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Equivalence between two-qubit entanglement and secure key distribution

Antonio Acin·Lluis Masanes·Nicolas Gisin
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Abstract

We study the problem of secret key distillation from bipartite states in the scenario where Alice and Bob can only perform measurements at the single-copy level and classically process the obtained outcomes. Even with these limitations, secret bits can be asymptotically distilled by the honest parties from any two-qubit entangled state, under any individual attack. Our results point out a complete equivalence between two-qubit entanglement and secure key distribution: a key can be established through a one-qubit channel if and only if it allows to distribute entanglement. These results can be generalized to higher dimension for all those states that are one-copy distillable.

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Antonio Acin, Lluis Masanes, Nicolas Gisin. 2003-09-23. Equivalence between two-qubit entanglement and secure key distribution. https://doi.org/10.1103/physrevlett.91.167901

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