We consider the influence of a resonant control field on weak localization of
light in ultracold atomic ensembles. Both steady-state and pulsed light
excitation are considered. We show that the presence of a control field
essentially changes the type of interference effects which occur under
conditions of multiple scattering. For example, for some scattering
polarization channels the presence of a control field can cause destructive
interference through which the enhancement factor, normally considered to be
greater than one, becomes less than one.Comment: Submitted to Journal of Modern Optics, Special Issue: Proceedings of
PQE 201