Research Article

Unconditional Security of Quantum Key Distribution over Arbitrarily Long Distances

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Science  26 Mar 1999:
Vol. 283, Issue 5410, pp. 2050-2056
DOI: 10.1126/science.283.5410.2050

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Quantum key distribution is widely thought to offer unconditional security in communication between two users. Unfortunately, a widely accepted proof of its security in the presence of source, device, and channel noises has been missing. This long-standing problem is solved here by showing that, given fault-tolerant quantum computers, quantum key distribution over an arbitrarily long distance of a realistic noisy channel can be made unconditionally secure. The proof is reduced from a noisy quantum scheme to a noiseless quantum scheme and then from a noiseless quantum scheme to a noiseless classical scheme, which can then be tackled by classical probability theory.

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