Because it allows a strong, controllable, and coherent light-matter interaction, electromagnetically induced transparency (EIT) is nowadays used in a wide range of physical phenomena. However, in the D2 line of 133Cs, and in the presence of inhomogeneous broadening, the experimentally measured transparency is very weak. We thus investigate theoretically a model that takes into account the multiple excited levels of the line and identify the influence of each of them on the EIT. The study concludes that some particular velocity classes of atoms are responsible for the loss of the EIT. We then propose an original method that permits to restore the transparency by velocity distribution shaping. Finally, the expected increase of the transparency is experimentally demonstrated. Then, two EIT-based quantum memory experiments are presented. In the first one, two orthogonal quadratures of a single-sideband were stored without excess noise in a hot vapor of Cs. In the second one, the storage of a coherent state in the single photon regime in a cloud of cold atoms is obtained. In order to prepare the storage of non classical light, the lock of the homodyne measurement in a fixed quadrature of a squeezed state is realized. This experiment should lead to the demonstration of on demand entanglement of two atomic ensembles.
