Security of quantum key distribution with detection-efficiency mismatch in the single-photon case: Tight bounds
Published 2018-10-10Version 1
One of the practical challenges in practical quantum key distribution is dealing with the efficiency mismatch between different threshold detectors. There are known bounds for the secret key rate for the BB84 protocol with the detection efficiency mismatch provided that the eavesdropper sends exactly one photon to the receiver. Here we improve these bounds and give a tight bound for the secret key rate with a constant detection efficiency mismatch provided that the eavesdropper cannot send more than one photon to the receiver. In particular, the last condition means that the zero-photon case on the receiver's side, which is intricate in the case of detection-efficiency mismatch, is explicitly included in the analysis.