Phase-matching quantum key distribution with the single-photon-added coherent source

Abstract

Increasing the bit rate and transmission distance of quantum key distribution (QKD) without quantum repeaters is a formidable challenge, which is limited by the secret-key capacity (SKC). Fortunately, phase-matching QKD (PM-QKD) can overcome this limitation by matching the phase of two coherent states and encoding the key information into the common phase. But the probability of the weak coherent source (WCS) sending a single photon is small, so studying the QKD of different signal sources is one of the effective ways to improve the performance of the QKD protocol. The single-photon-added coherent state (SPACS) has a high probability of sending single photons and is closer to an ideal single-photon source than WCS. We have done simulations combining the advantages of the source with the advantages of PM-QKD. Numerical simulations show that the SPACS-PM-QKD protocol also has the ability to break the SKC, and using the SPACS is better in terms of communication distance and key rate compared to WCS.