Fuchs-Peres-Brandt Attack on Quantum Key Distribution

Fuchs and Peres described the most general way in which an individual attack could be mounted against single-photon, polarization-based Bennett-Brassard 1984 quantum key distribution. Eve interacts a probe photon with Alice's photon in a unitary manner, then sends Alice's photon to Bob, and performs a probability operator-valued measurement on her probe photon. Slutsky et al. demonstrated that the Fuchs-Peres construct -- with the appropriate choice of probe state, interaction, and measurement -- affords Eve the maximum amount of Rényi information about the error-free sifted bits that Bob receives for a given level of disturbance. Brandt extended the Slutsky et al. treatment by showing that the optimal probe could be realized with a single controlled-NOT (CNOT) gate. We then showed how a complete physical simulation of the Fuchs-Peres-Brandt (FPB) probe could be accomplished using single-photon two-qubit (SPTQ) quantum logic. We have implemented that experiment and are collecting data that will permit a full exploration of the power of the FPB probe.