  Theoretical prediction of antilocalization of light in ultracold atomic gas
samples, in the weak localization regime, is reported. Calculations and
Monte-Carlo simulations show that, for selected spectral ranges in the vicinity
of atomic 85Rb hyperfine transitions, quantum coherence in optical transitions
through nondegenerate hyperfine levels in multiple light scattering generates
destructive interference in otherwise reciprocal scattering paths. This effect
leads to enhancement factors less than unity in a coherent backscattering
geometry, and suggests the possibility of enhanced diffusion of light in
ultracold atomic vapors.
