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Conclusive Entangling Probe

Howard E. Brandt
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Abstract

A design is given for an optimized entangling probe attacking the BB84 (Bennett-Brassard 1984) protocol of quantum key distribution and yielding maximum information to the probe for a full range of induced error rates. Probe photon polarization states become optimally entangled with the signal states on their way between the legitimate transmitter and receiver. Although standard von-Neumann projective measurements of the probe yield maximum information on the pre-privacy amplified key, if instead the probe measurements are performed with a certain positive operator valued measure, then the measurement results are conclusive, at least some of the time, for a full range of inconclusive rates.

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Howard E. Brandt. 2005-09-13. Conclusive Entangling Probe. https://arxiv.org/abs/quant-ph/0509088

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