Coherent backscattering of light by cold atoms

Summary form only given. A wave propagating in a strongly scattering medium experiences many scattering events which rapidly erase the memory of its initial direction on a typical scale length known as the transport mean free path. It is now known that interference can profoundly alter the wave transport, a spectacular manifestation being weak and strong localisation of waves. We shall briefly review the basics of coherent backscattering (CBS) and the results obtained with classical scatterers. We shall then describe our experiment using cold atoms and discuss the experimental data. The non trivial role of the atomic quantum internal structure in the enhancement reduction will be singled out in a simple situation and results of analytical calculations will be presented.