Light storage for 150 milliseconds at room temperature. (arXiv:1710.06844v1 [quant-ph])

Light storage is the controlled and reversible mapping of light fields onto
long-lived states of matter [1], forming the basis for quantum memories in
optical quantum networks [2-6]. Prominent storage media are warm alkali gases
due to their strong optical coupling and long-lived spin states [7-8]. In a
dense gas, the random atomic collisions dominate the lifetime of the spin
coherence, limiting the storage time to a few milliseconds [9-10]. Here we
present and experimentally demonstrate a storage scheme that is insensitive to
spin-exchange collisions, thus enabling long storage times at high atomic
densities. This unique property is achieved by mapping the light field onto
spin orientation, rather than onto higher spin moments. We report on a record
storage lifetime for a warm system of 150 milliseconds (1/e) in cesium vapor.
Furthermore, our scheme lays the foundations for hour-long quantum memories
using rare-gas nuclear spins.

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