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Robustness of the BB84 quantum key distribution protocol against general coherent attacks

Georgios M. Nikolopoulos·Gernot Alber
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Abstract

It is demonstrated that for the entanglement-based version of the Bennett-Brassard (BB84) quantum key distribution protocol, Alice and Bob share provable entanglement if and only if the estimated qubit error rate is below 25% or above 75%. In view of the intimate relation between entanglement and security, this result sheds also new light on the unconditional security of the BB84 protocol in its original prepare-and-measure form. In particular, it indicates that for small qubit error rates 25% is the ultimate upper security bound for any prepare-and-measure BB84-type QKD protocol. On the contrary, for qubit error rates between 25% and 75% we demonstrate that the correlations shared between Alice and Bob can always be explained by separable states and thus, no secret key can be distilled in this regime.

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Georgios M. Nikolopoulos, Gernot Alber. 2005-01-11. Robustness of the BB84 quantum key distribution protocol against general coherent attacks. https://doi.org/10.1140/epjd%2Fe2005-00314-3

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