242 research outputs found
Nonlinear atom-optical delta-kicked harmonic oscillator using a Bose-Einstein condensate
We experimentally investigate the atom-optical delta-kicked harmonic
oscillator for the case of nonlinearity due to collisional interactions present
in a Bose-Einstein condensate. A Bose condensate of rubidium atoms tightly
confined in a static harmonic magnetic trap is exposed to a one-dimensional
optical standing-wave potential that is pulsed on periodically. We focus on the
quantum anti-resonance case for which the classical periodic behavior is simple
and well understood. We show that after a small number of kicks the dynamics is
dominated by dephasing of matter wave interference due to the finite width of
the condensate's initial momentum distribution. In addition, we demonstrate
that the nonlinear mean-field interaction in a typical harmonically confined
Bose condensate is not sufficient to give rise to chaotic behavior.Comment: 4 pages, 3 figure
Weak dynamical localization in periodically kicked cold atomic gases
Quantum kicked rotor was recently realized in experiments with cold atomic
gases and standing optical waves. As predicted, it exhibits dynamical
localization in the momentum space. Here we consider the weak localization
regime concentrating on the Ehrenfest time scale. The later accounts for the
spread-time of a minimal wavepacket and is proportional to the logarithm of the
Planck constant. We show that the onset of the dynamical localization is
essentially delayed by four Ehrenfest times and give quantitative predictions
suitable for an experimental verification.Comment: 4 pages, 2 figure
Bose Einstein Condensate in a Box
Bose-Einstein condensates have been produced in an optical box trap. This
novel optical trap type has strong confinement in two directions comparable to
that which is possible in an optical lattice, yet produces individual
condensates rather than the thousands typical of a lattice. The box trap is
integrated with single atom detection capability, paving the way for studies of
quantum atom statistics.Comment: 4 pages, 5 figure
Decay by tunneling of Bosonic and Fermionic Tonks-Girardeau Gases
We study the tunneling dynamics of bosonic and fermionic Tonks-Girardeau
gases from a hard wall trap, in which one of the walls is substituted by a
delta potential. Using the Fermi-Bose map, the decay of the probability to
remain in the trap is studied as a function of both the number of particles and
the intensity of the end-cap delta laser. The fermionic gas is shown to be a
good candidate to study deviations of the non-exponential decay of the
single-particle type, whereas for the bosonic case a novel regime of
non-exponential decay appears due to the contributions of different resonances
of the trap
Quantum and classical echoes in scattering systems described by simple Smale horseshoes
We explore the quantum scattering of systems classically described by binary
and other low order Smale horseshoes, in a stage of development where the
stable island associated with the inner periodic orbit is large, but chaos
around this island is well developed. For short incoming pulses we find
periodic echoes modulating an exponential decay over many periods. The period
is directly related to the development stage of the horseshoe. We exemplify our
studies with a one-dimensional system periodically kicked in time and we
mention possible experiments.Comment: 7 pages with 6 reduced quality figures! Please contact the authors
([email protected]) for an original good quality pre-prin
Dynamics of a Tonks-Girardeau gas released from a hard-wall trap
We study the expansion dynamics of a Tonks-Girardeau gas released from a hard
wall trap. Using the Fermi-Bose map, the density profile is found analytically
and shown to differ from that one of a classical gas in the microcanonical
ensemble even at macroscopic level, for any observation time larger than a
critical time. The relevant time scale arises as a consequence of
fermionization.Comment: 4 pages, 6 figure
Single-Photon Molecular Cooling
We propose a general method to cool the translational motion of molecules.
Our method is an extension of single photon atomic cooling which was
successfully implemented in our laboratory. Requiring a single event of
absorption followed by a spontaneous emission, this method circumvents the need
for a cycling transition and can be applied to any paramagnetic or polar
molecule. In our approach, trapped molecules would be captured near their
classical turning points in an optical dipole or RF-trap following an
irreversible transition process
Current relaxation in nonlinear random media
We study the current relaxation of a wave packet in a nonlinear random sample
coupled to the continuum and show that the survival probability decays as . For intermediate times , the exponent
satisfies a scaling law where is
the nonlinearity strength and is the localization length of the
corresponding random system with . For and we find a universal decay with which is a signature of the
{\it nonlinearity-induced delocalization}. Experimental evidence should be
observable in coupled nonlinear optical waveguides.Comment: revised version, PRL in press, 4 pages, 4 figs (fig 3 with reduced
quality
Using Cold Atoms to Measure Neutrino Mass
We propose a beta decay experiment based on a sample of ultracold atomic
tritium. These initial conditions enable detection of the helium ion in
coincidence with the beta. We construct a two-dimensional fit incorporating
both the shape of the beta-spectrum and the direct reconstruction of the
neutrino mass peak. We present simulation results of the feasible limits on the
neutrino mass achievable in this new type of tritium beta-decay experiment.Comment: 10 pages, 5 figure
Spatial nonlocal pair correlations in a repulsive 1D Bose gas
We analytically calculate the spatial nonlocal pair correlation function for
an interacting uniform 1D Bose gas at finite temperature and propose an
experimental method to measure nonlocal correlations. Our results span six
different physical realms, including the weakly and strongly interacting
regimes. We show explicitly that the characteristic correlation lengths are
given by one of four length scales: the thermal de Broglie wavelength, the mean
interparticle separation, the healing length, or the phase coherence length. In
all regimes, we identify the profound role of interactions and find that under
certain conditions the pair correlation may develop a global maximum at a
finite interparticle separation due to the competition between repulsive
interactions and thermal effects.Comment: Final published version, modified titl
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