Dissertations / Theses on the topic 'Cold atomics physics'
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Peyronel, Thibault (Thibault Michel Max). "Quantum nonlinear optics using cold atomic ensembles." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84393.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 219-232).
The fundamental properties of light derive from its constituent particles, photons, which are massless and do no interact with each other. The realization of interactions between photons could enable a wide variety of scientific and engineering applications. In particular, coherent interactions would open the path for the simulation of quantum systems with light. Photon-photon interactions can be mediated by matter, in our case cold atomic ensembles, which provide a nonlinear medium. In conventional nonlinear media, the nonlinearities are negligibly weak at intensities corresponding to single photons and nonlinear optics at the few-photon level is a long-standing goal of optical and quantum science. In this thesis, we report on two different experimental approaches to create optical media with giant nonlinearities. Both approaches rely on Electromagnetically Induced Transparency, in which photons traveling in the medium are best described as part-matter part-light quantum particles, called polaritons. In our first approach, we achieve low-light nonlinearities by loading ensembles of cold atoms in a hollow-core photonic crystal fiber to enhance the polariton-photon interactions. In our second approach, the photons are coupled to strongly interacting Rydberg atoms, which mediate large interactions between single quanta of light. Moreover, the intrinsic nature of these interactions can be tailored to take on a coherent dispersive form.
by Thibault Peyronel.
Ph.D.
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Miller, Daniel E. (Daniel Edward). "Studying coherence in ultra-cold atomic gases." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/45398.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Physics, September 2007.Includes bibliographical references (leaves 130-141).
This thesis will discuss the study of coherence properties of ultra-cold atomic gases. The atomic systems investigated include a thermal cloud of atoms, a Bose-Einstein condensate and a fermion pair condensate. In each case, a different type of measurement is performed. However, all of the experiments share a common tool: an optical lattice which is used to probe these atomic gases. In the first case, we use an auto-correlation technique to study the interference pattern produced by a gas of atoms, slightly above the Bose -Einstein condensate transition temperature. A moving optical lattice is used to split and recombine the single particle atomic wavefunction. Analogous to a Young's double slit experiment, we observe high contrast interference which is well described by the model which we develop. When we address only a velocity subset of the thermal sample, however, the contrast is enhanced and deviates from this model. In a second experiment we measure the coherence of a diatomic molecular gas, as well as the atomic Bose-Einstein condensate from which it was created. We use Bragg spectroscopy, in which atoms exchange photons with a moving optical lattice, transferring momentum to the atoms. This process can reveal the velocity distribution of the sample as energy and momentum are conserved only for a specific velocity class. Based on this measurement, we find that the atomic coherence is transferred directly to the molecular gas. We also discuss similar preliminary measurements performed on a fermion pair condensate in the BEC-BCS crossover. In a third experiment we study a fermion pair condensate into a 3D optical lattice. Such a system shares many similarities with electrons in solid materials which exhibit superconductivity, and can offer insight into mechanism which result in this behavior. We infer coherence from the sharp interference pattern observed in the expanding gas, after release. Finally, we study the abrupt onset of dissipation observed in a fermion pair condensate, as a function of velocity, in a moving optical lattice.
(cont.) We equate this threshold with the Landau critical velocity, and take measurements throughout the BEC-BCS crossover. The critical velocity is found to be maximum near unitarity, where the loss mechanism is predicted to crossover from phonon-like excitations to pair breaking.
by Daniel E. Miller.
Sc.D.
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Drayna, Garrett Korda. "Novel Applications of Buffer-Gas Cooling to Cold Atoms, Diatomic Molecules, and Large Molecules." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:26718757.
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Cold gases of atoms and molecules provide a system for the exploration of a diverse set of physical phenomena. For example, cold gasses of magnetically and electrically polar atoms and molecules are ideal systems for quantum simulation and quantum computation experiments, and cold gasses of large polar molecules allow for novel spectroscopic techniques. Buffer-gas cooling is a robust and widely applicable method for cooling atoms and molecules to temperatures of approximately 1 Kelvin. In this thesis, I present novel applications of buffer-gas cooling to obtaining gases of trapped, ultracold atoms and diatomic molecules, as well as the study of the cooling of large organic molecules. In the first experiment of this thesis, a buffer-gas beam source of atoms is used to directly load a magneto-optical trap. Due to the versatility of the buffer-gas beam source, we obtain trapped, sub-milliKelvin gases of four different lanthanide species using the same experimental apparatus. In the second experiment of this thesis, a buffer-gas beam is used as the initial stage of an experiment to directly laser cool and magneto-optically trap the diatomic molecule CaF. In the third experiment of this thesis, buffer-gas cooling is used to study the cooling of the conformational state of large organic molecules. We directly observe conformational relaxation of gas-phase 1,2-propanediol due to cold collisions with helium gas. Lastly, I present preliminary results on a variety of novel applications of buffer-gas cooling, such as mixture analysis, separation of chiral mixtures, the measurement of parity-violation in chiral molecules, and the cooling and spectroscopy of highly unstable reaction intermediates.Chemical Physics
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Schwonek, James Phillip. "A study of a cold atomic hydrogen beam source." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/37496.
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Keilmann, Tassilo. "Strongly correlated quantum physics with cold atoms." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-107331.
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Huillery, Paul. "Few and Many-body Physics in cold Rydberg gases." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112040/document.
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Au cours de cette thèse, la physique des systèmes en interaction à été étudié expérimentalement à partir de gaz froids d'atomes de Rydberg. Les atomes de Rydberg sont des atomes dans un état fortement excités et ils ont la propriété d'interagir fortement du fait d'interactions électrostatiques à longue portée. Le premier résultat majeur de cette thèse est l'observation expérimentale d'un processus à quatre corps. Ce processus consiste en l'échange d'énergie interne entre quatre atomes de Rydberg induit par leurs interactions mutuelles. Il a été possible, en plus de son observation expérimentale, de décrire théoriquement ce processus, au niveau quantique. L'excitation par laser des gaz d'atomes de Rydberg en forte interaction a aussi été étudiée durant cette thèse. Cette situation donne lieu à de très intéressants comportements à N-corps. Ce sujet d'intérêt fondamental pourrait aussi amener à d'éventuelles applications pour la réalisation de simulateurs quantiques ou de sources de lumière non classiques. Un second résultat majeur de cette thèse est l'observation expérimentale d'une statistique fortement sub-poissonienne, i.e corrélée de l'excitation Rydberg. Ce résultat confirme le caractère à N-corps de tels systèmes. Le troisième résultat majeur de cette thèse est le développement d'un modèle théorique pour l'excitation par laser des gaz d'atomes de Rydberg en forte interaction. En utilisant les états quantiques dit états collectifs de Dicke, il a été possible de mettre au jour de nouveaux mécanismes liés au comportement à N-corps de ces sytèmes atomiques en forte interactionUring this thesis, the Physics of interacting systems has been investigated experimentally using Cold Rydberg gases. Rydberg atoms are highly excited atoms and have the property to interact together through long-range electrostatic interactions.The first highlight of this thesis is the direct experimental observation of a 4-body process. This process consists in the exchange of internal energy between 4 Rydbergs atoms due to their mutual interactions. In addition to its observation, it has been possible to describ this process theoretically at a quantum level.The laser excitation of strongly interacting Rydberg gases has been also investigated during this thesis. In this regime, the interactions between Rydberg atoms give rise to very interesting many-body behaviors. In addition to fundamental interest, such systems could be used to realyze quantum simulators or non-classical light sources.A second highlight of this thesis is the experimental observation of a highly sub-poissonian, i.e correlated, excitation statistics. This result confirms the many-body character of the investigated system.The third highlight of this thesis is the development of a theoretical model to describ the laser excitation of strongly interacting Rydberg gases. Using the so-called Dicke collective states it has been possible to point out new mechanismes related to the many-body character of strongly atomic interacting systems
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Côté, Joseph Noël Robin. "Ultra-cold collisions of identcial atoms." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32632.
