18 research outputs found
Metropolis-Hastings thermal state sampling for numerical simulations of Bose-Einstein condensates
We demonstrate the application of the Metropolis-Hastings algorithm to
sampling of classical thermal states of one-dimensional Bose-Einstein
quasicondensates in the classical fields approximation, both in untrapped and
harmonically trapped case. The presented algorithm can be easily generalized to
higher dimensions and arbitrary trap geometry. For truncated Wigner simulations
the quantum noise can be added with conventional methods (half a quantum of
energy in every mode). The advantage of the presented method over the usual
analytical and stochastic ones lies in its ability to sample not only from
canonical and grand canonical distributions, but also from the generalized
Gibbs ensemble, which can help to shed new light on thermodynamics of
integrable systems.Comment: 13 pages, 4 figure
Atom interferometry with trapped Bose-Einstein condensates: Impact of atom-atom interactions
Interferometry with ultracold atoms promises the possibility of ultraprecise
and ultrasensitive measurements in many fields of physics, and is the basis of
our most precise atomic clocks. Key to a high sensitivity is the possibility to
achieve long measurement times and precise readout. Ultra cold atoms can be
precisely manipulated at the quantum level, held for very long times in traps,
and would therefore be an ideal setting for interferometry. In this paper we
discuss how the non-linearities from atom-atom interactions on one hand allow
to efficiently produce squeezed states for enhanced readout, but on the other
hand result in phase diffusion which limits the phase accumulation time. We
find that low dimensional geometries are favorable, with two-dimensional (2D)
settings giving the smallest contribution of phase diffusion caused by
atom-atom interactions. Even for time sequences generated by optimal control
the achievable minimal detectable interaction energy is on
the order of 0.001 times the chemical potential of the BEC in the trap. From
there we have to conclude that for more precise measurements with atom
interferometers more sophisticated strategies, or turning off the interaction
induced dephasing during the phase accumulation stage, will be necessary.Comment: 28 pages, 13 figures, extended and correcte