153 research outputs found
Collective atomic recoil motion in short-pulse multi-matter-optical wave mixing
An analytical perturbation theory of short-pulse, matter-wave superradiant
scatterings is presented. We show that Bragg resonant enhancement is
incapacitated and both positive and negative order scatterings contribute
equally. We further show that propagation gain is small and scattering events
primarily occur at the end of the condensate where the generated field has
maximum strength, thereby explaining the apparent ``asymmetry" in the scattered
components with respect to the condensate center. In addition, the generated
field travels near the speed of light in a vacuum, resulting in significant
spontaneous emission when the one-photon detuning is not sufficiently large.
Finally, we show that when the excitation rate increases, the generated-field
front-edge-steepening and peak forward-shifting effects are due to depletion of
the ground state matter wave.Comment: This manuscript was submitted for publication in Nov., 200
Two point correlations of a trapped interacting Bose gas at finite temperature
We develop a computationally tractable method for calculating correlation
functions of the finite temperature trapped Bose gas that includes the effects
of s-wave interactions. Our approach uses a classical field method to model the
low energy modes and treats the high energy modes using a Hartree-Fock
description. We present results of first and second order correlation
functions, in position and momentum space, for an experimentally realistic
system in the temperature range of to . We also characterize
the spatial coherence length of the system. Our theory should be applicable in
the critical region where experiments are now able to measure first and second
order correlations.Comment: 9 pages, 4 figure
Imaging the phase of an evolving Bose-Einstein condensate wavefunction
We demonstrate a spatially resolved autocorrelation measurement with a
Bose-Einstein condensate (BEC) and measure the evolution of the spatial profile
of its quantum mechanical phase. Upon release of the BEC from the magnetic
trap, its phase develops a form that we measure to be quadratic in the spatial
coordinate. Our experiments also reveal the effects of the repulsive
interaction between two overlapping BEC wavepackets and we measure the small
momentum they impart to each other
Elastic scattering loss of atoms from colliding Bose-Einstein condensate wavepackets
Bragg diffraction of atoms by light waves has been used to create high
momentum components in a Bose-Einstein condensate. Collisions between atoms
from two distinct momentum wavepackets cause elastic scattering that can remove
a significant fraction of atoms from the wavepackets and cause the formation of
a spherical shell of scattered atoms. We develop a slowly varying envelope
technique that includes the effects of this loss on the condensate dynamics
described by the Gross-Pitaevski equation. Three-dimensional numerical
calculations are presented for two experimental situations: passage of a moving
daughter condensate through a non-moving parent condensate, and four-wave
mixing of matter waves.Comment: Phys. Rev. Lett, in pres
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