Retrieval of phase memory in two independent atomic ensembles by Raman process

TL;DR

This paper demonstrates phase memory retrieval in atomic ensembles via Raman processes, revealing phase correlations crucial for advancing macroscopic entanglement between light and atoms.

Contribution

It introduces a method to read out atomic phase memory through a second Raman process, enabling phase correlation measurement between light and atomic states.

Findings

Phase of atomic ensembles can be read out via Raman process.

Atomic and light phases are anti-correlated and can be retrieved.

Results support potential for macroscopic entanglement.

Abstract

In spontaneous Raman process in atomic cell at high gain, both the Stokes field and the accompanying collective atomic excitation (atomic spin wave) are coherent. We find that, due to the spontaneous nature of the process, the phases of the Stokes field and the atomic spin wave change randomly from one realization to another but are anti-correlated. The phases of the atomic ensembles are read out via another Raman process at a later time, thus realizing phase memory in atoms. The observation of phase correlation between the Stokes field and the collective atomic excitations is an important step towards macroscopic EPR-type entanglement of continuous variables between light and atoms.