title: Observation of coherence between two independent atomic ensembles by Raman scattering.
abstract: By using spontaneous Raman processes in the high-gain regime, we create instantaneous coherence between two independent atomic ensembles. The coherence is confirmed by the observation of temporal beating between the two subsequent readout fields converted from the atomic excitations through another enhanced Raman process. The beat frequency is found to be a result of an AC Stark frequency shift effect. We find that, due to the spontaneous nature of the process, the phases of the two ensembles change from one realization to another even though there is good coherence for a single realization.
authors.affiliation: Quantum Institute for Light and Atoms, Department of Physics, East China Normal University, Shanghai 200062, China.
authors.forename: Li-Qing
authors.initials: LQ
authors.lastname: Chen
authors.forename: Guo-Wan
authors.initials: GW
authors.lastname: Zhang
authors.forename: Cheng-ling
authors.initials: CL
authors.lastname: Bian
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Ou
authors.forename: Weiping
authors.initials: W
authors.lastname: Zhang