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Wu, Biao. "Bose-Einstein condensation of dilute atomic gases." Access restricted to users with UT Austin EID, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3037026.
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Ozdemir, Sevilay. "Bose-einstein Condensation At Lower Dimensions." Master's thesis, METU, 2004. http://etd.lib.metu.edu/upload/755959/index.pdf.
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In this thesis, the properties of the Bose-Einstein condensation (BEC) in low dimensions are reviewed. Three dimensional weakly interacting Bose systems are examined by the variational method. The effects of both the attractive and the repulsive interatomic forces are studied. Thomas-Fermi approximation is applied to find the ground state energy and the chemical potential. The occurrence of the BEC in low dimensional systems, is studied for ideal gases confined by both harmonic and power-law potentials. The properties of BEC in highly anisotropic trap are investigated and the conditions for reduced dimensionality are derived.
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Schmidutz, Tobias Fabian. "Studies of a homogeneous Bose gas." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708544.
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Gotlibovych, Igor. "Degenerate Bose gases in a uniform potential." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708187.
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Jackson, Brian. "Vortices in trapped Bose-Einstein condensates." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4241/.
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In this thesis we solve the Gross-Pitaevskii equation numerically in order to model the response of trapped Bose-Einstein condensed gases to perturbations by electromagnetic fields. First, we simulate output coupling of pulses from the condensate and compare our results to experiments. The excitation and separation of eigen-modes on flow through a constriction is also studied. We then move on to the main theme of this thesis: the important subject of quantised vortices in Bose condensates, and the relation between Bose-Einstein condensation and superfluidity. We propose methods of producing vortex pairs and rings by controlled motion of objects. Full three-dimensional simulations under realistic experimental conditions are performed in order to test the validity of these ideas. We link vortex formation to drag forces on the object, which in turn is connected with energy transfer to the condensate. We therefore argue that vortex formation by moving objects is intimately related to the onset of dissipation in superfluids. We discuss this idea in the context of a recent experiment, using simulations to provide evidence of vortex formation in the experimental scenario. Superfluidity is also manifest in the property of persistent currents, which is linked to vortex stability and dynamics. We simulate vortex line and ring motion, and find in both cases precessional motion and thermodynamic instability to dissipation. Strictly speaking, the Gross-Pitaevskii equation is valid only for temperatures far below the BEG transition. We end the thesis by describing a simple finite- temperature model to describe mean-field coupling between condensed and non- condensed components of the gas. We show that our hybrid Monte-Carlo/FFT technique can describe damping of the lowest energy excitations of the system. Extensions to this model and future research directions are discussed in the conclusion.
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Campbell, Robert Lorne Dugald. "Thermodynamic properties of a Bose gas with tuneable interactions." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610631.
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Cofler, Enrico. "Teoria del condensato di Bose-Einstein." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14515/.
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Questo lavoro ripercorre gli aspetti principali della teoria del condensato di Bose-Einstein, utilizzando nozioni di fisica statistica, meccanica quantistica non relativistica e idrodinamica. Nella prima parte si ricava dalla statistica di Bose il fenomeno della condensazione, ovvero una transizione nel sistema che porta a un’occupazione macroscopica del livello energetico. Si discutono anche alcuni fenomeni fisici caratteristici che emergono da una prima osservazione del condensato in una trappola con potenziale armonico anisotropo. Dopo aver introdotto gli urti tra i bosoni, si calcola, mediante la teoria di campo medio, l’equazione di Gross-Pitaevskii, soddisfatta dalla funzione d’onda del condensato. Sfruttando il calcolo variazionale, è possibile inoltre valutare l’importanza del termine energetico di interazione e dell’energia cinetica, e introdurre opportune approssimazioni alla funzione d’onda a seconda delle condizioni fisiche in cui si realizza il condensato. Nell’ultimo capitolo si considera la dinamica del condensato generalizzando l’equazione di Gross-Pitaevskii al caso dipendente dal tempo. In particolare, sfruttando alcune nozioni della teoria di Bogoliubov, si mettono in luce le connessioni tra la teoria dello stato condensato e il fenomeno della superfluidità.
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Standen, Guy Benjamin. "The charged base gas." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388655.
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Challis, Katharine Jane, and n/a. "Bragg scattering of a solitary-wave condensate and of a Cooper paired Fermi gas." University of Otago. Department of Physics, 2006. http://adt.otago.ac.nz./public/adt-NZDU20061127.160615.
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In this thesis we develop Bragg scattering as a tool for probing and manipulating ultra-cold atoms. Our approach is based on a mean-field treatment of degenerate quantum gases. Bose-Einstein condensates are described by the Gross-Pitaevskii equation and degenerate Fermi gases are described by the Bogoliubov-de-Gennes equations. Our work is presented in three inter-related topics.
In Part I we investigate Bose-Einstein condensation in a time-averaged orbiting potential trap by deriving solitary-wave dynamical eigenstates of the system. We invoke the quadratic average approximation in which the dynamic effects of the time-dependent potential can be described simply, even when accounting for atomic collisions. By deriving the transformation to the translating frame, dynamical eigenstates of the system are defined and those states are solitary-wave solutions in the laboratory frame, with a particular circular centre-of-mass motion independent of the strength of the collisional interactions. Our treatment in the translating frame is more general than previous treatments that use the rotating frame to define system eigenstates, as the use of the rotating frame restricts eigenstates to those that are cylindrically symmetric about their centre of mass.
In Part II we describe Bragg spectroscopy of a condensate with solitary-wave motion. Our approach is based on a momentum space two-bin approximation, derived by Blakie et al. [Journal of Physics B 33:3961, 2000] to describe Bragg scattering of a stationary condensate. To provide an analytic treatment of Bragg scattering of a solitary-wave condensate we use the translating frame, in which the time dependence of the system is described entirely by a time-dependent optical potential. We derive a simplified treatment of the two-bin approximation that provides a physical interpretation of the Bragg spectrum of a solitary-wave condensate. Our methods are applied to Bragg spectroscopy of a condensate in a time-averaged orbiting potential trap, which accelerates as a solitary wave as derived in Part I. The time-averaged orbiting potential trap system is ideal for testing our approximate analytic methods because the micromotion velocity is large compared to the condensate momentum width.
In Part III we present a theoretical treatment of Bragg scattering of an ultra-cold Fermi gas. We give the first non-perturbative numerical calculations of the dynamic behaviour of a degenerate Fermi gas subjected to an optical Bragg grating. We observe first order Bragg scattering, familiar from Bragg scattering of stationary Bose-Einstein condensates, and at lower Bragg frequencies we predict scattering of Cooper pairs into a correlated spherical shell of atoms. Correlated-pair scattering is associated with formation of a grating in the pair potential. We give an analytic treatment of Bragg scattering of a homogeneous Fermi gas, and develop a model that reproduces the key features of the correlated-pair Bragg scattering. We discuss the effect of either a trapping potential or finite temperature on the correlated-pair Bragg scattering.