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Sanguinetti, Stefano. "ATOMIC PARITY VIOLATION IN HEAVY ALKALIS: Detection by Stimulated Emission for Cesium and Traps for Cold Francium." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2004. http://tel.archives-ouvertes.fr/tel-00006785.
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Le travail présenté porte sur les progrès récents d'expériences de spectroscopie atomique sur césium et francium, visant à des mesures précises de violation de parité (PV) dans ces atomes. Dans le cadre d'une “thèse en cotutelle”, le candidat s'est consacré d'une part aux mesures PV préliminaires (8% de précision) de l'actuelle expérience Cs au LKB à Paris, et d'autre part à la préparation d'un échantillon d'atomes radioactifs de Fr (production et piégeage) aux LNL (INFN) en Italie. Ces deux expériences sont à des stades très différents. Les mesures présentées pour le Cs s'inscrivent en fait dans la lignée d'un travail commencé en 1991, pour la détection de PV par émission stimulée. L'expérience italienne est par contre à ses débuts: pour pouvoir sonder les propriétés du Fr, instable, il faut d'abord produire et rassembler un nombre suffisant d'atomes. La conception de montages PV qui ont démontré leur validité sur le césium constitue une solide base de départ pour le cas du francium.
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Mudarikwa, Lawrence. "Cold atoms in a ring cavity." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5843/.
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An ensemble of atoms coupled to a high finesse optical cavity is an ideal test bed for the study of the cooperative behaviour of atom-photon systems. Dicke showed that an ensemble of excited atoms coupled to a light field interacts with the light in a collective and coherent fashion leading to the emission of highly directional spontaneous emission whose intensity scales with the square of the number of atoms, a phenomenon known as superradiance. This thesis describes the build of an experiment to study cooperative atom-photon interactions in a ring cavity. Particular focus is given to the cavities used in the experiment. Firstly a transfer cavity used for transferring stability to off-resonant lasers in the experiment, this was developed with the capability of exploiting Gouy phase degeneracies to produce tightly spaced frequency discriminants to be used as lock points. Secondly the ring cavity for the experiment which is atypical in its design allowing for bidirectional probing of the cavity mode and dynamic manipulation of the intra-cavity optical lattice. An intra-cavity MOT was produced and collective strong coupling was observed in the cavity with an Neff=6400 atoms coupled to the cavity mode.
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Trachy, Marc Lawrence. "Photoassociative ionization in cold rubidium." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/695.
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Scott, Robin George. "Cold atoms in optical lattices." Thesis, University of Nottingham, 2003. http://eprints.nottingham.ac.uk/10010/.
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This thesis describes the behaviour of cold atoms in optical lattices. In particular, it explores how transport through the energy bands of the optical lattice can be used to study quantum chaos and Bose-Einstein condensation. Firstly, this study examines the dynamics of ultra-cold sodium atoms in a one-dimensional optical lattice and a three-dimensional harmonic trap, using both semi-classical and quantum-mechanical analyses. The atoms show mixed stable-chaotic classical dynamics, which originate from the intrinsically quantum-mechanical nature of the energy band. The quantised energy levels exhibit Gutzwiller fluctuations, and the wavefunctions are scarred by an unstable periodic orbit. Distinct types of wavefunction are identified and related directly to particular parts of the classical phase space via a Wigner function analysis. Secondly, this report studies the dynamics of a rubidium Bose-Einstein condensate in a one-dimensional optical lattice and three-dimensional harmonic trap. The condensates are set in motion by displacing the trap and initially follow simple semi-classical paths, shaped by the lowest energy band. Above a critical displacement, the condensate undergoes Bragg reflection, and performs Bloch oscillations. After multiple Bragg reflections, solitons and vortices form which damp the centre-of-mass motion. Finally, the dynamics of Bose-Einstein condensates in optical lattices are investigated for different parameter regimes, as realised in recent experiments. The results reveal how the experiments can be understood, and identify regimes in which vortices trigger explosive expansion of the condensate.
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Veissier, Lucile. "Quantum memory protocols in large cold atomic ensembles." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00977307.
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Les mémoires quantiques sont un élément essentiel dans le domaine de l'information quantique, en particulier pour la mise en oeuvre de communications quantiques sur de longues distances. Une mémoire quantique a pour but de stocker un état quantique de la lumière, comme par exemple un bit quantique (qubit), et de le réémettre après un délai donné. Les ensembles atomiques sont de bons candidats pour construire de telles mémoires quantiques, car il est possible d'obtenir de fort couplage lumière-matière dans le cas d'un grand nombre d'atomes. De plus, la notion d'effet collectif, qui est renforcé pour de large profondeur optique, permet en principe une efficacité de stockage proche de l'unité. Ainsi, dans cette thèse, un piège magnéto-optique de césium à forte densité optique est utilisé pour l'implémentation d'un protocole de mémoire quantique basé sur la transparence induite électromagnétiquement (EIT). Tout d'abord, le phénomène EIT est étudié à travers un critère de discrimination entre les modèles d'EIT et de séparation Autler-Townes. Nous rapportons ensuite la mise en oeuvre d'une mémoire basée sur l'EIT pour des qubits photoniques encodés en moment angulaire orbital (OAM) de la lumière. Une mémoire réversible pour des modes de Laguerre-Gauss est réalisée, et nous démontrons que la mémoire optique préserve le sens de la structure hélicoïdale au niveau du photon unique. Ensuite, une tomographie quantique complète des états réémis est effectuée, donnant des fidélités au-dessus de la limite classique. Cela montre que notre mémoire optique fonctionne dans le régime quantique. Enfin, nous présentons la mise en oeuvre du protocole dit DLCZ dans notre ensemble d'atomes froids, permettant la génération de photons uniques annoncés. Une détection homodyne nous permet de réaliser la tomographie quantique de l'état photonique ainsi créé.
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Langmack, Christian Bishop. "Universal Loss Processes in Bosonic Atoms with Positive Scattering Lengths." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385483878.
