Storage and Manipulation of Light Using a Raman Gradient Echo Process

TL;DR

This paper reviews the Lambda-GEM scheme for optical quantum memory, highlighting its ability to store, re-sequence, and retrieve light pulses using atomic ensembles, and discusses mitigating effects like four-wave mixing.

Contribution

It provides a comprehensive review of the Lambda-GEM method, including experimental insights on mitigating parasitic effects and demonstrating pulse preservation and backward retrieval.

Findings

Lambda-GEM can store and re-sequence multiple light pulses.

Mitigation of parasitic four-wave mixing improves memory performance.

Successful demonstration of pulse shape preservation and backward retrieval.

Abstract

The Gradient Echo Memory (GEM) scheme has potential to be a suitable protocol for storage and retrieval of optical quantum information. In this paper, we review the properties of the $\Lambda$-GEM method that stores information in the ground states of three-level atomic ensembles via Raman coupling. The scheme is versatile in that it can store and re-sequence multiple pulses of light. To date, this scheme has been implemented using warm rubidium gas cells. There are different phenomena that can influence the performance of these atomic systems. We investigate the impact of atomic motion and four-wave mixing and present experiments that show how parasitic four-wave mixing can be mitigated. We also use the memory to demonstrate preservation of pulse shape and the backward retrieval of pulses.