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Brtka, Marijana [UNESP]. "Oscilações não-lineares em condensados de Bose-Einstein." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/102506.
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brtka_m_dr_ift.pdf: 1102252 bytes, checksum: 1a7b66f943a95b6ff94475b02062691c (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Estudamos as oscilações não-lineares de um condensado de Bose-Einstein em três dimensões numa armadilha com simetria esférica e com comprimento de espalhamento periódico no tempo. Usamos o método variacional dependente do tempo e deduzimos a equação para a largura do condensado. A partir desta equação, analisaremos as características das ressonâncias não-lineares e o efeito de bi-estabilidade em oscilações da largura do condensado. Previsões teóricas são confirmadas pelas simulações numéricas da equação de Gross-Pitaevskii.
Nonlinear oscillations of a 3D radial symmetric Bose-Einstein condensate (BEC) under periodic variation in time of the atomic scattering length have been studied. The time-dependent variational approach is used for analysis of the characteristics of nonlinear resonances in the oscillations of the condensate. The bistability in oscillations of the BEC width is investigated. Predictions of the theory are confirmed by numerical simulations of the full Gross-Pitaevskii equation.
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Desbuquois, Rémi. "Thermal and superfluid properties of the two-dimensional Bose gas." Paris 6, 2013. http://www.theses.fr/2013PA066068.
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The physical properties of a homogeneous system at the thermodynamic equilibrium are strongly constrained by its dimensionality. In this respect, the two dimensional Bose gas constitutes a particularly interesting system: while it is impossible to observe a long range order at non-zero temperatures, there exists nevertheless a phase transition to a superfluid state at low temperatures. Furthermore, owing to the reduced dimensionality, the equation of state of the weakly interacting two-dimensional Bose gas is scale invariant. In this thesis, we present an experimental study of the two-dimensional Bose gas. We measure its equation of state with two different methods, and find a good agreement with analytic and numerical predictions. These results confirm as well the scale invariance of the system. Furthermore, one of the methods allows for a determination of the equation of state with a single adjustable parameter. We then characterize the superfluid response of the system. , by showing evidence for a dissipationless response of the system to a moving perturbation. Finally, we analyze the fluctuations dynamics of the 2D Bose gas, which confirms both the suppression of density fluctuations in the superfluid phase, and the dominating contribution of phonons to the phase fluctuationsLes propriétés physiques d'un système homogène à l'équilibre thermodynamique sont fortement contraintes par sa dimensionnalité. Le gaz de Bose à deux dimensions est un système particulier de ce point de vue : bien que l'établissement d'un ordre à longue portée soit impossible à température non-nulle, il existe néanmoins une transition de phase vers un état superfluide à basse température. De plus, la dimensionnalité réduite du système rend son équation d'état invariante par changement d'échelle pour de faibles interactions atomiques répulsives. Dans ce manuscrit de thèse, nous présentons une étude expérimentale du gaz de Bose à deux dimensions. Nous mesurons son équation d'état de deux méthodes différentes, et trouvons un résultat en bon accord avec les prédictions analytiques et numériques. Ces résultats ont également permis de confirmer l'invariance d'échelle du système. De plus, l'une des méthodes ne nécessite qu'un seul paramètre ajustable pour la mesure de l'équation d'état. Nous présentons ensuite une mesure locale du caractère superfluide du gaz. A cet effet, nous avons mis en évidence l'absence de dissipation lors de la perturbation du système par un obstacle en mouvement. Enfin, nous effectuons une analyse des fluctuations du gaz de Bose 2D, qui a permis de confirmer la suppression des fluctuations de densité dans la phase superfluide, ainsi que le rôle dominant joué par les phonons dans les fluctuations de phase
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Fritsch, Amilson Rogelso. "Thermodynamics of a Bose gas: Sound velocity from global variables and equivalence with other approaches." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-13032017-144758/.
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In this thesis we present some studies that were done in a trapped 87Rb Bose-Einstein condensate using the thermodynamic global variables. We have measured the global sound velocity by studying the variation of the total number of trapped atoms as a function of temperature. This method allowed us to determine the contribution of thermal and BEC components at each temperature. In order to study the sound velocity in each component, we treated both fluids as they were completely independent and we found great similarity with a published work. In addition, we analyze theoretically the validity of the global variables by comparing this approach with other methods. The specific heat for an ideal gas was evaluated using the global variables and by using the usual statistical approach found in textbooks. After finding the same result for both methods, we used the simplicity to implement the interaction in the global approach, to study the variation in the specific heat when the interactions are taken into account. The last comparison was done between global variables and the local density approximation. We have obtained that, for the isothermal compressibility and a equation of state, both methods provide equivalent results.Nesta tese descrevemos estudos que foram feitos em um Condensado de Bose-Einstein de 87Rb usando variáveis termodinâmicas globais. A velocidade do som foi medida através de variações do número de átomos aprisionados em função da temperatura. Com este método fomos capazes de determinar qual a contribuição da componente térmica e do condensado em cada temperatura. Com o objetivo de estudar a velocidade do som em cada componente, analisamos ambas componentes como se elas fossem totalmente independentes, e encontramos grande similaridade com outro trabalho publicado. Adicionalmente, um estudo teórico foi feito para analisar a validade das variáveis globais comparando com outros métodos. O calor específico para um gás ideal foi calculado usando as variáveis globais e também usando o tratamento estatístico convencional encontrado em livros-texto. Depois de encontrar os mesmos resultados com os dois métodos, usamos a facilidade que temos em considerar as interações entre os átomos usando as variáveis globais, e estudamos a variação no calor específico quando estas interações são consideradas. Em um último estudo, comparamos as variáveis globais com o método de aproximação da densidade local. Para a compressibilidade isotérmica e para uma equação de estado obtemos resultados equivalentes com os dois métodos.
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Rafler, Mathias. "Martin-Dynkin Boundaries of the Bose Gas." Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2011/5166/.
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The Ginibre gas is a Poisson point process dened on a space of loops related to the Feynman-Kac representation of the ideal Bose gas. Here we study thermodynamic limits of dierent ensembles via Martin-Dynkin boundary technique and show, in which way innitely long loops occur. This effect is the so-called Bose-Einstein condensation.
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Buggle, Christian. "Collective and collisional properties of the Rubidium quantum gas." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2005. http://dare.uva.nl/document/78220.
