Twin-field quantum key distribution with heralded single photon source

The recently proposed twin-field quantum key distribution (TF-QKD) effectively overcomes the key capacity limitation without quantum relay and achieves long-distance quantum key distribution. In this paper, based on the TF-QKD protocol by Lucamarini et al. [M. Lucamarini, Z.L. Yuan, J.F. Dynes, A.J. Shields, Nature 557, 400 (2018)], we propose a scheme where the weak coherent state (WCS) is replaced by a heralded single photon source (HSPS), and compare their performance by calculating the key rate. The numerical simulation results show that TF-QKD using HSPS can still break through the rate-distance limitation. Specifically, compared with the WCS TF-QKD protocol, the HSPS TF-QKD protocol has a lower secret key rate but a greater distance. Thus we show the TF-QKD with HSPS is a more preferable protocol for long distance transmittance.