Transport of ultracold Bose gases beyond the Gross-Pitaevskii description

TL;DR

This paper investigates atom-laser-like transport of ultracold Bose gases in waveguides beyond mean-field theory, revealing how time-dependent flow causes condensate depletion and phase coherence loss.

Contribution

It develops a microscopic quantum model using Hartree-Fock-Bogoliubov approximation to study transport beyond Gross-Pitaevskii theory in complex structures.

Findings

Time-dependent flow correlates with condensate depletion.

Transport through disordered waveguides shows loss of phase coherence.

Model captures microscopic depletion dynamics.

Abstract

We explore atom-laser-like transport processes of ultracold Bose-condensed atomic vapors in mesoscopic waveguide structures beyond the Gross-Pitaevskii mean-field theory. Based on a microscopic description of the transport process in the presence of a coherent source which models the outcoupling from a reservoir of perfectly Bose-Einstein condensed atoms, we derive a system of coupled quantum evolution equations that describe the dynamics of a dilute condensed Bose gas in the framework of the Hartree-Fock-Bogoliubov approximation. We apply this method to study the transport of dilute Bose gases through an atomic quantum dot and through waveguides with disorder. Our numerical simulations reveal that the onset of an explictly time-dependent flow corresponds to the appearance of strong depletion of the condensate on the microscopic level and leads to a loss of global phase coherence.