  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.
