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Quantum memory, entanglement and sensing with room temperature atoms

K. Jensen, W. Wasilewski, H. Krauter, T. Fernholz, B.M. Nielsen, J.M. Petersen, J.J. Renema, M.V. Balabas, M. Owari, M.B. Plenio, A. Serafini, M.M. Wolf, C.A. Muschik, J.I. Cirac, J.H. Müller, E.S. Polzik

J. Phys.: Conf. Ser. 264 012022 **, (2011)

DOI: doi:10.1088/1742-6596/264/1/012022 Pfeil

Abstract: Room temperature atomic ensembles in a spin-protected environment are useful systems both for quantum information science and metrology. Here we utilize a setup consisting of two atomic ensembles as a memory for quantum information initially encoded in the polarization state of two entangled light modes. We also use the ensembles as a radio frequency entanglement-assisted magnetometer with projection noise limited sensitivity below femtoTesla/$\sqrt{Hz}$. The performance of the quantum memory as well as the magnetometer was improved by spin-squeezed or entangled atomic states generated by quantum non demolition measurements. Finally, we present preliminary results of long lived entangled atomic states generated by dissipation. With the method presented, one should be able to generate an entangled steady state.