9 research outputs found
Occupation Statistics of a BEC for a Driven Landau-Zener Crossing
We consider an atomic Bose-Einstein condensate (BEC) loaded in a biased
double-well trap with tunneling rate and inter-atomic interaction . The
BEC is prepared such that all atoms are in the left well. We drive the
system by sweeping the potential difference between the two wells.
Depending on the interaction , and the sweep rate , we
distinguish three dynamical regimes: adiabatic, diabatic, and sudden, and
consider the occupation statistics of the final state. The analysis goes beyond
mean-field theory and is complemented by a semiclassical picture.Comment: 4 pages, 5 figure
Non-adiabatic pumping in an oscillating-piston model
We consider the prototypical "piston pump" operating on a ring, where a
circulating current is induced by means of an AC driving. This can be regarded
as a generalized Fermi-Ulam model, incorporating a finite-height moving wall
(piston) and non trivial topology (ring). The amount of particles transported
per cycle is determined by a layered structure of phase-space. Each layer is
characterized by a different drift velocity. We discuss the differences
compared with the adiabatic and Boltzmann pictures, and highlight the
significance of the "diabatic" contribution that might lead to a
counter-stirring effect.Comment: 6 pages, 4 figures, improved versio
Counting statistics in multiple path geometries and the fluctuations of the integrated current in a quantum stirring device
The amount of particles that are transported via a path of motion is
characterized by its expectation value and by its variance . We
analyze what happens if a particle has two optional paths available to get from
one site to another site, and in particular what is for the current
which is induced in a quantum stirring device. It turns out that coherent
splitting and the stirring effect are intimately related and cannot be
understood within the framework of the prevailing probabilistic theory.Comment: 11 pages, 2 figures, published version, Latex Eq# correcte