We show that coherent multiple light scattering, or diffuse light propagation, in a disordered atomic medium, prepared at ultra-low temperatures, can be be effectively delayed in the presence of a strong control field initiating a stimulated Raman pr
ocess. On a relatively short time scale, when the atomic system can preserve its configuration and effects of atomic motion can be ignored, the scattered signal pulse, diffusely propagating via multiple coherent scattering through the medium, can be stored in the spin subsystem through its stimulated Raman-type conversion into spin coherence. We demonstrate how this mechanism, potentially interesting for developing quantum memories, would work for the example of a coherent light pulse propagating through an alkali-metal atomic vapor under typical conditions attainable in experiments with ultracold atoms.
We consider the motion of an overdamped particle in a periodic potential lacking spatial symmetry under the influence of symmetric Levy noise, being a minimal setup for a ``Levy ratchet. Due to the non-thermal character of the Levy noise, the particl
e exhibits a motion with a preferred direction even in the absence of whatever additional time-dependent forces. The examination of the Levy ratchet has to be based on the characteristics of directionality which are different from typically used measures like mean current and the dispersion of particles positions, since these get inappropriate when the moments of the noise diverge. To overcome this problem, we discuss robust measures of directionality of transport like the position of the median of the particles displacements distribution characterizing the group velocity, and the interquantile distance giving the measure of the distributions width. Moreover, we analyze the behavior of splitting probabilities for leaving an interval of a given length unveiling qualitative differences between the noises with Levy indices below and above unity. Finally, we inspect the problem of the first escape from an interval of given length revealing independence of exit times on the structure of the potential.
