the post-neutron emission mass (EV method) and the nuclear charge. The experimental part of this thesis is dedicated to the development of simulation and data analysis software, the configuration of the data acquisition system, the characterization and the optimization of the detectors. This last item mainly concerns the axial ionization chamber.
104

Elliptical Vortex Beams Through Turbulent Atmosphere.

Narváez Castañeda, Emmanuel January 2020 (has links)
No description available.
105

Etudes à haute résolution angulaire de la cinématique des enveloppes proto-stellaires / High angular resolution studies of the kinematics of proto-stellar envelopes

Gaudel, Mathilde 27 November 2018 (has links)
Les étoiles se forment par effondrement gravitationnel de condensations pré-stellaires. Le jeune embryon stellaire (phase Classe 0) croît en masse par l'accrétion progressive de l'enveloppe de gaz et de poussières dans lequel il est enfoui. Par conservation du moment cinétique, si le moment du coeur pré-stellaire est totalement transféré à l'embryon pendant la phase d'accrétion, la force gravitationnelle ne peut contrer la force centrifuge et l'embryon se fragmente prématurément. Pour former une étoile comme notre Soleil, l'enveloppe en rotation doit nécessairement réduire son moment cinétique de 5 à 10 ordres de grandeur en l'évacuant ou en le redistribuant. L'un des principaux défis de la formation stellaire est de quantifier l'ampleur de ce "problème du moment cinétique" et d'identifier les mécanismes responsables de la redistribution du moment.L'objectif de cette thèse est d'étudier la cinématique des enveloppes proto-stellaires de Classe 0 afin d'établir leurs distributions de moment cinétique. Pour cela, j'ai utilisé des observations de raies moléculaires à haute résolution angulaire de l'Interféromètre du Plateau de Bure et du télescope de 30m de l'IRAM issues du large programme CALYPSO (Continuum and Lines in Young Protostellar Objects, PI : Ph. André) pour un échantillon de 12 proto-étoiles de Classe 0 à une distance d<400 pc. Cette analyse a permis de mesurer des mouvements de rotation différentielle et d'établir, pour la première fois, des distributions radiales du moment cinétique spécifique sur une grande gamme d'échelles (~50-10000 au) dans 11 des 12 enveloppes proto-stellaires de l'échantillon. Deux régimes distincts ont ainsi été mis en exergue: un profil constant à petites échelles (<1600 au) et une augmentation du moment avec le rayon aux grandes échelles (1600-10000 au).Le profil constant montre que la matière participant directement à la formation de l'étoile possède un moment cinétique spécifique (~5 10^-4 km/s pc, <1600 au) similaire à celui observé dans les petits disques entourant les étoiles T-Tauri.Les gradients de vitesse observés aux grandes échelles (>3000 au), historiquement utilisés pour mesurer la rotation des coeurs et quantifier le problème du moment cinétique, ne sont pas dus à la pure rotation des enveloppe proto-stellaires, mais sont dominés par d'autres mécanismes. Plusieurs scénarios sont donc discutés pour interpréter le changement de régime dans les profils de moment cinétique aux échelles >1600 au: une empreinte des conditions initiales de la phase pré-stellaire, un changement de mécanismes dominants (contre-rotation, transition effondrement-rotation) ou l'influence de la dynamique des filaments interstellaires (turbulence, effondrement, chocs) dans lesquels les proto-étoiles sont enfouies. / Stars form via the gravitational collapse of a pre-stellar condensation. The young stellar embryo (Class 0 phase) mass increases via the progressive accretion of the gaseous and dusty envelope within which it is buried. As a direct consequence of the angular momentum conservation, if the angular momentum of the pre-stellar core is totally transferred to the central embryo during the accretion phase, the gravitational force can not counteract the centrifugal force and the embryo fragments prematurely before reaching the main sequence. To form a star such as our Sun, the rotating envelope needs to reduce its angular momentum by 5 to 10 orders of magnitude by ejecting or redistributing it. One of the main challenges of stellar formation is to quantify the amplitude of this "angular momentum problem" and identify the mechanisms responsible for the angular momentum redistribution.The goal of this PhD thesis is to study the kinematics of Class 0 protostellar envelopes in order to probe the distribution of their angular momentum. To do this, I used high-resolution observations of molecular lines with the Plateau de Bure Interferometer and the 30m telescope at IRAM taken as part of the large programme CALYPSO (Continuum and Lines in Young Protostellar Objects, PI : Ph. André). The sample gathers 12 Class 0 protostars with distances d<400 pc. This analysis allows to measure differential rotation motions and provides, for the first time in a large sample, robust constraints on the radial distributions of specific angular momentum in a large range of scales (~50-10000 au) for 11 of the 12 protostellar envelopes targeted in the sample. Two distinct regimes are revealed: a constant profile at small scales (<1600 au) and an increasing of the angular momentum at larger radii (1600-10000 au).The constant profile shows that the specific angular momentum (~5 10-4 km/s pc, <1600 au) of the material directly involved in the star formation is similar to the value observed in the small disks surrounding the T-Tauri stars.Velocity gradients observed on large scales (>3000 au) - that are historically used to measure the rotation of the core and quantify the angular momentum problem - are not due to pure envelope rotation but can be dominated by other mechanisms. I discuss several scenarios in order to interpret this change of regime in the angular momentum profiles at scales >1600 au: the imprints of the initial conditions of the pre-stellar phase, a change of dominant mechanisms (counter-rotation, transition between infall and rotation) or the influence of the interstellar filament dynamics (turbulence, collapse, shocks) within which protostars are buried.
106