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Hoang, Thai Minh. "Quantum control of a many-body system in a spin-1 Bose-Einstein condensate." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50358.
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Ultracold atoms provide a powerful tool for studying quantum control of interacting many-body systems with well-characterized and controllable Hamiltonians. In this thesis, we demonstrate quantum control of a many-body system consisting of a ferromagnetic spin-1 Bose-Einstein condensate (BEC). By tuning the Hamiltonian of the system, we can generate either a phase space with an unstable hyperbolic fixed point or a phase space with an elliptical fixed point. A classical pendulum with a stable oscillation about the "down" position and an inverted pendulum with unstable non-equilibrium dynamics about the "up" position are classical analogs of the quantum spin dynamics we investigate in this thesis. In one experiment, we dynamically stabilize the system about an unstable hyperbolic fixed point, which is similar to stabilizing an inverted pendulum. In a second experiment, we parametrically excite the system by modulating the quadratic Zeeman energy. In addition, we demonstrate rectifier phase control as a new method to manipulate the quantum states of the many-body system. This is similar to parametric excitation and manipulation of the oscillation angle of a classical pendulum. These experiments demonstrate the ability to control a quantum system realized in a spinor BEC, and they also can be applied to other quantum systems. In addition, we extend our studies to atoms above the Bose-Einstein transition temperature, and we present results on thermal spin relaxation processes and equilibrium spin populations.
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Chomaz, Lauriane. "Cohérence et Superfluidité de gaz de Bose en dimension réduite : des pièges harmoniques aux fluides uniformes." Thesis, Paris, Ecole normale supérieure, 2014. http://www.theses.fr/2014ENSU0013/document.
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La dimensionnalité d’un système affecte fortement ses propriétés physiques ; les transitions de phasequi s’y déroulent ainsi que le type d’ordre qui y apparaît dépendent de la dimension. Dans les systèmesde basse dimension, la cohérence s’avère plus difficile à établir car les fluctuations thermiques etquantiques y jouent un rôle plus important. Le fluide de Bose à deux dimensions est particulièrementintéressant car, même si un ordre total est exclu, un ordre résiduel à « quasi-longue » portée s’établit àbasse température. Deux ingrédients ont un effet significatif sur l’état du système : (i) la taille finie d’unsystème réel permet de retrouver une occupation macroscopique d’un état à une particule ; (ii) les interactionsentre particules conduisent à l’apparition d’un type non-conventionnel de transition de phasevers un état superfluide.Dans cette thèse, nous présentons une étude expérimentale du gaz de Bose bidimensionnel (2D) utilisantdeux types de paysages énergétiques pour piéger nos atomes. Dans la première partie, nous utilisonsla dépendance spatiale de certaines propriétés locales d’un gaz inhomogène pour caractériser l’étatdu système homogène équivalent. Nous extrayons son équation d’état des profils de densité et noustestons son comportement superfluide en mesurant le chauffage induit par le mouvement d’une perturbationlocale. Dans la deuxième partie, nous observons et caractérisons l’émergence d’une cohérencede phase étendue dans un gaz 2D homogène, en particulier via le passage de trois dimensions à deux(croisement dimensionnel). Nous étudions l’établissement dynamique de la cohérence par un passagerapide du croisement dimensionnel et nous observons des défauts topologiques dans l’état superfluidefinal. Nous comparons nos résultats avec les prédictions du mécanisme de Kibble–ZurekThe dimensionality of a system strongly affects its physical properties; the phase transitions that takeplace and the type of order that arises depend on the dimension. In low dimensional systems phasecoherence proves more difficult to achieve as both thermal and quantum fluctuations play a strongerrole. The two-dimensional Bose fluid is of particular interest as even if full order is precluded, a residual"quasi-long" range order arises at low temperatures. Then two ingredients have a significant effecton the state of the system: (i) the finite size of a real system enables one to recover of a macroscopicoccupation of a single-particle state; (ii) the interactions between particles lead to the emergence of anon-conventional type of phase transition toward a superfluid state.In this thesis, we present an experimental study of the two-dimensional (2D) Bose gas using two differentenergy landscapes to trap our atoms. In the first part, we use the spatial dependence of somelocal properties of an inhomogeneous gas to characterize the state of the equivalent homogeneous system.We extract its equation of state with a high accuracy from the gas density profiles and test itssuperfluid behavior by measuring the heating induced by a moving local perturbation. In the secondpart, we observe and characterize the emergence of an extended phase coherence in a 2D homogeneousgas in particular via a 3D-to-2D dimensional crossover. We investigate the dynamical establishment ofthe coherence via a rapid crossing of the dimensional crossover and observe topological defects in thefinal superfluid state. We compare our findings with the predictions for the Kibble–Zurek mechanism
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Kerl, John R. "Critical behavior for the model of random spatial permutations." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/193647.
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We examine a phase transition in a model of random spatial permutations which originates in a study of the interacting Bose gas. Permutations are weighted according to point positions; the low-temperature onset of the appearance of arbitrarily long cycles is connected to the phase transition of Bose-Einstein condensates. In our simplified model, point positions are held fixed on the fully occupied cubic lattice and interactions are expressed as Ewens-type weights on cycle lengths of permutations. The critical temperature of the transition to long cycles depends on an interaction-strength parameter α. For weak interactions, the shift in critical temperature is expected to be linear in α with constant of linearity c. Using Markov chain Monte Carlo methods and finite-size scaling, we find c = 0.618 ± 0.086. This finding matches a similar analytical result of Ueltschi and Betz. We also examine the mean longest cycle length as a fraction of the number of sites in long cycles, recovering an earlier result of Shepp and Lloyd for non-spatial permutations. The plan of this paper is as follows. We begin with a non-technical discussion of the historical context of the project, along with a mention of alternative approaches. Relevant previous works are cited, thus annotating the bibliography. The random-cycle approach to the BEC problem requires a model of spatial permutations. This model it is of its own probabilistic interest; it is developed mathematically, without reference to the Bose gas. Our Markov-chain Monte Carlo algorithms for sampling from the random-cycle distribution - the swap-only, swap-and-reverse, band-update, and worm algorithms - are presented, compared, and contrasted. Finite-size scaling techniques are used to obtain information about infinite-volume quantities from finite-volume computational data.
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Corman, Laura. "The two-dimensional Bose Gas in box potentials." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE014/document.
