Phase-Matching Quantum Key Distribution with Discrete Phase Randomization

Abstract

The twin-field quantum key distribution (TF-QKD) protocol and its variations have been proposed to overcome the linear Pirandola–Laurenza–Ottaviani–Banchi (PLOB) bound. One variation called phase-matching QKD (PM-QKD) protocol employs discrete phase randomization and the phase post-compensation technique to improve the key rate quadratically. However, the discrete phase randomization opens a loophole to threaten the actual security. In this paper, we first introduce the unambiguous state discrimination (USD) measurement and the photon-number-splitting (PNS) attack against PM-QKD with imperfect phase randomization. Then, we prove the rigorous security of decoy state PM-QKD with discrete phase randomization. Simulation results show that, considering the intrinsic bit error rate and sifting factor, there is an optimal discrete phase randomization value to guarantee security and performance. Furthermore, as the number of discrete phase randomization increases, the key rate of adopting vacuum and one decoy state approaches infinite decoy states, the key rate between discrete phase randomization and continuous phase randomization is almost the same.

Phase-matching quantum key distribution with imperfect sources

“…However, when we consider the actual security of the PMDs, THAs, and CCs, it is realized that the fundamental implicit assumption of decoy states analysis that the yield is independent of intensity setting is invalid. [23,27] Therefore, considering the properties of trace distance, we have…”

“…In recent years, QKD has made tremendous progress, which includes the realization of longdistance fiber communication systems [1][2][3][4][5][6][7][8][9][10][11] and the deployment of QKD networks. [12][13][14][15] Although the theoretical assumptions of QKD are impeccable, the actual devices have potential security loopholes, [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] which seriously threaten the security of QKD.…”

“…The SPFs caused by randomization of discrete are also studied in Refs. [22,23]. For the side channels of MDs, which exist in various degrees of freedom, the polarization MDs (PMDs) are common loopholes in phase coding, and the security may be severely affected by the PMDs.…”

Physical-Layer Security, Quantum Key Distribution, and Post-Quantum Cryptography

“…In the seventh article [ 18 ], authors study the phase-matching QKD (PM-QKD) protocol, employing discrete-phase randomization and the post-compensation phase to quadratically improve the SKR. Unfortunately, according to the authors, the discrete-phase randomization opens a security loophole.…”