263 research outputs found
Quantum optics with bosons and fermions
Atom optics, a field which takes much inspiration from traditional optics,
has advanced to the point that some of the fundamental experiments of quantum
optics, involving photon correlations, have found atomic analogs. We discuss
some recent experiments on atom bunching and anti-bunching as well as some
prospects for extending them to the field of many body physics.Comment: English version of "Optique atomique quantique : apr\`es les bosons,
les fermions
All optical cooling of K to Bose Einstein condensation
We report the all-optical production of Bose Einstein condensates (BEC) of
K atoms. We directly load atoms in a large volume
optical dipole trap from gray molasses on the D1 transition. We then apply a
small magnetic quadrupole field to polarize the sample before transferring the
atoms in a tightly confining optical trap. Evaporative cooling is finally
performed close to a Feshbach resonance to enhance the scattering length. Our
setup allows to cross the BEC threshold with atoms every 7s. As
an illustration of the interest of the tunability of the interactions we study
the expansion of Bose-Einstein condensates in the 1D to 3D crossover
Momentum-space atom correlations in a Mott insulator
We report on the investigation of the three-dimensional single-atom-resolved
distributions of bosonic Mott insulators in momentum-space. Firstly, we measure
the two-body and three-body correlations deep in the Mott regime, finding a
perfectly contrasted bunching whose periodicity reproduces the reciprocal
lattice. In addition, we show that the two-body correlation length is inversely
proportional to the in-trap size of the Mott state with a pre-factor in
agreement with the prediction for an incoherent state occupying a uniformly
filled lattice. Our findings indicate that the momentum-space correlations of a
Mott insulator at small tunnelling is that of a many-body ground-state with
Gaussian statistics. Secondly, in the Mott insulating regime with increasing
tunnelling, we extract the spectral weight of the quasi-particles from the
momentum density profiles. On approaching the transition towards a superfluid,
the momentum spread of the spectral weight is found to decrease as a result of
the increased mobility of the quasi-particles in the lattice. While the shapes
of the observed spectral weight agree with the ones predicted by perturbative
many-body calculations, the fitted mobilities are larger than the theoretical
ones. This discrepancy is similar to that previously reported on the
time-of-flight visibility.Comment: 13 pages, 10 figure
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
Guided Quasicontinuous Atom Laser
We report the first realization of a guided quasicontinuous atom laser by rf
outcoupling a Bose-Einstein condensate from a hybrid optomagnetic trap into a
horizontal atomic waveguide. This configuration allows us to cancel the
acceleration due to gravity and keep the de Broglie wavelength constant at 0.5
m during 0.1 s of propagation. We also show that our configuration,
equivalent to pigtailing an optical fiber to a (photon) semiconductor laser,
ensures an intrinsically good transverse mode matching.Comment: version published in Phys. Rev. Lett. 97, 200402 (2006
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
Anderson Localization of Expanding Bose-Einstein Condensates in Random Potentials
We show that the expansion of an initially confined interacting 1D
Bose-Einstein condensate can exhibit Anderson localization in a weak random
potential with correlation length \sigma_R. For speckle potentials the Fourier
transform of the correlation function vanishes for momenta k > 2/\sigma_R so
that the Lyapunov exponent vanishes in the Born approximation for k >
1/\sigma_R. Then, for the initial healing length of the condensate \xi >
\sigma_R the localization is exponential, and for \xi < \sigma_R it changes to
algebraic.Comment: published versioon (no significant change compared to last version
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