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Les gaz quantiques atomiques constituent un outil de choix pour étudier la physique à N corps grâce à leurs nombreux paramètres de contrôle. Ils offrent la possibilité d’explorer la physique en basse dimension, modifiée par rapport au cas à trois dimensions (3D) à cause du rôle accru des fluctuations. Dans ce travail, nous étudions le gaz de Bose à deux dimensions (2D) avec un confine-ment original dans le plan atomique, uniforme et de motif arbitraire. Ces gaz2D et uniformes, développés sur un montage existant, ont été installés sur un nouveau montage grâce à des potentiels optiques polyvalents.Nous présentons une série d’expériences exploitant cette géométrie flexible.D’abord, nous étudions le comportement statique et dynamique d’un gaz uni-forme lors de la transition d’un état 3D normal vers un état 2D superfluide.Nous observons l’établissement de la cohérence de phase dans un gaz à l’équilibre puis nous montrons l’apparition après une trempe de défauts topologiques dont le nombre est comparé à la prédiction de Kibble-Zurek. Ensuite, nous étudions grâce au nouveau montage les effets collectifs dans l’interaction lumière-matière, où les propriétés de résonance d’un nuage d’atomes dense sont fortement modifiées par rapport à celles d’un atome unique. Enfin, nous proposons deux protocoles pour le nouveau montage. Le premier permet d’évaporer de manière uniforme un gaz 2D grâce au réseau incliné du confinement à 2D. Le second propose de produire des supercourants de manière déterministe dans des pièges en anneaux, soit par condensation dans un champ de jauge, soit en réalisant une pompe à vortex topologiqueDegenerate atomic gases are a versatile tool to study many-body physics. They offer the possibility to explore low-dimension physics, which strongly differs from the three dimensional (3D) case due to the enhanced role of fluctuations. In this work, we study degenerate 2D Bose gases whose original in-plane confinement is uniform and of arbitrary shape. These 2D uniform traps, which we first developed on an existing set-up, were subsequently implemented on a newset-up using versatile optical potentials. We present a series of experiments that take advantage of this flexible geometry. First, we study the static and dynamic behaviours of a uniform gas at the transition between a 3D normal and a 2D superfluid state. We observe the establishement of extended phase coherence, followed, as the gas is quench cooled, by the apparition of topological defects whose scaling is compared to the Kibble-Zurek prediction. Second, we present the first results of the new set-up : we investigate collective effects in light-matter interactions, where the resonance properties of a dense ensemble of atoms are strongly modified with respect to the single atom ones. Last, we develop two experimental proposals for the new set-up. The first one studies how a 2D gas can be uniformly evaporated using the tilted lattice providing the 2D confinement. In the second one, we propose to produce su-percurrents in a deterministic way in ring-shaped traps either by condensing inan artificial gauge field or by implementing a topological vortex pump
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Briosne, frejaville Clémence. "Transport et confinement optique d'atomes de strontium pour une expérience de microscope à gaz quantique." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP037.
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Les travaux présentés dans ce manuscrit de thèse portent sur la construction d’un nouveau dispositif pour atomes froids de strontium 84. Les expériences réalisées sur ce montage porteront sur la dynamique de relaxation de gaz quantiques hors équilibre. Cette dynamique est étudiée pour des gaz bidimensionnels sur réseau. Ce manuscrit de thèse s'attache à décrire la conception des systèmes optiques utilisés pour piéger et manipuler les gaz lors des expériences. En particulier, le montage optique utilisé pour le transport des atomes entre deux positions de l'enceinte à vide est présenté. La solution choisie pour la réalisation du piège bidimensionnel est elle aussi détaillée. Enfin, un microscope à gaz quantiques est mis en place afin de mesurer in situ les fonctions de corrélation spatiales à partir de la répartition des atomes dans le piège bidimensionnel. Une caractérisation du microscope est présentée dans ce manuscrit. Bien que la conception des différents systèmes optiques soit terminée dans sa première version, il nous reste quelques étapes de construction avant d'achever le montage de notre dispositif expérimentalThis manuscript presents the construction of a new quantum ultracold atom experiment using strontium 84. The aim of this experiment is to study the relaxation dynamics of quantum gases initially prepared in an out-of-equilibrium state. We will investigate bidimensional gases on a lattice. This manuscript aims to describe the optical systems designed for trapping and manipulating the atoms during the experiment. Specifically, we present our optical solution to transport the atoms between locations in the vacuum chamber. We also discuss the choices we made to create the bidimensional lattice. Lastly, a quantum gas microscope is implemented to measure the spatial correlation functions from the atoms’ distribution in the lattice. A characterization of the microscope is laid out in this manuscript. Though we determined a first version of our optical systems, there are still a few steps needed to complete the experimental setup
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Comparin, Tommaso. "From few-body atomic physics to many-body statistical physics : the unitary Bose gas and the three-body hard-core model." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE042/document.
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Les gaz d'atomes ultrafroids offrent des possibilités sans précédent pour la réalisation et la manipulation des systèmes quantiques. Le contrôle exercé sur les interactions entre particules permet d'atteindre le régime de fortes interactions, pour des espèces d'atomes à la fois fermioniques et bosoniques. Dans la limite unitaire, où la force d'interaction est à son maximum, des propriétés universelles émergent. Pour les atomes bosoniques, celles-ci comprennent l'effet Efimov, l'existance surprenante d'une séquence infinie d'états liés à trois corps. Dans cette thèse, nous avons étudiés un système de bosons unitaires. Partant des cas à deux et à trois corps, nous avons montrés que le modèle choisi capturait correctement les caractéristiques universelles de l'effet Efimov. Pour le modèle à N-corps, nous avons développé un algorithme de Monte Carlo quantique capable de réaliser les différentes phases thermodynamiques du système : gaz normal à haute-température, condensat de Bose-Einstein, et liquide d'Efimov. Un unique composant de notre modèle resterait pertinent à la limite de température infinie, à savoir la répulsion corps dur à trois corps, qui constitue une généralisation du potentiel classique entre sphères dures. Pour ce modèle, nous avons proposé une solution au problème d'empilement compact en deux et trois dimensions, fondée sur une Ansatz analytique et sur la technique de recuit simulé. En étendant ces résultats à une situation de pression finie, nous avons montré que le système présente une transition de fusion discontinue, que nous avons identifié à travers la méthode de Monte CarloUltracold atomic gases offer unprecedented possibilities to realize and manipulate quantum systems. The control on interparticle interactions allows to reach the strongly-interacting regime, with both fermionic and bosonic atomic species. In the unitary limit, where the interaction strength is at its maximum, universal properties emerge. For bosonic atoms, these include the Efimov effect, the surprising existence of an infinite sequence of three-body bound states. In this thesis, we have studied a system of unitary bosons. Starting from the two- and three-body cases, we have shown that the chosen model correctly captures the universal features of the Efimov effect. For the corresponding many-body problem, we have developed a quantum Monte Carlo algorithm capable of realizing the different thermodynamic phases in which the system may exist: The high-temperature normal gas, Bose-Einstein condensate, and Efimov liquid. A single ingredient of our model would remain relevant in the infinite-temperature limit, namely the three-body hard-core repulsion, which constitutes a generalization of the classical hard-sphere potential. For this model, we have proposed a solution to the two- and three-dimensional packing problem, based on an analytical ansatz and on the simulated-annealing technique. Extending these results to finite pressure showed that the system has a discontinuous melting transition, which we identified through the Monte Carlo method
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Bosch, Aguilera Manel. "Coherence and relaxation of an optically-driven bosonic quantum gas : experiments with ultracold ytterbium atoms." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS174.
