Scientific Calendar Event

The ability to distribute and store quantum information would provide the potential for revolutionary technological advances from completely secure communication to quantum computing.  Decoherence and propagation losses, however, severely limit our ability to implement these schemes. Quantum memories cannot be continuously read and refreshed as classical memories can since any measurement will alter the underlying state.  The only option remaining is to isolate a memory from any external influences.
We report recent implementations long-lived memories using collective excitations in atomic ensembles. Scattering of a light field from an ensemble results in the emission of a signal photon and an imprinted atomic spin wave. By understanding the primary sources of the coherence, magnetic field and atomic motion, we show how one can combat their deleterious effects.  We present an analysis of the dynamics of retrieval of information from our memories and show how it was exploited to produce memory times in excess of 6 milliseconds.  We also demonstrate how one can use controlled interactions with magnetic fields to execute qubit rotations during storage. The variation of retrieval dynamics with storage time can also be used as a measure of initial populations of the atomic states.
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