Spatiotemporal Manipulation of Optical Vortices

Zang, Yimin January 2021 (has links)
No description available.
107

Derivation of the angular momentum of primary fission fragments from isomeric yield ratio by TALYS using Python

Bagher Nori, Mohammad January 2021 (has links)
The general fission process is well known and is applied in nuclear power plants all over the world. However many properties of fission fragments are still not well understood. The angular momentum distribution of fission fragments is an important property to gain a better understanding of the fission process, and that can be derived indirectly from isomeric yield ratios. The goal of this project has been to develop a script in Python that runs the nuclear reaction code TALYS with the Total Monte Carlo method to calculate the isomeric yield ratio. The script generates a matrix consisting of excitation energies and angular momenta that is provided to TALYS. One matrix corresponds to one calculation of the isomeric ratio. Thus, the dependency of the isomeric yield ratio on these matrices can be observed. After looking into the matrices, the dependencies of the isomeric yield ratios on the excitation energies and the angular momentum distribution are observed. In this project, the calculated isomeric yield ratios are compared with the experimental value obtained from an experiment conducted in August of 2019 at the IGISOL-JYFLTRAP facility in Jyväskylä, Finland. It is worth mentioning that, fission system is of Uranium-238 which was induced by a proton beam at an energy of 25 MeV. The dependency of the isomeric yield ratio (IYR) on the angular momentum and the excitation energy has been investigated. However, it has proved more difficult than expected, to deduce an estimation for the angular momentum distribution. Another finding of this project is that the two codes used, GEF and TALYS sometimes produce inconstant results.
108

