Broadband Quantum Memory in Atomic Ensembles

TL;DR

This paper reviews the challenges, theoretical foundations, and current performance of broadband quantum memory in atomic ensembles, emphasizing the linewidth-bandwidth mismatch problem and various protocols to optimize efficiency and noise.

Contribution

It provides a comprehensive review of the theoretical and experimental progress in broadband atomic ensemble quantum memories, highlighting the state-of-the-art performance metrics.

Findings

Analysis of the linewidth-bandwidth mismatch problem

Comparison of different memory protocols and hardware

Current performance metrics of efficiency, lifetime, and noise

Abstract

Broadband quantum memory is critical to enabling the operation of emerging photonic quantum technology at high speeds. Here we review a central challenge to achieving broadband quantum memory in atomic ensembles -- what we call the 'linewidth-bandwidth mismatch' problem -- and the relative merits of various memory protocols and hardware used for accomplishing this task. We also review the theory underlying atomic ensemble quantum memory and its extensions to optimizing memory efficiency and characterizing memory sensitivity. Finally, we examine the state-of-the-art performance of broadband atomic ensemble quantum memories with respect to three key metrics: efficiency, memory lifetime, and noise.