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Search Results: 1 - 10 of 92664 matches for " Christoph I. Westbrook "
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The Hanbury Brown Twiss effect for atomic matter waves
Christoph I Westbrook,Denis Boiron
Physics , 2010,
Abstract: This paper discusses our recent work on developing the matter wave analogs to the Hanbury Brown Twiss experiment. We discuss experiments using cold atoms, both bosons and fermions, both coherent and incoherent. Simple concepts from classical and quantum optics suffice to understand most of the results, but the ideas can also be traced back to the work of Einstein on the thermodynamics of Bose gases.
Atom chips and one-dimensional Bose gases
Isabelle Bouchoule,N. J. Van Druten,Christoph I. Westbrook
Physics , 2009,
Abstract: In this review article, we describe the studies of 1D gases realised on atom-chip experiments.
Atom-photon interactions in a system of coupled cavities
Abdelkrim El Amili,Sébastien Gleyzes,Christoph I Westbrook
Physics , 2012,
Abstract: We give a theoretical treatment of single atom detection in an compound, optical micro cavity. The cavity consists of a single mode semiconductor waveguide with a gap to allow atoms to interact with the optical field in the cavity. Optical losses, both in the semiconductor and induced by the gap are considered and we give an estimate of the cavity finesse. We also compute the cooperativity parameter and show how it depends on the gap width and cavity length. Maximization of the cooperativity does not always correspond to maximization of the coupling.
Roughness suppression via rapid current modulation on an atom chip
Jean-Baptiste Trebbia,Carlos Leonardo Garrido Alzar,Ronald Cornelussen,Christoph I. Westbrook,Isabelle Bouchoule
Physics , 2007,
Abstract: We present a method to suppress the potential roughness of a wire-based, magnetic atom guide: modulating the wire current at a few tens of kHz, the potential roughness, which is proportional to the wire current, averages to zero. Using ultra-cold $^{87}{\rm Rb}$ clouds, we show experimentally that modulation reduces the roughness by at least of a factor five without measurable heating or atom loss. This roughness suppression results in a dramatic reduction of the damping of center of mass oscillations.
Observations of density fluctuations in an elongated Bose gas: ideal gas and quasi-condensate regimes
Jerome Esteve,Jean-Baptiste Trebbia,Thorsten Schumm,Alain Aspect,Christoph I. Westbrook,Isabelle Bouchoule
Physics , 2005, DOI: 10.1103/PhysRevLett.96.130403
Abstract: We report in situ measurements of density fluctuations in a quasi one dimensional Bose gas at thermal equilibrium in an elongated harmonic trap. We observe an excess of fluctuations compared to the shot noise level expected for uncorrelated atoms. At low atomic density, the measured excess is in good agreement with the expected bunching for an ideal Bose gas. At high density, the measured fluctuations are strongly reduced compared to the ideal gas case. We attribute this reduction to repulsive interatomic interactions. The data are compared with a calculation for an interacting Bose gas in the quasi-condensate regime.
Experimental evidence for the breakdown of a Hartree-Fock approach in a weakly interacting Bose gas
Jean-Baptiste Trebbia,Jér?me Estève,Christoph I. Westbrook,Isabelle Bouchoule
Physics , 2006, DOI: 10.1103/PhysRevLett.97.250403
Abstract: We study the formation of a quasi-condensate in a nearly one dimensional, weakly interacting trapped atomic Bose gas. We show that a Hartree Fock (mean-field) approach fails to explain the presence of the quasi-condensate in the center of the cloud: the quasi-condensate appears through an interaction-driven cross-over and not a saturation of the excited states. Numerical calculations based on Bogoliubov theory give an estimate of the cross-over density in agreement with experimental results.
Theory for a Hanbury Brown Twiss experiment with a ballistically expanding cloud of cold atoms
Jose Viana Gomes,Aurélien Perrin,Martijn Schellekens,Denis Boiron,Christoph I. Westbrook,Michael Belsley
Physics , 2006, DOI: 10.1103/PhysRevA.74.053607
Abstract: We have studied one-body and two-body correlation functions in a ballistically expanding, non-interacting atomic cloud in the presence of gravity. We find that the correlation functions are equivalent to those at thermal equilibrium in the trap with an appropriate rescaling of the coordinates. We derive simple expressions for the correlation lengths and give some physical interpretations. Finally a simple model to take into account finite detector resolution is discussed.
An atomic Hong-Ou-Mandel experiment
Raphael Lopes,Almazbek Imanaliev,Alain Aspect,Marc Cheneau,Denis Boiron,Christoph I. Westbrook
Physics , 2015, DOI: 10.1038/nature14331
Abstract: The celebrated Hong, Ou and Mandel (HOM) effect is one of the simplest illustrations of two-particle interference, and is unique to the quantum realm. In the original experiment, two photons arriving simultaneously in the input channels of a beam-splitter were observed to always emerge together in one of the output channels. Here, we report on the realisation of a closely analogous experiment with atoms instead of photons. This opens the prospect of testing Bell's inequalities involving mechanical observables of massive particles, such as momentum, using methods inspired by quantum optics, with an eye on theories of the quantum-to-classical transition. Our work also demonstrates a new way to produce and benchmark twin-atom pairs that may be of interest for quantum information processing and quantum simulation.
Microwave-stimulated Raman adiabatic passage in a Bose-Einstein condensate on an atom chip
Matthieu Dupont-Nivet,Mathias Casiulis,Théo Laudat,Christoph I. Westbrook,Sylvain Schwartz
Physics , 2015, DOI: 10.1103/PhysRevA.91.053420
Abstract: We report the achievement of stimulated Raman adiabatic passage (STIRAP) in the microwave frequency range between internal states of a Bose-Einstein condensate (BEC) magnetically trapped in the vicinity of an atom chip. The STIRAP protocol used in this experiment is robust to external perturbations as it is an adiabatic transfer, and power-efficient as it involves only resonant (or quasi-resonant) processes. Taking into account the effect of losses and collisions in a non-linear Bloch equations model, we show that the maximum transfer efficiency is obtained for non-zero values of the one- and two-photon detunings, which is confirmed quantitatively by our experimental measurements.
The 2nd order coherence of superradiance from a Bose--Einstein condensate
Raphael Lopes,Almazbek Imanaliev,Marie Bonneau,Josselin Ruaudel,Marc Cheneau,Denis Boiron,Christoph I Westbrook
Physics , 2013, DOI: 10.1103/PhysRevA.90.013615
Abstract: We have measured the 2-particle correlation function of atoms from a Bose--Einstein condensate participating in a superradiance process, which directly reflects the 2nd order coherence of the emitted light. We compare this correlation function with that of atoms undergoing stimulated emission. Whereas the stimulated process produces correlations resembling those of a coherent state, we find that superradiance, even in the presence of strong gain, shows a correlation function close to that of a thermal state, just as for ordinary spontaneous emission.
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