We examine the connection between the dwell time of a quantum particle in a region of space and flux-flux correlations at the boundaries. It is shown that the first and second moments of a flux-flux correlation function which generalizes a previous p
roposal by Pollak and Miller [E. Pollak and W. H. Miller, Phys. Rev. Lett. {bf 53}, 115 (1984)], agree with the corresponding moments of the dwell-time distribution, whereas the third and higher moments do not. We also discuss operational approaches and approximations to measure the flux-flux correlation function and thus the second moment of the dwell time, which is shown to be characteristically quantum, and larger than the corresponding classical moment even for freely moving particles.
We study the effect of quantum motion in a Mach-Zehnder interferometer where ultracold, two-level atoms cross a $pi/2 $-$pi $-$pi/2$ configuration of separated, laser illuminated regions. Explicit and exact expressions are obtained for transmission a
mplitudes of monochromatic, incident atomic waves using recurrence relations which take into account all possible paths: the direct ones usually considered in the simple semiclassical treatment, but including quantum motion corrections, and the paths in which the atoms are repeatedly reflected at the fields.
