7,268 research outputs found
Incoherence of Bose-Einstein condensates at supersonic speeds due to quantum noise
We calculate the effect of quantum noise in supersonic transport of
Bose-Einstein condensates. When an obstacle obstructs the flow of atoms,
quantum fluctuations cause atoms to be scattered incoherently into random
directions. This suppresses the propagation of Cherenkov radiation, creating
quantum turbulence and a crescent of incoherent atoms around the obstacle. We
observe similar dynamics if the BEC is stirred by a laser beam: crescents of
incoherent atoms are emitted from the laser's turning-points. Finally, we
investigate supersonic flow through a disordered potential, and find that the
quantum fluctuations generate an accumulation of incoherent atoms as the
condensate enters the disorder.Comment: 6 pages, 5 figure
Disruption of reflecting Bose-Einstein condensates due to inter-atomic interactions and quantum noise
We perform fully three-dimensional simulations, using the truncated Wigner
method, to investigate the reflection of Bose-Einstein condensates from abrupt
potential barriers. We show that the inter-atomic interactions can disrupt the
internal structure of a cigar-shaped cloud with a high atom density at low
approach velocities, damping the center-of-mass motion and generating vortices.
Furthermore, by incorporating quantum noise we show that scattering halos form
at high approach velocities, causing an associated condensate depletion. We
compare our results to recent experimental observations.Comment: 5 figure
Non-equilibrium dynamics: Studies of reflection of Bose-Einstein condensates
The study of the non-equilibrium dynamics in Bose-Einstein condensed gases
has been dominated by the zero-temperature, mean field Gross-Pitaevskii
formalism. Motivated by recent experiments on the reflection of condensates
from silicon surfaces, we revisit the so-called {\em classical field}
description of condensate dynamics, which incorporates the effects of quantum
noise and can also be generalized to include thermal effects. The noise is
included in a stochastic manner through the initial conditions. We show that
the inclusion of such noise is important in the quantitative description of the
recent reflection experiments
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