Mode-pairing quantum key distribution with multi-step advantage distillation

Abstract The advantage distillation (AD) technology has been proven to effectively improve the secret key rate and the communication distance of quantum key distribution (QKD). The mode-pairing quantum key distribution (MP-QKD) protocol can overcome a fundamental physical limit, known as Pirandola-Laurenza-Ottaviani-Banchi bound, without requiring global phase-locking. In this work, we propose a method based on multi-step AD to further enhance the performance of MP-QKD. The simulation results show that, compared to one-step AD, multi-step AD achieves better performance in long-distance scenarios and can tolerate a higher quantum bit error rates. Specifically, when the difference between the communication distances from Alice and Bob to Charlie of 25 km, 50 km and 75 km, respectively, and the corresponding transmission distances exceeds 523 km, 512 km, and 496 km, respectively, the secret key rate achieved by multi-step AD surpasses that of one-step AD. Our findings indicate that the proposed method can effectively promote the application of MP-QKD in scenarios with high loss and high error rate.