Quantum optical memory protocols in atomic ensembles

TL;DR

This paper reviews quantum memory protocols in atomic ensembles, classifying them into photon echo and slow-light types, and discusses their dynamics and criteria for quantum certification.

Contribution

It introduces a unified semiclassical framework to analyze and classify quantum memory protocols in atomic ensembles, highlighting their similarities and differences.

Findings

Classification of memory protocols into two main categories

Insights into storage and retrieval dynamics

Criteria for quantum nature certification

Abstract

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.