Abstract
The quantum circuit and design are presented for an optimized entangling probe attacking the BB84 Protocol of quantum key distribution (QKD) and yielding maximum information to the probe. 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 (POVM), then the measurement results are unambiguous, at least some of the time. It follows that the BB84 (Bennett–Brassard 1984) protocol of quantum key distribution has a vulnerability similar to the well-known vulnerability of the B92 (Bennett 1992) protocol
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Pacs: 03.67.Dd, 03.67.Hk, 03.65.Ta
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Brandt, H.E. Unambiguous State Discrimination in Quantum Key Distribution. Quantum Inf Process 4, 387–398 (2005). https://doi.org/10.1007/s11128-005-0003-0
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DOI: https://doi.org/10.1007/s11128-005-0003-0