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Steer, Edward. "Development and characterisation of a cold molecule source and ion trap for studying cold ion-molecule chemistry." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:13c3a622-ba78-4a53-902c-666ec461f708.
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A novel apparatus, combining buffer-gas cooling, electrostatic velocity selection and ion trapping, has been constructed and characterised. This apparatus is designed to investigate cold ion-molecule chemistry in the laboratory, at a variable translational and internal (rotational) temperature. This improves on previous experiments with translationally cold but rotationally hot molecule sources. The ability to vary the rotational temperature of cold molecules will allow for the experimental investigation of post-Langevin capture theories.
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Reinhed, Peter. "Ions in cold electrostatic storage devices." Doctoral thesis, Stockholm : Department of physics, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-32659.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Härtill 4 uppsatser.
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Perea-Ortiz, Marisa. "Progress towards a quantum simulator with cold atoms." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5774/.
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This thesis presents work toward a quantum simulator with cold atoms. Characteristic and defining subsystems of the experimental setup are presented. Among them there are: the self-made viewports for ultra-high vacuum using indium seals, work on a modular laser system, for laser cooling, with miniaturised optics for the optimization of double path acusto-optic modulator. Work on a computer control to implement past slot is also presented. A versatile detection system for absorption imaging was designed and built. This detection system is stable, easy to align and exchange of magnification is simple. As well, a high resolution imaging system was designed, built and tested. This imaging system uses commercial microscope objectives and has been designed to work with four different microscope objective. Magnification of 5x, 10x 20x and 50x are possible. With the maximum magnification of 50x a resolution of 1.74μm for 780nm was achieved. Also a camera control for in-situ absorption imaging was programmed. Calculation of number of atoms and temperature were implemented in the program, as well as a defringing algorithm. A new method for temperature calculation for atoms held in a magnetic quadrupole trap was developed and tested, giving similar calculation of temperature as the commonly known time of flight (TOF) method. It is shown that this new method gives better results than the common TOF method for short time of flight. Characterization of atom losses and heating in the production of a Bose-Einstein condensate were performed.
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Rammeloo, Clemens Vincent. "Optimisation of a compact cold-atoms interferometer for gravimetry." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8146/.
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The work presented in this thesis focusses on the development of a transportable atom-interferometry experiment and a compact fibre laser system towards precision measurements of gravitational acceleration. Interference fringes are shown with clouds of cold 87Rb atoms using co-propagating laser beams to drive stimulated Raman transitions. This is demonstrated both inside and outside of laboratory environments for which an integrated and transportable experiment is constructed. Further improvements are presented that enable the generation of clouds containing 1.7 · 108 atoms at a rate of 2.5 Hz and having a temperature of (7 ± 1) μK. This is largely due to the development of a compact laser system based on all-fibre coupled components. It is demonstrated that the laser system designed here can achieve fast frequency sweeps over 1.8 GHz within 2 ms, making it widely applicable in compact atom-interferometry experiments with rubidium atoms. This is shown by creating a Mach–Zehnder type interferometer with counter-propagating Raman beams, thus enabling measurements of gravitational acceleration. Since the laser system uses only two lasers and one fibre amplifier, a significant reduction in size is achieved, as well as a decrease in the total power consumption of the overall experiment by a third to (162 ± 7) W.
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Doherty, William Gerard. "Cold atom production via the photo dissociation of small molecules." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:523f87e0-3f19-4382-941c-74b06023b767.
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This thesis describes the development of a relatively novel technique for the gen- eration and subsequent trapping of cold species. Molecules in a pulsed supersonic expansion are photolysed, such that the centre-of-mass velocity vector of one of the fragments is equal in magnitude but opposed in orientation to the lab-frame velocity of the precursor molecule. This technique, known as ‘Photostop’, leaves a fraction of the fragments with a narrow velocity distribution, centered around zero velocity in the lab-frame. They can be shown to have zero velocity by changing the time between photodissociation and ionisation; fragments with a high kinetic energy will leave the ionisation volume prior to interrogation. The underlying velocity distribu- tion is uncovered by using the velocity-map imaging technique, and the temperature of the fragments can be determined. The method was originally optimised for the molecular case. Cold NO has been produced from the dissociation of NO₂ molecules, and a single rotational state has been shown to remain in the ionisation volume 10 μs after dissociation, implying a sample temperature of 1.17 K. Using the optimised experimental conditions de- rived from the velocity cancellation of NO, the atomic case is demonstrated for the dissociation of Br₂ to give zero-velocity Br fragments. The Br atoms are seen for delay times in excess of 100 μs, showing the greater applicability of the method to the atomic case. The temperature of the residual atoms is shown to be in the milliKelvin regime, as determined through detailed Monte Carlo simulation of the motion of the stopped atoms. The possibility of trapping the ultracold Br atoms in a magnetic field is explored, and a quadrupolar trap created between two per- manent bar magnets is demonstrated to confine the atoms spatially, within the ion extraction optics, for delays in excess of 1 ms. The Photostop technique is intended to be a stepping stone on the way to widening the number of chemical species available for study in the ultracold regime. The possibility of improvements to the experiment is considered, in order to increase the efficiency of the experiment such that the number density becomes high enough to be viable as a source of atoms for use in cold chemical reactive studies. The possibility of extending the method so as to be used as a tunable velocity source of atoms is also discussed.
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Zhu, Lingziao. "A cold atoms gravimeter for use in absolute gravity comparisons." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8152/.
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This thesis describes the construction of high precision absolute gravimeter, aiming at realising a comparison with a state-of-the-art gravimeter. The instrument is based on performing Raman atom interferometry on ensembles of laser-cooled 87Rb atoms in an atomic fountain. The highlight of this work is the demonstration of an IQ modulator based optical single-sideband (OSSB) laser system providing a highly coherent light source. The advantage this brings to atom interferometry is the suppression of the unwanted sidebands, eliminating interference effects, especially the spatially dependent Rabi frequency and the interferometric phase shift. Recently 5x106 atoms were launched at a rate of 0.5 Hz with a temperature of 10 �K. After improving the vibration isolation, we have observed interference fringes with a sensitivity of 225 �Gal/pHz. The preliminary accuracy is estimated to be 218 �Gal. A study of systematic noise and bias sources has been undertaken, �finding that the limitation of the above performance is the vibration noise and Coriolis effect, respectively. The apparatus has been transported to NERC Space Geodesy Facility in Herstmonceux, where a comparison campaign is in preparation.
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Zhang, Dongqing. "Aspects of cold bosonic atoms with a large scattering length." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1164823171.
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Hucul, David (David Alexander). "Magnetic super-exchange with ultra cold atoms in spin dependent optical lattices." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58068.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 65-68).
The methods of atomic physics offer a unique opportunity to study strongly correlated many body systems. It is possible to confine BECs in periodic optical lattices to form an analog of a solid state system. The study of these cold atoms in optical lattice systems may prove a very useful testing ground for novel states of matter, testing fundamental condensed matter theory, and may help illuminate a possible connection between the mechanism behind high temperature superconductivity and quantum magnetism. This thesis will focus on trapping cold bosonic atoms in spin dependent optical lattices to engineer a system that behaves according to the Hubbard model. By loading the atoms into a state dependent lattice, it may be possible to explore the full phase space of the Heisenberg model and see magnetic super exchange-driven magnetic ordering in a variety of lattice geometries. The aim of this thesis is primarily to explore some of the tools that may be needed accomplish this task.
by David Hucul.
