We experimentally establish a non-classical correlation between a single Stokes photon and the collective spin excited state of a cold atomic ensemble by using a spontaneous Raman scattering process. The correlation between them can be proved by transferring the spin excited state of the atomic ensemble into an anti-Stokes photon and checking the Cauchy-Schwarz inequality between the Stokes and the anti-Stokes photons. The non-classical correlation can be kept for at least 300 ns.
© 2009 Chinese Optics Letters
Xiaosong Lu, Qunfeng Chen, Baosen Shi, and Guangcan Guo, "Non-classical correlation between a single photon and the collective spin excited state of a cold atomic ensemble," Chin. Opt. Lett. 7, 1048-1050 (2009)