65 research outputs found
Spontaneous photon emission stimulated by two Bose condensates
We show that the phase difference of two overlapping ground state
Bose-Einstein condensates can effect the optical spontaneous emission rate of
excited atoms. Depending on the phase difference the atom stimulated
spontaneous emission rate can vary between zero and the rate corresponding to
all the ground state atoms in a single condensate. Besides giving control over
spontaneous emission this provides an optical method for detecting the
condensate phase difference. It differs from previous methods in that no light
fields are applied. Instead the light is spontaneously emitted when excited
atoms make a transition into either condensate.Comment: 14 pages, 2 postscript figures, Revtex. Corrections and significant
additions in revisio
Creation of vortices in a Bose-Einstein condensate by a Raman technique
We propose a method for taking a Bose-Einstein condensate in the ground trap
state simultaneously to a different atomic hyperfine state and to a vortex trap
state. This can be accomplished through a Raman scheme in which one of the two
copropagating laser beams has a higher-order Laguerre-Gaussian mode profile.
Coefficients relating the beam waist, pulse area, and trap potentials for a
complete transfer to the m = 1 vortex are calculated for a condensate in the
non-interacting and strongly interacting regimes.Comment: RevTex, 4 pages, 2 PostScript figure
Detection of vorticity in Bose-Einstein condensed gases by matter-wave interference
A phase-slip in the fringes of an interference pattern is an unmistakable
characteristic of vorticity. We show dramatic two-dimensional simulations of
interference between expanding condensate clouds with and without vorticity. In
this way, vortices may be detected even when the core itself cannot be
resolved.Comment: 3 pages, RevTeX, plus 6 PostScript figure
Macroscopic superpositions of Bose-Einstein condensates
We consider two dilute gas Bose-Einstein condensates with opposite velocities
from which a monochromatic light field detuned far from the resonance of the
optical transition is coherently scattered. In the thermodynamic limit, when
the relative fluctuations of the atom number difference between the two
condensates vanish, the relative phase between the Bose-Einstein condensates
may be established in a superposition state by detections of spontaneously
scattered photons, even though the condensates have initially well-defined atom
numbers. For a finite system, stochastic simulations show that the measurements
of the scattered photons lead to a randomly drifting relative phase and drive
the condensates into entangled superpositions of number states. This is because
according to Bose-Einstein statistics the scattering to an already occupied
state is enhanced.Comment: 18 pages, RevTex, 5 postscript figures, 1 MacBinary eps-figur
Reconstruction of the joint state of a two-mode Bose-Einstein condensate
We propose a scheme to reconstruct the state of a two-mode Bose-Einstein
condensate, with a given total number of atoms, using an atom interferometer
that requires beam splitter, phase shift and non-ideal atom counting
operations. The density matrix in the number-state basis can be computed
directly from the probabilities of different counts for various phase shifts
between the original modes, unless the beamsplitter is exactly balanced.
Simulated noisy data from a two-mode coherent state is produced and the state
is reconstructed, for 49 atoms. The error can be estimated from the singular
values of the transformation matrix between state and probability data.Comment: 4 pages (REVTeX), 5 figures (PostScript
Pumping two dilute gas Bose-Einstein condensates with Raman light scattering
We propose an optical method for increasing the number of atoms in a pair of
dilute gas Bose-Einstein condensates. The method uses laser-driven Raman
transitions which scatter atoms between the condensate and non-condensate atom
fractions. For a range of condensate phase differences there is destructive
quantum interference of the amplitudes for scattering atoms out of the
condensates. Because the total atom scattering rate into the condensates is
unaffected the condensates grow. This mechanism is analogous to that
responsible for optical lasing without inversion. Growth using macroscopic
quantum interference may find application as a pump for an atom laser.Comment: 4 pages, no figure
Non-destructive optical measurement of relative phase between two Bose condensates
We study the interaction of light with two Bose condensates as an open
quantum system. The two overlapping condensates occupy two different Zeeman
sublevels and two driving light beams induce a coherent quantum tunneling
between the condensates. We derive the master equation for the system. It is
shown that stochastic simulations of the measurements of spontaneously
scattered photons establish the relative phase between two Bose condensates,
even though the condensates are initially in pure number states. These
measurements are non-destructive for the condensates, because only light is
scattered, but no atoms are removed from the system. Due to the macroscopic
quantum interference the detection rate of photons depends substantially on the
relative phase between the condensates. This may provide a way to distinguish,
whether the condensates are initially in number states or in coherent states.Comment: 26 pages, RevTex, 8 postscript figures, 1 MacBinary eps-figur
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