S.M.
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Song, Jianjun. "Optically generated gauge potentials and their effects in cold atoms /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202008%20SONG.
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Au, Yat Shan. "Inelastic collisions of atomic thorium and molecular thorium monoxide with cold helium-3." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11318.
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We measure inelastic cross sections for atomic thorium (Th) and molecular thorium monoxide (ThO) in collisions with $^3$He at temperatures near 1 K. We determine the Zeeman relaxation cross section for Th ($^3$F$_2$) to be $\sim 2 \times 10^{-17}$~cm$^{-2}$ at 800~mK. We study electronic inelastic processes in Th ($^3$P$_0$) and find no quenching even after $10^6$ collisions at 800~mK. We measure the vibrational quenching cross section for ThO~(X,~$\nu=1$) to be $(7.9 \pm 2.7) \times 10^{-19}$~cm$^{-2}$ at 800~mK. Finally, we observe indirect evidence for ThO (X, $\nu=0$)--$^3$He van der Waals complex formation, and measure the 3-body recombination rate constant to be $\Gamma_3 = (8 \pm 2) \times 10^{-33}$~cm$^6$s$^{-1}$ at 2.4~K. The stability of the ground Th ($^3$F$_2$) state, metastable Th ($^3$P$_0$) state, and vibrational excited ThO (X, $\nu=1$) state provides data on anisotropic interactions in new systems and opens up the possibility for further studies and experiments, including trapping.Physics
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Oliveira, de Araujo Michelle. "Super- et sous-radiance dans un nuage dilué d'atomes froids." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4200/document.
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Le problème de l'interaction de N atomes avec un faisceau laser et les modes du vide peut donner lieu à de nombreux phénomènes intéressants concernant l’émission spontanée de la lumière et sa propagation dans l’échantillon. Les effets coopératifs, par exemple, tels que la super- et la sous-radiance, sont des effets liés à la cohérence créée entre les atomes lorsqu'un photon est émis spontanément par un seul atome excité. La super-radiance peut être définie comme le renforcement de l'émission spontanée due à une interférence constructive de la lumière diffusée. Son homologue, la sous-radiance, est le piégeage d'une partie de la lumière restante en raison d'interférences destructives. Dans les atomes froids, certains travaux théoriques antérieurs prédisent et caractérisent ces deux effets coopératifs dans un nuage atomique large et diluée, dans le régime des faibles intensités et à grands désaccords du laser incident. Le modèle théorique est un modèle de dipôles couplés pour atomes à deux niveaux pilotés par un champ de faible intensité et dans l'approche scalaire. L'expérience consiste à mesurer les taux de d’décroissance super- et sous-radiants à partir de l’intensité temporelle émise après la coupure du laser incident en régime stationnaire. Notre schéma expérimental consiste en un piège magneto-optique d’atomes de rubidium 87 à grandes épaisseurs optiques à résonance. Un faisceau sonde excite les atomes proches de la raie D2. L’intensité émise est détectée par un détecteur de photons uniques dépourvu d’afterpulsing et une procédure d’étalonnage nous permet de déterminer l’épaisseur optique résonante du nuage et sa température. Dans ce travail, nous rapportons l’observation expérimentale de la super- et sous-radiance dans un grand nuage d’atomes froids. Pour la sous-radiance, le résultat principal est l’évolution linéaire du temps caractéristique avec l’épaisseur optique résonante du nuage et son indépendance du désaccord. Pour la super-radiance, on observe la super-radiance en dehors de la direction vers l’avant. Nous vérifions la validité de nos interprétations avec les prédictions du modèle de dipôles couplés. Finalement, nous discutons l’interaction entre la sous-radiance et le piégeage de radiation, ainsi que des prévisions théoriques concernant : la configuration d’un nuage phasé, pour contrôler l’émission de l’amplitude sousradiante ; et les effets de température, où la sous-radiance s’avère robuste dans une large gamme de températuresThe problem of the interaction of N atoms with a laser beam and vacuum modes can give rise to many interesting phenomena concerning the spontaneous emission of light and its propagation in the medium. The cooperative effects, for example, such as superadiance and subradiance, are effects related to the coherence created between the atoms when a photon is emitted spontaneously by a single excited atom. Superradiance can be defined as the enhancement of the spontaneous emission due to constructive interference of the scattered light. Its counterpart, subradiance, is the trapping of some remaining light due to destructive interference. In cold atoms, some previous theoretical works predict and characterize these two cooperative effects in a large and diluted atomic cloud, in the regime of low intensities and large detunings of the incident laser. The theoretical model is a coupled-dipole model for two-level atoms driven by a low-intensity field and in the scalar approach. The experiment consists in measuring the super- and subradiant decay rates from the temporal emitted intensity after the switch off of the incident laser in the steady state. Our experimental setup consists in a magneto-optical trap of rubidium 87 atoms at large resonant optical thicknesses. A probe beam excites the atoms close to the D2 line. The intensity emitted is detected by a single photon detector with no afterpulsing and a calibration procedure allows us to determine the resonant optical thickness of the cloud and its temperature. In this work, we report the experimental observation of super- and subradiance in a large cloud of cold atoms. For subradiance, the main result is the linear evolution of the characteristic time with the resonant optical thickness of the cloud and its independence of the detuning. For superradiance, we observe superradiance out of the forward direction. We verify the validity of our interpretations with the predictions of the coupled-dipole model. Finally, we discuss the interplay of subradiance and radiation trapping, as well as theoretical predictions for: a setup of a phased cloud, to control the subradiant amplitude emission; and temperature effects, where subradiance is shown to be robust in a large range of temperatures
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Burks, Sidney. "Towards A Quantum Memory For Non-Classical Light With Cold Atomic Ensembles." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00699270.
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Une mémoire quantique réversible permettant de stocker et relire de l'information quantique est une composante majeure dans la mise en œuvre de nombreux protocoles d'information quantique. Comme la lumière est un porteur de l'information quantique fiable sur des longues distances, et comme les atomes offrent la possibilité d'obtenir de longues durées de stockage, le recherche actuelle sur la création d'une mémoire quantique se concentre sur la transfert des fluctuations quantiques de la lumière sur des cohérences atomiques. Le travail réalisé durant cette thèse porte sur le développement d'une mémoire quantique pour la lumière comprimée, utilisant un ensemble d'atomes froids de Césium stock'es dans un piege magnéto-optique. Nos deux principaux objectifs étaient le développement d'une source de lumière non-classique, et le développement d'un milieu atomique pour le stockage de celle-ci. Tout d'abord, nous commençons par présenter la construction d'un oscillateur paramétrique optique qui utilise un cristal non-linéaire de PPKTP. Cet OPO fonctionne comme source d'états de vide comprime résonant avec la raie D2 du Césium. Nous caractérisons ces états grâce à une reconstruction par tomographie quantique, en utilisant une approche de vraisemblance maximale. Ensuite, nous examinons une nouvelle expérience qui nous permet d'utiliser comme milieu de stockage des atomes froids de Césium dans un piège magneto-optique récemment développé. Car cette expérience exige l'utilisation de nouveaux outils et techniques, nous discutons le développement de ceux-ci, et comment ils ont contribue à notre progression vers le stockage des états quantiques dans nos atomes des Césium, et finalement vers l'intrication de deux ensembles atomiques.