Tailoring quantum entanglement of orbital angular momentum

McLaren, Melanie 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: High-dimensional quantum entanglement offers an increase in information capacity per photon; a highly desirable property for quantum information processes such as quantum communication, computation and teleportation. As the orbital angular momentum (OAM) modes of light span an infinite-dimensional Hilbert space, they have become frontrunners in achieving entanglement in higher dimensions. In light of this, we investigate the potential of OAM entanglement of photons by controlling the parameters in both the generation and measurement systems. We show the experimental procedures and apparatus involved in generating and measuring entangled photons in two-dimensions. We verify important quantum tests such as the Einstein, Podolsky and Rosen (EPR) paradox using OAM and angle correlations, as well as a violation of a Bell-type inequality. By performing a full state tomography, we characterise our quantum state and show we have a pure, highly entangled quantum state. We demonstrate that this method can be extended to higher dimensions. The experimental techniques used to generate and measure OAM entanglement place an upper bound on the number of accessible OAM modes. As such, we investigate new methods in which to increase the spiral bandwidth of our generated quantum state. We alter the shape of the pump beam in spontaneous parametric down-conversion and demonstrate an effect on both OAM and angle correlations. We also made changes to the measurement scheme by projecting the photon pairs into the Bessel-Gaussian (BG) basis and demonstrate entanglement in this basis. We show that this method allows the measured spiral bandwidth to be optimised by simply varying the continuous radial parameter of the BG modes. We demonstrate that BG modes can be entangled in higher dimensions compared with the commonly used helical modes by calculating and comparing the linear entropy and fidelity for both modes. We also show that quantum entanglement can be accurately simulated using classical light using back-projection, which allows the study of projective measurements and predicts the strength of the coincidence correlations in an entanglement experiment. Finally, we make use of each of the techniques to demonstrate the effect of a perturbation on OAM entanglement measured in the BG basis. We investigate the self-healing property of BG beams and show that the classical property is translated to the quantum regime. By calculating the concurrence, we see that measured entanglement recovers after encountering an obstruction. / AFRIKAANSE OPSOMMING: Hoë-dimensionele kwantumverstrengeldheid bied ’n toename in inligtingskapasiteit per foton. Hierdie is ’n hoogs wenslike eienskap vir kwantum inligting prosesse soos kwantum kommunikasie, berekening en teleportasie. Omdat die orbitale hoekmomentum (OAM) modusse van lig ’n oneindig dimensionele Hilbertruimte beslaan, het dit voorlopers geword in die verkryging van verstrengeling in hoër dimensies. In die lig hiervan, ondersoek ons die potensiaal van OAM verstrengeling van fotone deur die parameters in beide die generering en meting stelsels te beheer. Ons toon die eksperimentele prosedures en apparaat wat betrokke is by die generering en die meet van verstrengelde fotone in twee dimensies. Ons verifieer kwantumtoetse, soos die Einstein, Podolsky en Rosen (EPR) paradoks vir OAM en die hoekkorrelasies, sowel as ’n skending van ’n Bell-tipe ongelykheid. Deur middel van ’n volledige toestand tomografie, karakteriseer ons die kwantum toestand en wys ons dat dit ’n suiwer, hoogs verstrengel kwantum toestand is. Ons toon ook dat hierdie metode uitgebrei kan word na hoër dimensies. Die eksperimentele tegnieke wat tydens die generasie en meet van OAM verstrengeling gebruik is, plaas ’n bogrens op die aantal toeganklik OAM modusse. Dus ondersoek ons nuwe metodes om die spiraal bandwydte van ons gegenereerde kwantum toestand te verhoog. Ons verander die vorm van die pomp bundel in spontane parametriese af-omskakeling en demonstreer die uitwerking daarvan op beide OAM en die hoekkorrelasies. Ons het ook veranderinge aan die meting skema gemaak deur die foton pare op die Bessel-Gauss (BG) basis te projekteer. Ons wys dat hierdie metode die gemeetde spiraal bandwydte kan optimeer deur eenvoudig die kontinue radiale parameter van die BG modes te verander. Ons demonstreer dat BG modusse verstrengel kan word in hoër dimensies as die heliese modusse, wat algemeen gebruik word, deur berekeninge te maak en te vergelyk met lineêre entropie en vir beide modusse. Ons wys ook dat kwantumverstrengling akkuraat nageboots kan word, met behulp van die klassieke lig terug-projeksie, wat die studie van projeksie metings toelaat en voorspel die krag van die saamval korrelasies in ’n verstrengeling eksperiment. Ten slotte, gebruik ons elk van die tegnieke om die effek van ’n storing op OAM verstrengling wat in die BG basis gemeet is, te demonstreer. Ons ondersoek die self-genesingseienskap van BG bundels en wys dat die klassieke eienskap vertaal na die kwantum-gebied. Deur die berekening van die konkurrensie (concurrence), sien ons dat die gemeetde verstrengeling herstel word nadat ’n obstruksie ondervind is.
109

Stark deceleration and reactivity of polyatomic molecules and ions at low temperatures

Harper, Lee D. January 2013 (has links)
This thesis describes the development of a new experimental technique for studying tunable-collision-energy, quantum state-selected, low-temperature ion-molecule reactions. This has been achieved through the combination of a Stark decelerator for neutral dipolar molecules, and a linear Paul ion trap. The Stark deceleration process for ND<sub>3</sub> was examined in detail, through the analysis of experimental data in combination with newly written molecular dynamics simulation programs. In order to prepare a sample of molecules appropriate for collision studies, additional beamline components were introduced after the decelerator. These components were: two hexapoles, to provide transverse focussing, maximising the molecular density; a molecular buncher, providing increased longitudinal velocity resolution; and a fast-opening shutter, to separate decelerated molecules from undecelerated molecules. The sympathetic-cooling of Xe<sup>+</sup> ions and ND<sup>+</sup><sub>3</sub> ions by laser-cooled, Coulomb crystallised <sup>40</sup>Ca<sup>+</sup> ions with the ion trap was also studied. In particular, the stable trapping of Xe<sup>+</sup> was demonstrated for the first time, and the experimental developments that led to this are discussed. The work in this thesis represents significant progress towards studying the reaction of tunable-energy ND<sub>3</sub> in the |j,mk> = |1,−1> quantum state with cold Xe<sup>+</sup> ions. Ion-molecule reactions utilising ND<sub>3</sub> molecules electrostatically guided through the Stark decelerator were performed. It was observed that the main source of error in these experiments was in the calculation of the initial number of Xe<sup>+</sup> ions that had been sympathetically cooled into the Coulomb crystal. The sensitivity of the crystal morphology to the number of Xe<sup>+</sup> ions was evaluated using molecular dynamics simulations. Strategies have been developed to reduce this uncertainty in future studies. In addition to experimental work, the theory of low temperature ion-molecule reactions has been developed further. The temperature at which classical and quantum mechanical calculations diverge due to purely statistical effects has been investigated using different model intermolecular potentials, for closed-shell and open-shell species, and in the ground and rotationally excited states. From the results of these calculations, several promising candidate reactions have been suggested that might exhibit statistical quantum behaviour at experimentally achievable temperatures.
110

