Abstract
A quantum memory for light is a key element for the realization of future quantum information networks1,2,3. Requirements for a good quantum memory are versatility (allowing a wide range of inputs) and preservation of quantum information in a way unattainable with any classical memory device. Here we demonstrate such a quantum memory for continuous-variable entangled states, which play a fundamental role in quantum information processing4,5,6. We store an extensive alphabet of two-mode 6.0 dB squeezed states obtained by varying the orientation of squeezing and the displacement of the states. The two components of the entangled state are stored in two room-temperature cells separated by 0.5 m, one for each mode, with a memory time of 1 ms. The true quantum character of the memory is rigorously proved by showing that the experimental memory fidelity 0.52±0.02 significantly exceeds the benchmark of 0.45 for the best possible classical memory for a range of displacements.
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Acknowledgements
This work was supported by EU projects QESSENCE, HIDEAS, CORNER, COMPAS, EMALI and COQUIT.
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Experimental group: K.J., W.W., H.K., T.F., B.M.N. and E.S.P. Calculation of the classical benchmark: M.O., M.B.P., A.S. and M.M.W.
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Jensen, K., Wasilewski, W., Krauter, H. et al. Quantum memory for entangled continuous-variable states. Nature Phys 7, 13–16 (2011). https://doi.org/10.1038/nphys1819
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DOI: https://doi.org/10.1038/nphys1819
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