Multiple Pulses Phase-matching Quantum Key Distribution

TL;DR

This paper introduces a multiple pulses phase-matching quantum key distribution protocol (MPPM-QKD) that surpasses existing rate limits and error tolerances, enabling secure long-distance communication with higher efficiency.

Contribution

The proposed MPPM-QKD protocol exceeds the rate-loss limit and offers higher error tolerance compared to existing protocols, especially for long-distance quantum key distribution.

Findings

Secret key rate beats rate-loss limit beyond 250 km

Higher error tolerance of approximately 24% at 50 km with L=128

Outperforms round-robin DPS, MDI-QKD, and phase-matching QKD in key rate and distance

Abstract

We propose a multiple pulses phase-matching quantum key distribution protocol (MPPM-QKD) to exceed the linear key rate bound and to achieve higher error tolerance. In our protocol, Alice and Bob generate at first their own train pulses (each train should contain L pulses) as well as random bit sequences, and also encode each pulse of their trains with a randomized phase and a modulation phase. As the next step, both encoded trains are simultaneously sent to Charlie, who performs an interference detection and may be also an eavesdropper. After a successful detection is announced by Charlie, Alice and Bob open the randomized phase of each pulse and keep only communications when the summation of the difference randomized phases at two success detection's time-stamps for Alice and Bob are equal to 0 or pi. Thereafter, Alice and Bob compute the sifted key with the time-stamps. The above procedure is repeated until both Alice and Bob achieve sufficiently long sifted keys. We can also show that the secret key rate of the proposed QKD protocol can beat the rate-loss limit of so far known QKD protocols when the transmission distance is greater than 250 km. Moreover, the proposed protocol has a higher error tolerance, approximately 24%, when the transmission distance is 50 km and L = 128. The secret key rate and the transmission distance of our protocol are superior to that of the round-robin differential-phase-shift quantum key distribution protocol [6], and also of the measurement-device-independent quantum key distribution protocol [4], and the secret key rate performance is better in both cases than that of phase-matching quantum key distribution when bit train length is greater than 32.