Subject of study. The effect of different quantum efficiencies of single-photon detectors in quantum key distribution (QKD) systems implementing the BB84 protocol with passive basis choice is investigated. Aim of study. The aim of this study is to determine the secret key generation rate and security of the final key in quantum cryptography systems as functions of detector efficiency mismatch. Additionally, an analytical equation is derived for estimating the secret key generation rate in quantum communication systems with passive basis choice while accounting for different detector efficiencies. Method. The secret key is calculated by dividing the received measurement data according to the measurement bases, followed by performing separate post-processing for each dataset, and finally summing the resulting estimates of the secret key. Main results. An analytical method for estimating the secret key generation rate in systems with passive basis choice and mismatched detector efficiencies is developed. A satellite-to-ground quantum communication channel is modeled using the parameters of the Zvenigorod Observatory in Russia. The proposed theory for accounting for the detector efficiency mismatch is applied to a model of a satellite QKD system, and the determined length of the secret key generated during a single communication session with the satellite is found to be 300 kbit. Practical significance. The obtained results account for the effect of detector efficiency mismatch when estimating the length of the secret key in QKD systems, thereby increasing their reliability in practical implementations.
Ivchenko et al. (Tue,) studied this question.