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Newell, Catherine A. "INELASTIC COLLISIONS IN COLD DIPOLAR GASES." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/30.
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Inelastic collisions between dipolar molecules, assumed to be trapped in a static electric field at cold (> 10−3K) temperatures, are investigated and compared with elastic collisions. For molecules with a Λ-doublet energy-level structure, a dipole moment arises because of the existence of two nearly degenerate states of opposite parity, and the collision of two such dipoles can be solved entirely analytically in the energy range of interest. Cross sections and rate constants are found to satisfy simple, universal formulas. In contrast, for molecules in a Σ electronic ground state, the static electric field induces a dipole moment in one of three rotational sublevels. Collisions between two rotor dipoles are calculated numerically; the results scale simply with molecule mass, rotational constant, dipole moment, and field strength.
It might be expected that any particles interacting only under the influence of the dipole-dipole interaction would show similar behavior; however, the most important and general result of this research is that at cold temperatures inelastic rate constants and cross sections for dipoles depend strongly upon the internal structure of the molecules. The most prominent difference between the Λ-doublet and rotor molecules is variation of the inelastic cross section with applied field strength. For Λ-doublet dipoles, cross sections decrease with increasing field strength. For rotor dipoles, cross sections increase proportionally with the square of field strength. Furthermore, the rate constants of the two types of molecules depend very differently on the angular orientations of the dipoles in the electric field.
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Gadge, Amruta. "A cold atom apparatus for the microscopy of thin membranes." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49881/.
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Ultracold atomic gases can be utilised as extremely sensitive probes of their surrounding environment. In particular, samples of ultracold atoms confined using chip-based microtraps are an ideal tool for mapping electric and magnetic field landscapes. Over the course of this thesis, a new experiment capable of performing surface microscopy using magnetically trapped clouds of cold rubidium-87 atoms has been built. The focus of the work is on the design and construction of the experimental system, which must incorporate many different aspects for manipulating thermal atomic gases, with a view to positioning them at sub-micron distances from special surfaces. This reduced atom-surface separation is necessary for implementing a high resolution, high sensitivity magnetic field sensor with cold atoms. Although current microfabrication techniques easily enable trapping at distances on the order of micrometres, several distance-dependent surface effects - such as the Casimir-Polder force, Johnson-Nyquist noise, and stray potentials - eventually impede magnetic trapping at the sub-micron level. These surface effects can greatly modify the confining potentials, which reduces the trap depth and consequently leads to an additional loss rate of atoms from the trap. We have explored the possibility of using special surfaces such as nano-membranes of silicon nitride and graphene, which have reduced atom- surface interactions, to enable trapping distances at the sub-micron level. A multilayer printed circuit board chip has been designed to form an initial magnetic trap and then transport the cloud of atoms to a desired location over the samples. This chip, along with various samples, is mounted on a custom-made electrical feedthrough designed to make connections to all conductor that are inside the vacuum chamber. The initial cloud of cold atoms can then be prepared in the central region of the chip and delivered to the location of the samples on either side. The experimental system is able to routinely capture over 10^8 rubidium-87 atoms at a temperature of 80 micro-Kelvin in a magneto-optical trap using a novel scheme of five laser beams. A method is demonstrated for enhancing the atom number in the magneto-optical traps by a factor of two by using laser beams with two slightly different frequencies. Atoms from the magneto-optical trap are then transferred to a purely magnetic trap formed by the wires on the printed circuit board chip. Time-dependent currents in the chip wires then create a dynamic potential, which is shown to successfully transport the atomic sample over a distance of 12 millimetre with minimal atom loss. This thesis describes the development of the apparatus in detail, along with careful characterisation of the cold cloud at various stages of the experimental sequence. Initial results on the long distance atom transport are presented. Finally, the experimental results of the two frequency magneto-optical trap for atom number improvement are discussed.
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Rehn, Magnus. "Experimental and Numerical Investigations of Ultra-Cold Atoms." Doctoral thesis, Umeå : Department of Physics, Umeå Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1453.
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Lefèvre, Grégoire. "Développement d’un interféromètre atomique en cavité pour le projet MIGA." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0063/document.
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Après plusieurs décennies de développement, l'interférométrie atomique est devenue un outil extrêmement performant pour mesurer des effets inertiels, tels que des accélérations et des rotations. De telles techniques sont maintenant envisagées pour une future génération de détecteurs d'ondes gravitationnelles afin de pousser les limites de l'état de l'art des détecteurs actuels. L'instrument MIGA (Matter-wave laser Interferometer Gravitation Antenna) couplera interférométrie atomique et optique pour étudier des perturbations du champ gravitationnel à basse fréquence (Hz et sub-Hz). Il consistera en un réseau de 3 interféromètres atomiques, simultanément interrogés par le champ électromagnétique résonnant au sein de deux cavités optiques de 150 m de long, en utilisant un ensemble d'impulsions de Bragg d'ordre π/2 - π - π/2. Des mesures gradiométriques permettront d'acquérir une forte immunité aux bruits sismique et newtonien, qui sont limitants pour les détecteurs terrestres optiques tels que LIGO et Virgo. Une expérience préliminaire est en développement au LP2N, à Talence (France), où un interféromètre est interrogé par deux cavités de 80 cm de long. Pour avoir une taille de faisceau suffisante afin d'interroger efficacement les atomes de 87Rb dans des cavités de cette longueur, nous utilisons une géométrie de cavité marginalement stable, constituée de deux miroirs plans situés à la focale d'une lentille biconvexe, où un mode gaussien de rayon de plusieurs mm peut résonnerAfter few decades of development, atom interferometry has become an extremely efficient tool for measuring inertial effects such as accelerations and rotations. Such techniques are now envisioned for a future generation of gravitational wave detectors to push further the limit of the current optical detectors. The Matter-Wave Laser Interferometer Gravitation Antenna (MIGA) instrument will couple atom and optical interferometry to study perturbations of the gravitational field at low-frequencies (Hz and sub-Hz). It will consist of an array of 3 atom interferometers, simultaneously interrogated by the light field resonating inside two 150 m long optical cavities, using a set of high order Bragg pulses π/2 - π - π/2. Gradiometric measurements allows a strong immunity to seismic and newtonian noises which limit optical ground-based detectors such as LIGO and Virgo. A preliminary experiment is being developed at the LP2N laboratory, in Talence (France), where a single atomic cloud is interrogated inside two 80 cm long cavities. In order to interrogate efficiently the 87Rb atoms, a gaussian beam with a radius of several mm resonating inside these cavities is required. This can be achieved by using a marginally stable cavity geometry, composed by two plane mirrors located in the focal planes of a biconvex lens
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Jiang, Kefeng. "Investigation of Stochastic Resonance in Directed Propagation of Cold Atoms." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1626991662334714.