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Dans ce travail de thèse, je présente une série d'études expérimentales réalisées avec des gaz d'ytterbium ultrafroids excités sur différentes transitions optiques. L'ytterbium appartient à la famille des atomes dits alcalino-terreux. Ces atomes possèdent une structure électronique riche, avec une transition d’horloge exempte d’émission spontanée et une transition étroite d'intercombinaison. Avec des expériences de spectroscopie sur la transition d'horloge dans des réseaux optiques profonds, je montre notre capacité à exciter cette transition de manière cohérente pendant de longues périodes. Ce contrôle est ensuite utilisé dans un premier temps en tant qu'outil pour mesurer les longueurs de diffusion des états impliqués dans la transition d'horloge et ensuite, pour préparer un petit système quantique ouvert, où la dissipation prend la forme de pertes à deux corps. En branchant ce couplage adiabatiquement, on observe une forte suppression de ces pertes, ce qui est interprété comme une signature de l'effet Zénon quantique. J'utilise finalement ce transfert cohérent pour étudier la dynamique de relaxation d'un condensat de Bose-Einstein. Enfin, je développe une étude sur un système ouvert avec des interactions fortes. Ici, on induit artificiellement de la dissipation sous la forme d'émission spontanée en utilisant la transition d'intercombinaison, et j'étudie comment la cohérence spatiale d'un superfluide dans un réseau optique est détruite. Ces expériences révèlent que la présence d'interactions fortes protège partiellement une cohérence résiduelle et entraîne un développement non-triviale de la décohérence, révélant ainsi l'émergence d'un canal de relaxation subdiffusifIn this thesis I report on a series of experimental studies performed with ultracold ytterbium gases driven in different optical transitions. Ytterbium belongs to the family of the so-called alkaline-earth-like atoms, which feature a rich electronic structure, with an optical clock transition free of spontaneous emission, and a narrow intercombination transition, making them very appealing for metrological and quantum simulation proposals. By performing spectroscopy on the clock transition, I prove on a first set of experiments in deep optical lattices our ability to drive this transition coherently for long times. This coherent control is then used for different studies. First, as tool to measure the scattering lengths of the states involved in the clock transition. Then, to prepare a small open quantum system, where dissipation arises in the form of two-body losses. By enabling the coupling adiabatically, we observe a strong suppression of these losses, which is interpreted as a signature of the quantum Zeno effect. I ultimately use the coherent driving to study the relaxation dynamics of a dissipative bulk Bose-Einstein condensate. Finally, I elaborate an investigation on a strongly-interacting open system. Dissipation is artificially induced in the form of spontaneous emission using the intercombination transition. Here, I study in which manner spontaneous emission destroys the spatial coherence of a superfluid in an optical lattice. These experiments reveal that the presence of strong interactions partially protects a residual amount of coherence and makes decoherence develop in a non-trivial manner, unveiling the emergence of a subdiffusive relaxation channel
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De, rossi Camilla. "Gaz de Bose en dimension deux : modes collectifs, superfluidité et piège annulaire." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCD060/document.
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Les gaz atomiques dégénérés représentent des systèmes modèles pour étudier la superfluidité. Ils offrent la possibilité d'explorer la physique en dimensions restreintes, profondémentdifférente par rapport au cas tridimensionnel. Nous disposons d'un gaz de Bose bidimensionnel dégénéré confiné dans un potentiel très anisotrope et dont on peut changer la géométrie dynamiquement. Une déformation contrôlée du piège permet d'exciter les modes collectifs du gaz. Nous avons fait d'abord une analyse en composantes principales du gaz, et nous avons montré que ces dernières coïncident avec les modes de Bogoliubov. Nous avons ensuite effectué une étude détaillée du mode ciseaux, dont nous nous servons pour sonder le caractère superfluide du gaz, en développant une nouvelle technique d'analyse, appelée "analyse de la moyenne locale". Enfin nous avons réalisé un piège en anneau, obtenu à l'intersection d'un piège en forme de bulle et du potentiel optique d'un faisceau qui présente un noeud d'intensité au centre, la "double nappe", et nous proposons différentes protocoles de mise en rotation des atomes dans l'anneauDegenerate atomic gases can be a versatile tool to study superfluidity. They also offer the possibility to explore the low-dimensions physics, which is deeply different from the three dimensional case. We prepare a degenerate Bose gas in a very anisotropic trap, dynamically adjustable. A controlled deformation of the trapping potential can excite the collective modes of the trapped cloud. First we perform a « principal components analysis » of the gas and we show that the principal components coincide with the Bogoliubov modes. We then restrain our analysis on the scissors mode, which we use to probe superfluidity of the sample, by introducing a new analysis technique, called « local average analysis ». Finally I will report on the realization of a ring trap, obtained by superposing a double sheet light beam to a bubble trap, and describe the different possibilities we planned to set atoms into rotation
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Holz, Sheila Magali [UNESP]. "Estabilidade de sistemas condensados com interação atrativa ou repulsiva." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/91842.
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Investigamos as soluções estacionárias e dinâmicas da equação de Gross-Pitaevskii generalizada para sistemas atômicos com um potencial confinante e termos não conservativos associados à dissipação e à alimentação atômica, visando a descrição de condensados de Bose-Einstein. Consideramos os casos de comprimentos de espalhamento negativos (interações atrativas) e positivos (interações repulsivas) entre dois átomos. Verificamos como a variação dos parâmetros associados aos termos não conservativos pode produzir situações de instabilidade resultando no fenômeno conhecido como caos espaço temporal. Por outro lado, verificamos também quais combinações de parâmetros leva a soluções de equilíbrio, tipo solitônica. Nessa pesquisa, utilizando esse modelo de campo médio com uma parametrização conhecida, estudamos as propriedades de tais sistemas para alguns valores dos parâmetros não-conservativos, por meio de métodos numéricos e variacionais.
