Applied Physics

Remember, Repeat After Me

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Science  19 Feb 2010:
Vol. 327, Issue 5968, pp. 923-925
DOI: 10.1126/science.327.5968.923-d

Quantum information processors in which information is encoded in single photons require the development of multiple components, to generate the single photons, store them, and then reliably read them from memory and pass them on. Light, however, is always on the move, usually quickly, and so solid-state quantum memories represent a crucial component, as they would allow the bits of information to be stored while other bits can be manipulated. Afzelius et al. present a solid-state quantum memory in which an absorbed photon is stored as an electronic excitation within a rare earth ion–doped crystal. The energy levels and optical transitions of the crystal can be controlled and manipulated by a series of laser pulses, so that the absorbed photon can be stored for several tens of microseconds. The process can then be reversed to retrieve the photon from the stored electronic state. Such a robust on-demand quantum memory and repeater should prove invaluable for long-distance quantum communication networks.

Phys. Rev. Lett. 104, 40503 (2010).

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