An important challenge for quantum information networks is the development of efficient quantum memories and sources of single-photons. A promising category of such devices is based on ensembles of neutral atoms. The motivation comes from the fact that collective effects related to large number of atoms make it much easier in principle to achieve a strong and controllable coupling between the medium and the light. The present project aims at performing such experiments based on an ensemble of cold atoms trapped in the vicinity of a nanofiber, which will enable to obtain a larger optical thickness, a better coupling between collective excitations and light modes and thus a larger efficiency than previous ensemble-based implementations.