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Long-distance quantum communication with atomic ensembles and linear optics


Quantum communication holds promise for absolutely secure transmission of secret messages and the faithful transfer of unknown quantum states. Photonic channels appear to be very attractive for the physical implementation of quantum communication. However, owing to losses and decoherence in the channel, the communication fidelity decreases exponentially with the channel length. Here we describe a scheme that allows the implementation of robust quantum communication over long lossy channels. The scheme involves laser manipulation of atomic ensembles, beam splitters, and single-photon detectors with moderate efficiencies, and is therefore compatible with current experimental technology. We show that the communication efficiency scales polynomially with the channel length, and hence the scheme should be operable over very long distances.

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Figure 1: Set-up for entanglement generation.
Figure 2: Set-up for entanglement connection.
Figure 3: Set-up for entanglement-based communication schemes.

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This work was supported by the Austrian Science Foundation, the Europe Union project EQUIP, the ESF, the European TMR network Quantum Information, and the NSF through a grant to the ITAMP and ITR program. L.-M.D. was also supported by the Chinese Science Foundation.

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Correspondence to J. I. Cirac.

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Duan, LM., Lukin, M., Cirac, J. et al. Long-distance quantum communication with atomic ensembles and linear optics. Nature 414, 413–418 (2001).

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