113 research outputs found
Continuous Observation of Interference Fringes from Bose Condensates
We use continuous measurement theory to describe the evolution of two Bose
condensates in an interference experiment. It is shown how the system evolves
in a single run of the experiment into a state with a fixed relative phase,
while the total gauge symmetry remains unbroken. Thus, an interference pattern
is exhibited without violating atom number conservation.Comment: 4 pages, Postscrip
Output of a pulsed atom laser
We study the output properties of a pulsed atom laser consisting of an
interacting Bose-Einstein condensate (BEC) in a magnetic trap and an additional
rf field transferring atoms to an untrapped Zeeman sublevel. For weak output
coupling we calculate the dynamics of the decaying condensate population, of
its chemical potential and the velocity of the output atoms analytically.Comment: 4 pages, RevTeX. Full ps file available on
http://mpqibmr1.mpq.mpg.de:5000/~man
The linewidth of a non-Markovian atom laser
We present a fully quantum mechanical treatment of a single mode atom laser
including pumping and output coupling. By ignoring atom-atom interactions, we
have solved this model without making the Born-Markov approximation. We find
substantially less gain narrowing than is predicted under that approximation.Comment: 4 pages, 1 encapsulated postscript figur
Spatial coherence and density correlations of trapped Bose gases
We study first and second order coherence of trapped dilute Bose gases using
appropriate correlation functions. Special attention is given to the discussion
of second order or density correlations. Except for a small region around the
surface of a Bose-Einstein condensate the correlations can be accurately
described as those of a locally homogeneous gas with a spatially varying
chemical potential. The degrees of first and second order coherence are
therefore functions of temperature, chemical potential, and position. The
second order correlation function is governed both by the tendency of bosonic
atoms to cluster and by a strong repulsion at small distances due to atomic
interactions. In present experiments both effects are of comparable magnitude.
Below the critical temperature the range of the bosonic correlation is affected
by the presence of collective quasi-particle excitations. The results of some
recent experiments on second and third order coherence are discussed. It is
shown that the relation between the measured quantities and the correlation
functions is much weaker than previously assumed.Comment: RevTeX, 25 pages with 7 Postscript figure
Partially coherent matter wave and its evolution
The evolution and propagation of a partially coherent matter wave (PCMW) is
investigated theoretically by the correlation function method. The ABCD matrix
formalism previously used for a fully coherent matter wave is extended to the
PCMW domain. A new ABCD law is derived, using a tensor method to describe the
evolution of a PCMW. An analytical solution of the first-order correlation
function is obtained that makes the propagation and evolution of a PCMW very
simple and clear. As an example, the propagation of a PCMW in a gravitational
field is calculated numerically.Comment: 15 pages, 4 figure
Quantum measures for density correlations in optical lattices
The density-density correlation profiles obtained superimposing absorption
images from atomic clouds freely expanding after the release of the confining
optical lattice can be theoretically described in terms of a generalized
quantum measure based on coherent-like states. We show that the corresponding
density patterns differ in a testable way from those computed using standard
many-body mean values, usually adopted in fitting experimental data.Comment: LaTeX, 14 page
Enhancing capacity of coherent optical information storage and transfer in a Bose-Einstein condensate
Coherent optical information storage capacity of an atomic Bose-Einstein
condensate is examined. Theory of slow light propagation in atomic clouds is
generalized to short pulse regime by taking into account group velocity
dispersion. It is shown that the number of stored pulses in the condensate can
be optimized for a particular coupling laser power, temperature and interatomic
interaction strength. Analytical results are derived for semi-ideal model of
the condensate using effective uniform density zone approximation. Detailed
numerical simulations are also performed. It is found that axial density
profile of the condensate protects the pulse against the group velocity
dispersion. Furthermore, taking into account finite radial size of the
condensate, multi-mode light propagation in atomic Bose-Einstein condensate is
investigated. The number of modes that can be supported by a condensate is
found. Single mode condition is determined as a function of experimentally
accessible parameters including trap size, temperature, condensate number
density and scattering length. Quantum coherent atom-light interaction schemes
are proposed for enhancing multi-mode light propagation effects.Comment: 12pages. Laser Physics, in pres
Propagation of Raman-matched laser pulses through a Bose-Einstein condensate
We investigate the role of non-uniform spatial density profiles of trapped
atomic Bose-Einstein condensates in the propagation of Raman-matched laser
pulses under conditions for electromagnetically induced transparency (EIT). We
find that the sharp edged axial density profile of an interacting condensate
(due to a balance between external trap and repulsive atomic interaction) is
advantageous for obtaining ultra slow averaged group velocities. Our results
are in good quantitative agreement with a recent experiment report [Nature {\bf
397}, 594 (1999)].Comment: 19 pages, 11 figures, to be published in Opt. Commu
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