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Schoene, Elizabeth A. 1979. "Cold atom control with an optical one-way barrier." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11067.
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xvi, 176 p. : ill. (some col.)The research presented in this dissertation aims to contribute to the field of atom optics via the implementation and demonstration of an all-optical one-way barrier for 87 Rb atoms--a novel tool for controlling atomic motion. This barrier--a type of atomic turnstile--transmits atoms traveling in one direction but hinders their passage in the other direction. We create the barrier with two laser beams, generating its unidirectional behavior by exploiting the two hyperfine ground states of 87 Rb. In particular, we judiciously choose the frequency of one beam to present a potential well to atoms in one ground state (the transmitting state) and a potential barrier to atoms in the other state (the reflecting state). The second beam optically pumps the atoms from the transmitting state to the reflecting state. A significant component of the experimental work presented here involves generating ultra-cold rubidium atoms for demonstrating the one-way barrier. To this end, we have designed and constructed a sophisticated 87 Rb cooling and trapping apparatus. This apparatus comprises an extensive ultra-high vacuum system, four home-built, frequency-stabilized diode laser systems, a high-power Yb:fiber laser, a multitude of supporting optics, and substantial timing and control electronics. This system allows us to cool and trap rubidium atoms at a temperature of about 30 μK. The results presented in this dissertation are summarized as follows. We successfully implemented a one-way barrier for neutral atoms and demonstrated its asymmetric nature. We used this new tool to compress the phase-space volume of an atomic sample and examined its significance as a physical realization of Maxwell's demon. We also demonstrated the robustness of the barrier's functionality to variations in several important experimental parameters. Lastly, we demonstrated the barrier's ability to cool an atomic sample, substantiating its potential application as a new cooling tool. This dissertation includes previously published coauthored material.
Committee in charge: Dr. Hailin Wang, Chair; Dr. Daniel A. Steck, Research Advisor; Dr. Jens U. Nockel; Dr. David M. Strom; Dr. Jeffrey A. Cina
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Muldoon, Cecilia. "Control and manipulation of cold atoms in optical tweezers." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:920933c8-441c-4d59-a4f4-87f8c799a820.
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The ability to address and manipulate individual information carriers in a deterministic, coherent, and scalable manner is a central theme in quantum information processing. Neutral atoms trapped by laser light are amongst the most promising candidates for storing and processing information in a quantum computer or simulator, so a scalable and flexible scheme for their control and manipulation is paramount. This thesis demonstrates a fast and versatile method to address and dynamically control the position (the motional degrees of freedom) of neutral atoms trapped in optical tweezers. The tweezers are generated by using the direct image of a Spatial Light Modulator (SLM) which can control and shape a large number of optical dipole-force traps. Trapped atoms adapt to any change in the potential landscape, such that one can re-arrange and randomly access individual sites within atom-trap arrays. A diffraction limited imaging system is used to map the intensity distribution of the SLM onto a cloud of cold atoms captured and cooled using a Magneto Optical Surface Trap (MOST).
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Pittner, Heiko. "The Production and Investigation of Cold Antihydrogen Atoms." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-36605.
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Hachtel, Andrew J. "Creation and Detection of a 1D Optical Lattice of 85Rb Atoms Using a Low-Cost Camera and Imaging System." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1407511483.
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Oldham, James Martin. "Combination of a cold ion and cold molecular source." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ef33adcb-609a-4329-b4d8-aca8a1c48661.
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This thesis describes the combination of two sources of cold atomic or molecular species which can be used to study a wide range of ion-molecule reactions. The challenges in forming these species and in determining the fate of reactive events are explored throughout. Reactions occur in a volume within a radio-frequency ion trap, in which ions have previously been cooled to sub-Kelvin temperatures. Ions are laser-cooled, with migration of ions slowed sufficiently to form a quasi-crystalline spheroidal structure, deemed a Coulomb crystal. Fluorescence emitted as a consequence of laser-cooling is detected; the subsequent fluorescence profiles are used to determine the number of ions in the crystal and, in combination with complementary simulations, the temperature of these ions. Motion imparted by trapping fields can be substantial and simulations are required to accurately determine collision energies. A beam of decelerated molecules is aimed at this stationary ion target. An ammonia seeded molecular beam enters a Stark decelerator, based on the original design of Meijer and co-workers. The decelerator uses time-varying electric fields to remove kinetic energy from the molecules, which exit at speeds down to 35 m/s. A fast-opening shutter and focussing elements are subsequently used to maximise the decelerated flux in the reaction volume while minimising undecelerated molecule transmission. Substantial fluxes of decelerated ammonia are obtained with narrow velocity distributions to provide a suitable source of reactant molecules. Combination of these two techniques permits studies of reactions between atomic ions and decelerated molecules that can be entirely state-specific. Changes in the Coulomb crystal fluorescence profile denote changes in the ion identities, the rate of these changes can be used to obtain rate constants. Determination of rate constants is even possible despite the fact that neither reactant nor product ions are directly observed. This work has studied reactions between sympathetically cooled Xe+ ions and guided ND3 and has obtained data consistent with prior studies. Determination of reactive events is complicated if ion identities can change without affecting the fluorescence profile, or if multiple reaction channels are possible. A range of spectroscopic techniques are discussed and considered in regards to determining rate constants and product identities. Pulsed axial excitation of trapped ions can follow rapid changes in average ion weights and subtle changes for small crystals. Time-of-flight mass spectrometry is also demonstrated using the trapping electrodes and is suitable for discrimination of ions formed within the trap.
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Burrows, Kathryn Alice. "Non-adiabatic losses from radio frequency dressed cold atom traps." Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/61380/.
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Cold atom traps are a promising tool for investigating and manipulating atomic behaviour. Radio frequency (RF) dressed cold atom traps allow high versatility of trapping potentials, which is important for potential applications, particularly in atom interferometry. This thesis investigates non-adiabatic spin flip transitions which can lead to losses of atoms from RF-dressed cold atom traps. We develop two models for the adiabatic potentials associated with RF-dressed traps, for the cases in which gravity does and doesn't have a significant effect. Within these two models we use first order perturbation theory to calculate decay rates for the number of dressed spin flip transitions per unit time. Our obtained decay rates are dependent on the atomic energy. For RF-dressed cold atom traps in which spin flip transitions lead to losses of atoms from the trap, we are able to predict ow non-adiabatic transitions decrease the trapped atom number. We achieve this by modelling the atomic distribution of energies for several different scenarios. The thesis concludes with a comparison to experimental data, including modelling how atomic energies are affected by noise in the currents generating the trapping magnetic fields.
