Mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states

A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed, named HPCS-PDS-MP-QKD protocol, where the light sources at Alice and Bob sides are changed to heralded pair-coherent sources, and devices designed to implement passive decoy states are included at the transmitter sides to generate the decoy state pulses in the decoy-state window passively. With the defined efficient events and the designed pairing strategy, the key bits and bases can be obtained by data post-processing. Numerical simulation results verify the feasibility of the proposed protocol. The results show that the proposed protocol can exceed PLOB when the pairing interval setting is greater than 10³, and the transmission distance exceeds 200 km. When the key transmission distance reaches 300 km and the maximum pairing interval is equivalent to 1, its performance is improved by nearly 1.8 times compared to the original MP-QKD protocol with a weak coherent source (WCS-MP-QKD), and by 6.8 times higher than that of WCS-MP-QKD with passive decoy states (WCS-PDS-MP-QKD). Meanwhile, the key transmission distance can reach 480 km, and surpasses the WCS-PDS-MP-QKD protocol by nearly 40 km. When the total pulse length is greater than 10¹¹, the key generation rate is almost equal to that of infinite pulses. It is a promising QKD protocol that breaks the PLOB bound without requiring phase tracking and locking, has a longer transmission distance and a higher key generation rate, and eliminates the potential of side channel attack.