Long-lived spin state of an atomic gas-a storage medium for a quantum state of light

Summary form only given. The spin polarized ground state of a cesium gas in a paraffin coated glass cell at room temperature has been recently used for generation of a long lived entangled state of atoms. In this paper we report on the first results towards using this medium as a quantum memory for polarization states of a light beam. The possibility of a reversible transfer of polarization states between light and atoms via interspecies teleportation protocols has been previously proposed. A narrowband tunable source of entangled light needed for such a transfer has been constructed before. We demonstrate that our set-up allows detection of the quantum state of light propagating through an atomic sample by means of observing the state of the long lived collective spin of the sample. For this purpose a polarization squeezed optical probe is prepared by mixing orthogonally polarized squeezed vacuum and coherent light with a variable phase on a polarizing beamsplitter.