Effects of detector efficiency mismatch on security of quantum cryptosystems

摘要

We suggest a new type of attack on quantum cryptosystems, exploiting differences in the detector timing. When an eavesdropper sends short pulses using the appropriate timing so that the two detectors in Bob's setup have different efficiencies, the security of quantum key distribution can be compromised. We derive security bounds as a function of the detector sensitivity mismatch for the BB84 protocol. Experimental data for two different detectors is presented, and protection measures against this attack are discussed.