Bell inequalities with Orbital Angular Momentum of Light / Inégalités de Bell avec le Moment Angulaire Orbital de la lumière

Vannier Dos Santos Borges, Carolina 08 October 2012 (has links)
Dans une première partie introductive, nous rappelons la description théorique de la propagation de faisceaux optiques en terme des modes solutions de l'équation de propagation dans l'approximation paraxialle. Dans ce cadre, nous présentons les notions de moment cinétique transporté par les faisceaux lumineux, et de sa décomposition en moment cinétique intrinsèque (ou spin) et en moment angulaire.La seconde partie est consacrée au codage de l'information dans les degrés de libertés de polarisation et de modes transverses des faisceaux optiques. Les modes spin-orbites sont définis et un dispositif expérimental optique pour produire ces modes est présenté. Les modes spin-orbites sont alors exploités pour implémenter un protocole de distribution de clés BB84 ne nécessitant pas le partage à priori d'une base de référence.Dans une troisième partie, nous proposons un critère de type inégalité de Bell, qui constitue une condition suffisante pour caractériser la non-séparabilité en spin-orbite d'un faisceau optique classique. Nous montrons ensuite que la notion de modes spin-orbite séparable ou non-séparable constitue une analogie pertinente avec la notion d'intrication d'états quantiques et permet l'étude de certaines de ses propriétés fondamentales. Enfin, une implémentation expérimentale de cette simulation de tests de Bell avec des faisceaux optiques classiques est présentée, ainsi que sa description détaillée dans le cadre de l'optique quantique.Dans une dernière partie, nous nous intéressons à des inégalités de Bell, pour des états quantiques de systèmes quantiques à deux parties, qui sont caractérisées chacune par une variable continue de type angulaire (périodique). Nous montrons comment détecter la non-localité sur ce type de système, avec des inégalités qui sont similaires aux inégalités CHSH; inégalités qui avaient été développées originellement pour des systèmes de type spin 1/2. Nos inégalités, sont construites à partir de la mesure de la corrélation de fonctions angulaires. Nous montrons qu'elles sont en fait la superposition continue d'inégalités CHSH de type spin 1/2. Nous envisageons une possible implémentation expérimentale, où les corrélations mesurées sont les corrélations angulaires du profil transverse des photons intriqués. / We shall present a theoretical description of paraxial beams, showing the propagation modes that arise from the solution of the paraxial equation in free space. We then discuss the angular momentum carried by light beams, with its decomposition in spin and orbital angular momentum and its quantization. We present the polarization and transverse modes of a beam as potential degrees of freedom to encode information. We define the Spin-Orbit modes and explain the experimental methods to produce such modes. We then apply the Spin-Orbit modes to perform a BB84 quantum key distribution protocol without a shared reference frame.We propose a Bell-like inequality criterion as a sufficient condition for the spin-orbit non-separability of a classical laser beam. We show that the notion of separable and non-separable spin-orbit modes in classical optics builds a useful analogy with entangled quantum states, allowing for the study of some of their important mathematical properties. We present a detailed quantum optical description of the experiment in which a comprehensive range of quantum states are considered.Following the study of Bell's inequalities we consider bipartite quantum systems characterized by a continuous angular variable θ. We show how to reveal non-locality on this type of system using inequalities similar to CHSH ones, originally derived for bipartite spin 1/2 like systems. Such inequalities involve correlated measurement of continuous angular functions and are equivalent to the continuous superposition of CHSH inequalities acting on two-dimensional subspaces of the infinite dimensional Hilbert space. As an example, we discuss in detail one application of our results, which consists in measuring orientation correlations on the transverse profile of entangled photons.

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