The phase matching quantum key distribution protocol with 3-state systems

Quantum key distribution allows two remote parties to generate a theoretically secure key. However, its application still faces a great challenge, that is, the fundamental linear secret key-rate constraint. Recently, several QKD schemes have been presented to obtain a secret key rate which is higher than that of the previous schemes. Based on QKD scheme, a phase-matching quantum key distribution protocol with 3-state system is proposed for the first time in this paper. Here, each successful detection is responded in three different ways, and the two parties obtain the key through "flip and flip," so this greatly improves the success rate of the phase-matching and makes the final key rate higher than that of the previous scheme. The simulation results show that the proposed protocol breaks the limit of linear key generation rate in a shorter distance, and the longest practical transmission distance is about 470 km.