We investigate the stationary and dynamical solutions of the Gross-Pitaevskii equation extended for atomic systems with confining potential in the presence of nonconservative terms associated to atomic dissipation and feeding, in order to describe Bose-Einstein Condensates. We considered the cases of negative (attractive interaction) and positive (repulsive interaction) two-body lenght. We verified how the variation of the parameters associated to those nonconservative terms could produce instabilities resulting in occurrence of spacetemporal chaos. In other hand, we looked for parameters combinations that give us stable solitonic-like solutions. In this research, by using the mean-field approach with a particular parameterization, we studied the properties of these systems for some values of the nonconservative parameters, by means of numerical and variational methods.
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Arnal, Maxime. "Gaz quantique dans un potentiel périodique dépendant du temps : de la modulation perturbative aux résonances de l'effet tunnel assisté par le chaos." Electronic Thesis or Diss., Toulouse 3, 2020. http://www.theses.fr/2020TOU30078.
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Les gaz quantiques ont démontré leur capacité à imiter les propriétés d'autres systèmes et constituent, à ce titre, une plateforme privilégiée pour la simulation quantique. Ces gaz, caractérisés par un haut degré de contrôle grâce à la modulation temporelle de leurs paramètres, ont surtout été étudiés dans le régime perturbatif ou dans un régime purement chaotique. Cette thèse vise à accroître les possibilités offertes par ces dispositifs en tirant partie d'une dynamique mixte, que nous appliquons au cas du transport d'ondes de matière. Nous décrivons dans ce manuscrit plusieurs études expérimentales portant sur la dynamique d'un condensat de Bose-Einstein dans un réseau optique unidimensionnel modulé en phase et en amplitude. Les expériences présentées se classent en deux catégories : (i) le régime perturbatif, pour lequel les modulations appliquées induisent peu de chaos, et (ii) le régime mixte, où coexistent à la limite classique des trajectoires régulières et chaotiques. Dans le régime perturbatif, qui constitue le premier axe de cette thèse, nous distinguons deux domaines de modulation du réseau optique. Lorsque les fréquences de modulation sont résonantes avec la structure de bandes, nous provoquons des transitions interbandes soumises à des règles de sélection. Nous démontrons alors une nouvelle méthode de refroidissement, assimilable à une évaporation dans l'espace réciproque, utilisant ces règles de sélection. Pour une modulation de phase hors résonance, la dynamique du condensat peut être décrite par un Hamiltonien effectif. Nous étudions deux de ces Hamiltoniens, qui rendent compte pour l'un d'une transition de phase quantique et pour l'autre de la renormalisation de la profondeur du réseau. Dans chaque cas nous explorons les limites de ces modèles. Le régime mixte constitue le deuxième axe d'étude de cette thèse. L'analogue classique à notre système est le pendule modulé, bien connu pour présenter des trajectoires régulières et chaotiques. Ce comportement se manifeste au niveau quantique par la présence, en plus de la structure du réseau, d'une mer chaotique. Dans ce réseau optique habillé par le chaos, nous étudions un type de transport appelé effet tunnel assisté par le chaos, qui présente des résonances susceptibles d'amplifier ou d'inhiber l'effet tunnel entre deux positions stables au sein d'un puits du réseau. Comparé aux expériences antérieures sur ce sujet, nous nous plaçons dans une configuration différente dans laquelle nous parvenons à résoudre pour la première fois ces résonances. Pour les simulateurs quantiques, ce travail ouvre la voie à un nouveau type de contrôle, avec notamment du transport à longue portéeDegenerate quantum gases have demonstrated their ability to mimic the properties of other systems and are, as such, an ideal platform for quantum simulation. These gases, characterized by a high level of control thanks to the temporal driving of their parameters, have mainly been studied either in the perturbative regime or in a purely chaotic one. The aim of the present work is to further extend the possibilities offered by such systems by taking advantage of a mixed dynamics, which we apply to the case of matter-wave transport. In this thesis, we describe several experimental studies on the dynamics of a Bose-Einstein condensate in a one-dimensional time-dependent optical lattice. The experiments that are presented fall into two categories: (i) the perturbative regime, where the applied modulations induce little chaos, and (ii) the mixed regime, where regular and chaotic trajectories coexist at the classical limit. In the perturbative regime, which was first studied during this thesis, we distinguish two modulation domains of the optical lattice. When the modulation frequencies are resonant with the band structure, we induce interband transitions that are subject to selection rules. We then demonstrate a new cooling technique, similar to evaporation but in reciprocal space, taking advantage of these selection rules. For a phase modulation out of resonance, the dynamics of the condensate can be described by an effective Hamiltonian. We study two such Hamiltonians, one of which accounts for a quantum phase transition and the other for the renormalization of the lattice depth. In each case we explore the limits of these models. The mixed regime constitutes the second focus of this thesis. The classical analogue of our system is the modulated pendulum, well-known to present both regular and chaotic trajectories. This behavior is revealed at the quantum level by the presence, in addition to the lattice structure, of a chaotic sea. In this optical lattice dressed by chaos, we study a type of transport called chaos-assisted tunneling, which presents resonances that can amplify or inhibit tunneling between two stable positions within a lattice well. Compared to previous experiments on this subject, we use a different configuration in which we manage to resolve these resonances for the first time. For quantum simulators, this work paves the way to a new type of control, including long-range transport
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Sensarma, Rajdeep. "A theoretical study of strongly interacting superfluids and superconductors." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1186581954.
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Benson, Eric. "Bose-Einstein condensation of excitons." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0017/NQ48088.pdf.
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Arlt, Jan. "Experiments on Bose-Einstein condensation." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326008.
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Davis, Matthew John. "Dynamics of Bose-Einstein condensation." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393350.
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Lewoczko-Adamczyk, Wojciech. "Bose-Einstein condensation in microgravity." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2009. http://dx.doi.org/10.18452/15970.