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Kim, Soo Y. "Cold single atoms for cavity QED experiments." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26581.
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Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009.Committee Chair: Chapman, Michael; Committee Member: Citrin, David; Committee Member: Kennedy, T. A. Brian; Committee Member: Kuzmich, Alexander; Committee Member: Raman, Chandra. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Friedman, Melissa E. "Pulse shaping for broadband photoassociation of cold molecules." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:18d49cc2-9146-4ff8-b3b3-9e045bff039c.
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The development of the field of the science of ultra-cold matter has opened some exciting possibilities in exploring the quantum-mechanical processes which dominate matter interactions at the sub-microscopic scale. Although methods of cooling atoms are well established, molecular cooling is made difficult by molecules’ additional vibrational and rotational degrees of freedom. It was the goal of the research in this work to approach molecular cooling indirectly, by using broadband shaped-pulse photoassociation for the generation of tightly bound ultracold Rb2 molecules. The experiments towards this goal conducted by our group included a pumpdecay experiment to observe the generation of ground state singlet or triplet molecules. However, attempts to observe an increase in ground state population have been unsuccessful. A pump-probe study of wavepacket dynamics in the 5s+5p electronic state was conducted in order to determine the appropriate timing for the application of an additional pulse to dump population into the ground state. Although the attempt to observe wavepacket oscillations has been unsuccessful, pump-probe studies have yielded the observation of loosely bound excited state molecules as a result of the photoassociation pulse. These results are promising as a first stage in a fully coherent pump-dump approach to stabilisation into the lowest vibrational ground state. This thesis will provide an introduction and overview to the concerns involved in addressing the problem of molecular cooling and generation. Experimental techniques will be discussed including pulsed laser systems, optical parametric amplifi- cation, and the presentation of an original design for pulse shaping with an acoustooptic modulator. The emphasis of these discussions will be on the principles and operating procedures required for the use of these devices as home-built systems. The thesis will conclude with the results of pump-probe experiments utilising the pulse shaper as a spectral cutting device.
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Masella, Guido. "Exotic quantum phenomena in cold atomic gases : numerical approaches." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAF061.
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L'objectif principal de cette thèse est l'étude des propriétés à basse énergie et température de systèmes fortement corrélés de bosons interagissant via des potentiels à portée longue et étendue, et pertinentes pour la réalisation expérimentale avec des gaz atomiques froids. Cette étude est réalisée à l'aide d'une combinaison de techniques numériques, comme le Path Integral Montecarlo et de techniques analytiques. Le principal résultat de mon travail est la démonstration de l’existence d’une phase supersolide à bandes et d’une rare transition entre différents supersolides dans un modèle à interaction finie de bosons de coer dur sur un réseau carré. J'étudie également les scénarios hors d'équilibre de tels modèles via des quenches de température simulées. Enfin, j'étudie comment la restauration de l'extensibilité énergétique dans des systèmes en interaction à longue portée peut avoir une incidence profonde sur les propriétés de basse énergie dans la limite thermodynamiqueThe central aim of this thesis is the study of the low-energy and low-temperature properties of strongly correlated systems of bosonic particles interacting via finite- and long-range potentials, and relevant to experimental realization with cold atomic gases. This study is carried out with a combination of state-of-the-art numerical techniques such as Path Integral Monte Carlo and analytical techniques. The main result of my work is the demonstration of the existence of a stripe supersolid phase and of a rare transition between isotropic and anisotropic supersolids in a finite-range interacting model of hard-bosons on a square lattice. I also investigate the out-of-equilibrium scenarios of such models via simulated temperature quenches. Finally, I investigate how restoring energy extensivity in long-range interacting systems can have a profound incidence on the low-energy properties in the thermodynamic limit
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Gill, Christopher. "Simulating transport through quantum networks in the presence of classical noise using cold atoms." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7302/.
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In work towards the development and creation of practical quantum devices for use in quantum computing and simulation, the importance of long lived coherence is key to the advantages offered over classical systems. Isolation from environmental sources of decoherence is of integral importance to such platforms. Recent experiments of biological systems seem to indicate the existence of certain structures that utilise the decohering effects of their surrounding environments to enhance performance. In this thesis, we present a novel experimental set-up used to simulate the effect of decoherence-enhanced systems by mapping the energy level structure of laser cooled Rubidium 87 atoms interacting with electromagnetic fields to a quantum network of connected sites. Classical noise is controllably added to the states to create a tunable system to explore these effects. We present the design and implementation of the system, with results of several technical aspects, along with initial work on the effect of the applied noise on transport through the network. We present a key result that transport through the network is non-trivially enhanced by the presence of an optimum amplitude of noise, pointing to the interplay between the coherent nature of the quantum system and the decoherence provided by the noise.
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Forbes, Michael McNeil. "Fermionic superfluids : from cold atoms to high density QCD : gapless (breached pair) superfluidity and kaon condensation." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32299.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 189-198).
In this thesis, we explore aspects of fermionic superfluidity through a mean-field approximation. Our framework is extremely general, includes both pairing and Hartree-Fock contributions, and is derived rigorously from a variational principle. This framework allows us to analyze a wide range of fermionic systems. In this thesis, we shall consider two-species nonrelativistic atomic systems with various types of interactions, and relativistic QCD systems with 3 x 3 x 4 = 36 different quark degrees of freedom (3 colours, 3 flavours, and 4 relativistic degrees of freedom). We discuss properties of a new state of matter: gapless (Breached Pair) superfluidity, and include a summary of potential experimental realizations. We also present numerical results for a completely self-consistent approximation to the NJL model of high-density QCD and use these results to demonstrate a microscopic realization of kaon condensation. We describe how to match the mean-field approximation to the low-energy chiral effective theory of pseudo-Goldstone bosons, and we extract the numerical coefficients of the lowest order effective potential.
by Michael McNeil Forbes.
Ph.D.
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Hattermann, Helge [Verfasser], and József [Akademischer Betreuer] Fortágh. "Interfacing cold atoms and superconductors / Helge Hattermann ; Betreuer: József Fortágh." Tübingen : Universitätsbibliothek Tübingen, 2013. http://d-nb.info/1162844671/34.
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Sauer, Jacob A. "Cold Atom Manipulation for Quantum Computing and Control." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4809.
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Devices that exploit the properties of quantum mechanics for their operation can offer unique advantages over their classical counterparts. Interference of matter waves can be used to
dramatically increase the rotational sensitivity of gyroscopes. Complete control of the quantum evolution of a system could produce a new powerful computational device known as a quantum computer. Research into these technologies offers a deeper
understanding of quantum mechanics as well as exciting new insights into many other areas of science. Currently, a limiting factor in many quantum devices using neutral atoms is accurate motional control over the atoms. This thesis describes two recent advancements in neutral atom motional control using both magnetic and electromagnetic confining fields. Part I reports on the demonstration of the first storage ring for neutral atoms. This storage ring may one day provide the basis for the world's most
sensitive gyroscope. Part II describes the optical delivery of neutral atoms into the mode of a high-finesse cavity for applications in quantum computing and communication.
