617 research outputs found
A Waveguide for Bose-Einstein Condensates
We report on the creation of Bose-Einstein condensates of Rb in a
specially designed hybrid, dipole and magnetic trap. This trap naturally allows
the coherent transfer of matter waves into a pure dipole potential waveguide
based on a doughnut beam. Specifically, we present studies of the coherence of
the ensemble in the hybrid trap and during the evolution in the waveguide by
means of an autocorrelation interferometer scheme. By monitoring the expansion
of the ensemble in the waveguide we observe a mean field dominated acceleration
on a much longer time scale than in the free 3D expansion. Both the
autocorrelation interference and the pure expansion measurements are in
excellent agreement with theoretical predictions of the ensemble dynamics
Second Order Correlation Function of a Phase Fluctuating Bose-Einstein Condensate
The coherence properties of phase fluctuating Bose-Einstein condensates are
studied both theoretically and experimentally. We derive a general expression
for the N-particle correlation function of a condensed Bose gas in a highly
elongated trapping potential. The second order correlation function is analyzed
in detail and an interferometric method to directly measure it is discussed and
experimentally implemented. Using a Bragg diffraction interferometer, we
measure intensity correlations in the interference pattern generated by two
spatially displaced copies of a parent condensate. Our experiment demonstrates
how to characterize the second order correlation function of a highly elongated
condensate and to measure its phase coherence length.Comment: 22 pages, 5 figure
Evidence of Luttinger liquid behavior in one-dimensional dipolar quantum gases
The ground state and structure of a one-dimensional Bose gas with dipolar
repulsions is investigated at zero temperature by a combined Reptation Quantum
Monte Carlo (RQMC) and bosonization approach. A non trivial Luttinger-liquid
behavior emerges in a wide range of intermediate densities, evolving into a
Tonks-Girardeau gas at low density and into a classical quasi-ordered state at
high density. The density dependence of the Luttinger exponent is extracted
from the numerical data, providing analytical predictions for observable
quantities, such as the structure factor and the momentum distribution. We
discuss the accessibility of such predictions in current experiments with
ultracold atomic and molecular gases.Comment: 4 pages, 3 EPS figures, Revtex
Phase Fluctuations in Bose-Einstein Condensates
We demonstrate the existence of phase fluctuations in elongated Bose-Einstein
Condensates (BECs) and study the dependence of those fluctuations on the system
parameters. A strong dependence on temperature, atom number, and trapping
geometry is observed. Phase fluctuations directly affect the coherence
properties of BECs. In particular, we observe instances where the phase
coherence length is significantly smaller than the condensate size. Our method
of detecting phase fluctuations is based on their transformation into density
modulations after ballistic expansion. An analytic theory describing this
transformation is developed.Comment: 11 pages, 7 figure
Characterization and control of phase fluctuations in elongated Bose-Einstein condensates
Quasi one dimensional Bose-Einstein condensates (BECs) in elongated traps
exhibit significant phase fluctuations even at very low temperatures. We
present recent experimental results on the dynamic transformation of phase
fluctuations into density modulations during time-of-flight and show the
excellent quantitative agreement with the theoretical prediction. In addition
we confirm that under our experimental conditions, in the magnetic trap density
modulations are strongly suppressed even when the phase fluctuates. The paper
also discusses our theoretical results on control of the condensate phase by
employing a time-dependent perturbation. Our results set important limitations
on future applications of BEC in precision atom interferometry and atom optics,
but at the same time suggest pathways to overcome these limitations.Comment: 9 pages, 7 figure
Исследование и сравнительный анализ различных компоновок по характеру влияния на транспортирование шлама
Recommended from our members
Berkeley Seismological Laboratory Seismic Moment Tensor Report for the August 6, 2007 M3.9 Seismic event in central Utah
We have performed a complete moment tensor analysis of the seismic event, which occurred on Monday August 6, 2007 at 08:48:40 UTC 21 km from Mt.Pleasant, Utah. In our analysis we utilized complete three-component seismic records recorded by the USArray, University of Utah, and EarthScope seismic arrays. The seismic waveform data was integrated to displacement and filtered between 0.02 to 0.10 Hz following instrument removal. We used the Song et al. (1996) velocity model to compute Green's functions used in the moment tensor inversion. A map of the stations we used and the location of the event is shown in Figure 1. In our moment tensor analysis we assumed a shallow source depth of 1 km consistent with the shallow depth reported for this event. As shown in Figure 2 the results point to a source mechanism with negligible double-couple radiation and is composed of dominant CLVD and implosive isotropic components. The total scalar seismic moment is 2.12e22 dyne cm corresponding to a moment magnitude (Mw) of 4.2. The long-period records are very well matched by the model (Figure 2) with a variance reduction of 73.4%. An all dilational (down) first motion radiation pattern is predicted by the moment tensor solution, and observations of first motions are in agreement
- …