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Ultra-kalte atomare Gase werden in zahlreichen Laboren weltweit untersucht und finden unter anderem Anwendung in Atomuhren und in Atominterferometer. Die Einsatzgebiete erstrecken sich von der Geodäsie über die Metrologie bis hin zu wichtigen Fragestellungen der Fundamentalphysik, wie z.B. Tests des Äquivalenzprinzips. Doch die beispiellose Messgenauigkeit ist durch die irdische Gravitation eingeschränkt. Zum einen verzerrt die Schwerkraft das Fallenpotential und macht damit die Reduktion der atomaren Energie unter einem bestimmten Limit unmöglich. Zum anderen werden die aus einer Falle frei gelassenen Teilchen durch die Erdanziehung beschleunigt und so ist deren Beobachtungszeit begrenzt. Im Rahmen dieser Arbeit werden die Ergebnisse des Projektes QUANTUS (Quantengase Unter Schwerelosigkeit) dargestellt. Auf dem Weg zur Implementierung eines Quantengasexperimentes im Weltraum wurde innerhalb einer deutschlandweiten Zusammenarbeit eine kompakte, portable und mechanisch stabile Apparatur zur Erzeugung und Untersuchung eines Bose-Einstein-Kondensats (BEC) unter Schwerelosigkeit im Fallturm Bremen entwickelt. Sowohl die Abbremsbeschleunigung von bis zu 50 g als auch das begrenzte Volumen der Fallkapsel stellen hohe Ansprüche an die mechanische Stabilität und die Miniaturisierung von optischen und elektronischen Komponenten. Der Aufbau besteht aus einer im ultra-hoch Vakuum geschlossenen magnetischen Mikrofalle (Atomchip) und einem kompakten auf DFB-Dioden basierenden Lasersystem. Mit diesem Aufbau ließ sich das erste BEC unter Schwerelosigkeit realisieren und nach 1 Sekunde freier Expansion zu beobachten. Weder die schwache Krümmung des Fallenpotentials noch die lange Beobachtungszeit würden in einem erdgebundenen Experiment realisierbar. Die erfolgreiche Umsetzung des Projektes eröffnet ein innovatives Forschungsgebiet - degenerierte Quantengase bei ultratiefen Temperaturen im pK-Bereich, mit großen freien Evolutions- und Beobachtungszeiten von mehreren Sekunden.Recently, cooling, trapping and manipulation of neutral atoms and ions has become an especially active field of quantum physics. The main motivation for the cooling is to reduce motional effects in high precision measurements including spectroscopy, atomic clocks and matter interferometry. The spectrum of applications of these quantum devices cover a broad area from geodesy, through metrology up to addressing the fundamental questions in physics, as for instance testing the Einstein’s equivalence principle. However, the unprecedented precision of the quantum sensors is limited in terrestial laboratories. Freezing atomic motion can be nowadays put to the limit at which gravity becomes a major perturbation in a system. Gravity can significantly affect and disturb the trapping potential. This limits the use of ultra-shallow traps for low energetic particles. Moreover, free particles are accelerated by gravitational force, which substantially limits the observation time. Targeting the long-term goal of studying cold quantum gases on a space platform, we currently focus on the implementation of a Bose-Einstein condensate (BEC) experiment under microgravity conditions at the drop tower in Bremen. Special challenges in the construction of the experimental setup are posed by a low volume of the drop capsule as well as critical decelerations up to 50g during recapture at the bottom of the tower. All mechanical and electronic components were thus been designed with stringent demands on miniaturization and mechanical stability. This work reports on the observation of a BEC released from an ultra-shallow magnetic potential and freely expanding for one second. Both, the low trapping frequency and long expansion time are not achievable in any earthbound laboratory. This unprecedented time of free evolution leads to new possibilities for the study of BEC-coherence. It can also be applied to enhance the sensitivity of inertial quantum sensors based on ultra-cold matter waves.
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Marelic, Jakov. "Bose-Einstein condensation of photons." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/59351.
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A Bose-Einstein condensate can be made of photons. The photons are held at thermodynamic equilibrium in a dye-filled microcavity and pumped with a laser. Thermalisation can be demonstrated and above the threshold a Bose-Einstein condensate will form. A Mach-Zehnder interferometer is built and used to measure the spatial and temporal first-order coherence under various conditions. We build a momentum-resolved spectrometer and use it to obtain views into the phase-space distribution of the photon condensate. We put an upper bound on the value of the interaction strength parameter and find that the microcavity system is ergodic even when not at thermal equilibrium. We build a setup to stabilise the pump laser power with the aim to observe the λ-point of the condensate.
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Zamfirescu, Marian. "Couplage excitons-lumière dans des hétérostructures à base de semi-conducteurs à grand gap." Clermont-Ferrand 2, 2003. http://www.theses.fr/2003CLF21418.
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Ce travail est consacré à l'étude théorique et expérimentale du couplage lumière-matière dans des structures à base de semi-conducteurs à grand gap GaN et ZnO et dans les nitrures InGaAsN à petit gap. La partie expérimentale de la thèse est dédiée à l'analyse par photoluminescence résolue en temps des processus de recombinaison radiative et non-radiative dans des puits quantiques InGaAsN à faible teneur en azote. Les résultats obtenus montrent que la dynamique de recombinaison est dominée par les processus non-radiatifs dus à la matrice hôte ( InGaAs) de la structure plutôt qu'à l'insertion d'azote. Nous présentons ensuite une étude des propriétés optiques des matériaux semi-conducteurs à grand gap. La réflectivité des puits quantiques GaN/A1GaN présente des résonances excitoniques larges dont il est difficile d'extraire des paramètres excitoniques précis. Nous avons développé une technique d'analyse des spectres de réflectivité expérimentaux basée sur la comparaison de la transformée de Fourier de ces spectres à la réflexion résolue en temps calculée d'après un modèle réaliste. Ainsi, nous séparons et déterminons les contributions homogène et inhomogène de l'élargissement des raies excitoniques. Cette méthode d'analyse est appliquée sur des spectres de réflectivité de puits quantiques GaN/A1GaN et ZnO massif. Nous avons montré que le couplage exciton-lumière est grand dans ces structures. Dans les puits quantiques GaN/A1GaN, la force d'oscillateur des excitons dépend fortement de l'épaisseur du puits à cause du champ de polarisation. A partir des paramètres obtenus, nous proposons des modèles de microactivités à base de GaN et ZnO, pouvant fonctionner en régime de couplage fort à température ambiante. Nous montrons qu'à l'équilibre thermodynamique, la température critique de condensation de Bose des polaritons dans ces structures est de l'ordre de 500K, ce qui rend possible la réalisation d'un nouveau type de composant, le laser à polaritons
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Ritter, Stephan. "Probing coherence during Bose-Einstein condensation /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17215.
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Mewes, Marc-Oliver. "Bose-Einstein condensation of sodium atoms." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10768.
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Fried, Dale G. (Dale George) 1968. "Bose-Einstein condensation of atomic hydrogen." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84757.
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Mallardeau, Catherine. "L'hydrogène atomique polarisé : interaction avec les films d'Helium : expérience de compression." Paris 6, 1986. http://www.theses.fr/1986PA066186.
