Raman scheme for adjustable bandwidth quantum memory

TL;DR

This paper introduces a Raman-based quantum memory scheme that uses atomic vapor and Doppler effects to store and retrieve light signals with adjustable bandwidth, achieving high efficiency.

Contribution

It presents a novel Raman memory protocol that allows bandwidth tuning via beam angles and predicts near-perfect efficiency at high optical depths.

Findings

Memory bandwidth is adjustable by changing beam angles.

Recovery efficiency approaches 100% with large optical depth.

The protocol enables distortion-free backward retrieval.

Abstract

We propose a scenario of quantum memory for light based on Raman scattering. The storage medium is a vapor and the different spectral components of the incoming signal are stored in different atomic velocity classes. One uses appropriate pulses to reverse the resulting Doppler phase shift and to regenerate the signal, without distortion, in the backward direction. The different stages of the protocol are detailed and the recovery efficiency is calculated in the semi-classical picture. Since the memory bandwidth is determined by the Raman transition Doppler width, it can be adjusted by changing the angle of the signal and control beams. The optical depth also depends on the beam angle. As a consequence the available optical depth can be optimized, depending on the needed bandwidth. The predicted recovery efficiency is close to 100% for large optical depth.