Explicit attacks on the Bennett-Brassard 1984 protocol with partially distinguishable photons

Distinguishability of photons in non-operational degrees freedom compromises unconditional security quantum key distribution since an eavesdropper can improve attack strategies by exploiting this distinguishability. However, the optimal eavesdropping presence light source side channels are not known. Here we provide several explicit on BB84 protocol with partially distinguishable photons. In particular, consider phase-covariant cloning attack, which is absence channels, and show that there even better channels. The improved exploit a measurement channel state followed signal photon. Our results explicitly demonstrate reduction critical error rate, set upper bound practical secret rate.