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Etude expérimentale de certains mécanismes de recombinaison de H| afin de comprendre les limites à l'obtention de la condensation de Bose Einstein. Mesure de l'énergie d'adsorption de H sur une couche mince 4He en fonction de l'épaisseur de la couche, paramètre qui donne les limites de stabilisation de H à basse température; obtention de la stabilisation sur des couches biomoléculaires. Construction d'un dispositif expérimental pour comprimer le gaz H| en champ magnétique de 20t, pour étudier le taux de recombinaison à 3 corps de H à haute densité et en champ magnétique intense.
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Carr, Lincoln D. "Solitons in Bose-Einstein condensates /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9702.
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Dunningham, Jacob Andrew. "Quantum phase of Bose-Einstein condensates." Thesis, University of Oxford, 2001. http://ora.ox.ac.uk/objects/uuid:b6cc8b74-753c-4b3e-ad5e-68bd7e32b652.
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The quantum phase of a Bose-Einstein condensate has long been a subject fraught with misunderstanding and confusion. In this thesis we provide a consis- tent description of this phenomenon and, in particular, discuss how phase may be defined, created, manipulated, and controlled. We begin by describing how it is possible to set up a reference condensate against which the phase of other condensates can be compared. This allows us to think of relative phases as if they were absolute and gives a clear and precise definition to 'the phase of a condensate'. A relative phase may also be established by coupling condensates and we show how this can be controlled. We then extend this model to explain how the phase along a chain of coupled condensates can lock naturally without the need for any measurements. The second part of the thesis deals primarily with the link between entangle- ment and phase. We show that, in general, the more entangled a state is, the better its phase resolution. This leads us to consider schemes by which maximally entangled states may be able to be created since these should give the best prac- tical advantages over their classical counterparts. We consider two such states: a number correlated pair of condensates and a Schrodinger cat state. Both schemes are shown to be remarkably robust to loss. A comparison of the merits of these two states, as the inputs to an interferom- eter, reveals very different behaviours. In particular, the number correlated state performs significantly better than the cat state in the presence of loss, which means that it might be useful in interferometry and frequency standard schemes where phase resolution is of the utmost importance. Finally, we propose a scheme for concentrating the entanglement between con- densates, which is an important step in quantum communication protocols. This, along with the ability to manipulate phase and entanglement, suggests that the future for condensates holds not only academic interest but great potential for practical applications.
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Moulder, Stuart. "Persistent currents in Bose-Einstein condensates." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648095.
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Pereira, Dos Santos Franck. "Condensation de Bose-Einstein de l'hélium métastable." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2002. http://tel.archives-ouvertes.fr/tel-00002267.
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Nous présentons dans cemémoire la réalisation expérimentale de la condensation de
Bose-Einstein de l'hélium métastable $2^3S_1$ polarisé. Nous
commençons par y résumer les prédictions théoriques concernant les
taux de collisions élastiques et inélastiques entre atomes
métastables polarisés. Ce sont sur ces prédictions très
encourageantes que reposait l'espoir d'atteindre la condensation
de Bose-Einstein de l'hélium métastable. Nous présentons ensuite
le dispositif expérimental que nous avons construit. La technique
que nous avons utilisée consiste à pré-refroidir un échantillon de
gaz dans un piège magnéto-optique, que l'on charge à partir d'un
jet atomique intense et ralenti. La densité dans le piège
magnéto-optique est limitée par de très forts taux de collisions
inélastiques assistées par la lumière, que nous avons mesurés pour
une large gamme de paramètres de piégeage. Le gaz piégé est
ensuite transféré dans un piège magnétostatique où il est refroidi
par la technique du refroidissement évaporatif jusqu'au seuil de
dégénérescence quantique. Nous avons mesuré des temps de vie des
atomes dans le piège magnétique de l'ordre de la minute, ce qui
démontre que les collisions inélastiques sont supprimées par au
moins deux ordres de grandeur dès lors que les atomes sont
polarisés. A l'aide d'une méthode de détection purement optique,
basée sur l'absorption d'un faisceau laser résonnant à la
traversée du nuage atomique, nous avons pu mettre en évidence la
condensation de Bose-Einstein. Finalement, des mesures du nombre
d'atomes et de la taille du condensat, nous avons déduit une
estimation de la longueur de diffusion, $a=(16\pm8)$ nm.
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Shvarchuck, Igor Yevgeniiovich. "Bose-Einstein condensation into non-equilibrium states." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2003. http://dare.uva.nl/document/67440.
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Bedingham, Daniel John. "Quantum field theory and Bose Einstein condensation." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249588.
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Sinclair, Christopher David James. "Bose-Einstein condensation in microtraps on videotape." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428140.
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Jones, M. P. A. "Bose Einstein condensation on an atom chip." Thesis, University of Sussex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270728.
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Grimm, Douglas. "The dynamics of collapsing Bose-Einstein condensates." View electronic text, 2002. http://eprints.anu.edu.au/documents/disk0/00/00/07/64/index.html.
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Thesis (BSc. (Hons))--Australian National University, 2002.Available via the Australian National University Library Electronic Pre and Post Print Repository. Title from title screen (viewed Mar. 28, 2003). "A thesis submitted for the degree of Bachelor of Science with Honours of The Australian National University" Bibliography: p. 45.
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Pulido, Daniel. "Instability in a cold atom interferometer." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0430103-095432.
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Palzer, Stefan. "Single impurities in a Bose-Einstein condensate." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609015.
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Petrov, Dmitry Sergeevich. "Bose-Einstein condensation in low-dimensional trapped gases." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2003. http://dare.uva.nl/document/67425.
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Fletcher, Richard Jonathan. "Bose-Einstein condensation and superfluidity in two dimensions." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709200.
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Harrison, Brent. "Bose-Einstein condensation from a gluon transport equation." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29494.
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In this thesis we investigate the evolution of the quark gluon plasma, as produced in the early stages of a relativistic heavy ion collision, towards equilibrium. To this end we put forward a new numerical scheme to solve the QCD Boltzmann equation in the small-scattering angle approximation, which we develop here for the quenched limit of QCD. We initially restrict our analysis to spatially homogeneous systems of gluons distributed isotropically in momentum space. With our scheme we confirm results of Blaizot et al. [1], in particular that for certain “overpopulated” initial conditions, a transient Bose-Einstein condensate emerges during equilibriation in a finite time. We further analyse the dynamics of the formation of this condensate. We then extend our scheme to systems with cylindrically symmetric momentum distributions, in order to investigate the effects of anisotropy. In particular we compare the rates at which isotropization and equilibriation occur. We also compare our results from the small-scattering angle scheme to the relaxation-time approximation.
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Stickney, James Arthur. "A theoretical analysis of Bose-Einstein condensate based beamsplitters, interferometers, and transistors." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-032708-124639/.
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