Quantum memories are essential for large-scale quantum information networks. Along with high efficiency, storage lifetime and optical bandwidth, it is critical that the memory add negligible noise to the recalled signal. A common source of noise in optical quantum memories is spontaneous four-wave mixing. We develop and implement a technically simple scheme to suppress this noise mechanism by means of quantum interference. Using this scheme with a Raman memory in warm atomic vapour we demonstrate over an order of magnitude improvement in noise performance. Furthermore we demonstrate a method to quantify the remaining noise contributions and present a route to enable further noise suppression. Our scheme opens the way to quantum demonstrations using a broadband memory, significantly advancing the search for scalable quantum photonic networks.
@article{arxiv.1905.00042,
title = {Raman Quantum Memory with Built-In Suppression of Four-wave Mixing Noise},
author = {Sarah E. Thomas and Thomas M. Hird and Joseph H. D. Munns and Benjamin Brecht and Dylan J. Saunders and Joshua Nunn and Ian A. Walmsley and Patrick M. Ledingham},
journal= {arXiv preprint arXiv:1905.00042},
year = {2019}
}