We review a series of quantum memory protocols designed to store the quantum information carried by light into atomic ensembles. In particular, we show how a simple semiclassical formalism allows to gain insight into various memory protocols and to highlight strong analogies between them. These analogies naturally lead to a classification of light storage protocols into two categories, namely photon echo and slow-light memories. We focus on the storage and retrieval dynamics as a key step to map the optical information into the atomic excitation. We finally review various criteria adapted for both continuous variables and photon-counting measurement techniques to certify the quantum nature of these memory protocols.
@article{arxiv.1801.10023,
title = {Quantum optical memory protocols in atomic ensembles},
author = {Thierry Chanelière and Gabriel Hétet and Nicolas Sangouard},
journal= {arXiv preprint arXiv:1801.10023},
year = {2019}
}