100 research outputs found
The Hanbury Brown Twiss effect for atomic matter waves
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.Comment: also available at http://pos.sissa.it
Microwave-stimulated Raman adiabatic passage in a Bose-Einstein condensate on an atom chip
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
An atomic Hong-Ou-Mandel experiment
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
A study of atom localization in an optical lattice by analysis of the scattered light
We present an experimental study of a four beam optical lattice using the
light scattered by the atoms in the lattice. We use both intensity correlations
and observations of the transient behavior of the scattering when the lattice
is suddenly switched on. We compare results for 3 different configurations of
the optical lattice. We create situations in which the Lamb-Dicke effect is
negligible and show that, in contrast to what has been stated in some of the
literature, the damping rate of the 'coherent' atomic oscillations can be much
smaller than the inelastic photon scattering rate.Comment: An old pape
Tunable source of correlated atom beams
We use a one-dimensional optical lattice to modify the dispersion relation of
atomic matter waves. Four-wave mixing in this situation produces atom pairs in
two well defined beams. We show that these beams present a narrow momentum
correlation, that their momenta are precisely tunable, and that this pair
source can be operated both in the regime of low mode occupancy and of high
mode occupancy
Experimental study of the role of trap symmetry in an atom-chip interferometer above the Bose-Einstein condensation threshold
We report the experimental study of an atom-chip interferometer using
ultracold rubidium 87 atoms above the Bose-Einstein condensation threshold. The
observed dependence of the contrast decay time with temperature and with the
degree of symmetry of the traps during the interferometer sequence is in good
agreement with theoretical predictions published in [Dupont-Nivet et al., NJP
18, 113012 (2016)]. These results pave the way for precision measurements with
trapped thermal atoms.Comment: 11 pages, 4 figure
An acoustic analog to the dynamical Casimir effect in a Bose-Einstein condensate
We have realized an acoustic analog to the Dynamical Casimir effect. The
density of a trapped Bose-Einstein condensate is modulated by changing the trap
stiffness. We observe the creation of correlated excitations with equal and
opposite momenta, and show that for a well defined modulation frequency, the
frequency of the excitations is half that of the trap modulation frequency.Comment: Includes supplemental informatio
Anisotropy in s-wave Bose-Einstein condensate collisions and its relationship to superradiance
We report the experimental realization of a single-species atomic four-wave
mixing process with BEC collisions for which the angular distribution of
scattered atom pairs is not isotropic, despite the collisions being in the
-wave regime. Theoretical analysis indicates that this anomalous behavior
can be explained by the anisotropic nature of the gain in the medium. There are
two competing anisotropic processes: classical trajectory deflections due to
the mean-field potential, and Bose enhanced scattering which bears similarity
to super-radiance. We analyse the relative importance of these processes in the
dynamical buildup of the anisotropic density distribution of scattered atoms,
and compare to optically pumped super-radiance.Comment: 13 pages, 10 figures, added a fuller discussion of timescales,
otherwise some minor changes in the text and the formatting of Figures 5-
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