Atomic-ensemble-based quantum memory for sideband modulations

TL;DR

This paper demonstrates a quantum memory using atomic ensembles that can store and retrieve sideband modulations of light with low noise, analyzing conditions for simultaneous storage of non-commuting variables.

Contribution

It introduces a method for storing and retrieving sideband modulations in atomic ensembles, comparing single-sideband and dual-sideband storage within the same transparency window.

Findings

Low excess noise during storage and retrieval.

Successful simultaneous storage of non-commuting variables.

Quantitative evaluation of quantum performance using T-V criterion.

Abstract

Interaction of a control and a signal field with an ensemble of three-level atoms allows direct mapping of the quantum state of the signal field into long lived coherences of an atomic ground state. For a vapor of cesium atoms, using Electromagnetically Induced Transparency (EIT) and Zeeman coherences, we compare the case where a tunable single-sideband is stored independently of the other one to the case where the two symmetrical sidebands are stored using the same transparency window. We study the conditions in which simultaneous storage of two non-commuting variables carried by light and subsequent read-out is possible. We show that excess noise associated with spontaneous emission and spin relaxation is small, and we evaluate the quantum performance of our memory by measuring the signal transfer coefficient T and the conditional variance V and using the T-V criterion as a state independent benchmark.