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Dauphin, Alexandre. "Cold atom quantum simulation of topological phases of matter." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209076.
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L'étude des phases de la matière est d'un intérêt fondamental en physique. La théorie de Landau, qui est le "modèle standard" des transitions de phases, caractérise les phases de la matière en termes des brisures de symétrie, décrites par un paramètre d'ordre local. Cette théorie a permis la description de phénomènes remarquables tels que la condensation de Bose-Einstein, la supraconductivité et la superfluidité.Il existe cependant des phases qui échappent à la description de Landau. Il s'agit des phases quantiques topologiques. Celles-ci constituent un nouveau paradigme et sont caractérisées par un ordre global défini par un invariant topologique. Ce dernier classe les objets ou systèmes de la manière suivante: deux objets appartiennent à la même classe topologique s'il est possible de déformer continument le premier objet en le second. Cette propriété globale rend le système robuste contre des perturbations locales telles que le désordre.
Les atomes froids constituent une plateforme idéale pour simuler les phases quantiques topologiques. Depuis l'invention du laser, les progrès en physique atomique et moléculaire ont permis un contrôle de la dynamique et des états internes des atomes. La réalisation de gaz quantiques,tels que les condensats de Bose-Einstein et les gaz dégénérés de Fermi, ainsi que la réalisation de réseaux optiques à l'aide de faisceaux lasers, permettent d'étudier ces nouvelles phases de la matière et de simuler aussi la physique du solide cristallin.
Dans cette thèse, nous nous concentrons sur l'etude d'isolants topologiques avec des atomes froids. Ces derniers sont isolants de volume mais possèdent des états de surface qui sont conducteurs, protégés par un invariant topologique. Nous traitons trois sujets principaux. Le premier sujet concerne la génération dynamique d'un isolant topologique de Mott. Ici, les interactions engendrent l'isolant topologique et ce, sans champ de jauge de fond. Le second sujet concerne la détection des isolants topologiques dans les expériences d'atomes froids. Nous proposons deux méthodes complémentaires pour caractériser celles-ci. Finalement, le troisième sujet aborde des thèmes au-delà de la définition standard d'isolant topologique. Nous avons d'une part proposé un algorithme efficace pour calculer la conductivité de Berry, la contribution topologique à la conductivité transverse lorsque l'énergie de Fermi se trouve dans une bande d'énergie. D'autre part, nous avons utilisé des méthodes pour caractériser les propriétés quantiques topologiques de systèmes non-périodiques.
L'étude des isolants topologiques dans les expériences d'atomes froids est un sujet de recherche récent et en pleine expansion. Dans ce contexte, cette thèse apporte plusieurs contributions théoriques pour la simulation de systèmes quantiques sur réseau avec des atomes froids.
Doctorat en Sciences
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Popp, Markus [Verfasser], J. I. [Akademischer Betreuer] Cirac, and Manfred [Akademischer Betreuer] Kleber. "Entanglement and Correlations in Cold Atomic Systems / Markus Popp. Gutachter: Manfred Kleber. Betreuer: Ignacio Cirac." München : Universitätsbibliothek der TU München, 2006. http://d-nb.info/1054310408/34.
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Dilyard, Ian Thomas. "Bidirectional and Unidirectional Ratcheting of Cold Atoms in a Dissipative 3D Optical Lattice." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1627007454969735.
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Bergkvist, Sylvan Sara. "Numerical studies of spin chains and cold atoms in optical lattices." Doctoral thesis, Stockholm, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4281.
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De, Palatis Michael V. "Production of cold barium monohalide ions." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50251.
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Ion traps are an incredibly versatile tool which have many applications throughout the physical sciences, including such diverse topics as mass spectrometry, precision frequency metrology, tests of fundamental physics, and quantum computing. In this thesis, experiments are presented which involve trapping and measuring properties of Th³⁺. Th³⁺ ions are of unique interest in part because they are a promising platform for studying an unusually low-lying nuclear transition in the 229Th nucleus which could eventually be used as an exceptional optical clock. Here, experiments to measure electronic lifetimes of Th³⁺ are described. A second experimental topic explores the production of sympathetically cooled molecular ions. The study of cold molecular ions has a number of applications, some of which include spectroscopy to aid the study of astrophysical objects, precision tests of quantum electrodynamics predictions, and the study of chemical reactions in the quantum regime. The experiments presented here involve the production of barium monohalide ions, BaX⁺ (X = F, Cl, Br). This type of molecular ion proves to be particularly promising for cooling to the rovibrational ground state. The method used for producing BaX⁺ ions involves reactions between cold, trapped Ba⁺ ions and neutral gas phase reactants at room temperature. The Ba⁺ ion reaction experiments presented in this thesis characterize these reactions for producing Coulomb crystals composed of laser cooled Ba⁺ ions and sympathetically cooled BaX⁺ ions.
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Langer, Stephan Markus. "Transport and real-time dynamics in one-dimensional quantum magnets and ultra-cold atomic gases." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-147217.
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Paris, Mandoki Asaf. "A single apparatus for the production of ultracold fermionic lithium and cold bosonic caesium gases." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/30601/.
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Ultracold mixture experiments hold the promise of providing new insights into many-body quantum systems as well as ultracold chemistry and few-body phenomena. The work presented in this thesis dealt with the construction of a new apparatus for the production and study of ultracold gases of fermionic lithium-6 and bosonic caesium-133. These isotopes offer a wide tunability in their interaction strength, both in inter-species and intra-species collisions, through magnetic Feshbach resonances. Additionally, the widely different resonance frequencies of lithium and caesium enables independent control of each of the species. With this apparatus, Bose-Einstein condensates (BEC) containing 10^4 lithium Feshbach molecules are routinely produced. The cooling system for caesium has been developed in parallel and important steps towards producing ultracold caesium gases have been made. An optical dipole trap has been loaded with 2x10^6 caesium atoms and evaporative cooling towards quantum degeneracy can now be pursued. Laser, vacuum, magnetic and control systems have been developed for the implementation of this experiment. Light produced with this laser system was used to laser cool atoms, create conservative dipole traps as well as to provide means of imaging atomic clouds. Additionally, a system to produce strong magnetic fields of up to 1400 G has been established in order to exploit the wide tunability in the atomic interactions. Software that was developed for the computerised control system facilitated the coordination of all the components involved in the experimental sequence. Measurements and calculations that showcase the functionality of relevant parts of the setup are presented in this thesis. In this experiment, lithium and caesium atoms are obtained from a novel type of Zeeman slower and are loaded into a magneto-optical trap (MOT). The system is capable of doing this independently for each of the atomic species as well as sequentially. After the MOT has been loaded with atoms, they are transferred into a conservative far-off-resonance optical dipole trap. By adjusting the interactions between atoms and lowering the depth of the dipole trap, efficient evaporative cooling of lithium was carried out from which a molecular BEC was obtained. Time-of-flight measurements were used to characterise the condensate and study its expansion dynamics.