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

¹ Quantum Institute for Light and Atoms, Department of Physics, East China Normal University Shanghai 200062, PRC
² Department of Physics, Indiana University-Purdue University Indianapolis - 402 N. Blackford Street, Indianapolis, IN 46202, USA
³ State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University Shanghai 200062, PRC

^a zou@iupui.edu
^b wpzhang@phy.ecnu.edu.cn

Received: 15 September 2011
Accepted: 13 December 2011

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.