Limitation of decoy-state Scarani-Acin-Ribordy-Gisin quantum-key- distribution protocols with a heralded single-photon source

For the Bennett-Brassard 1984 (BB84) quantum key distribution, longer distance and higher key generating rate is shown with a heralded single-photon source (HSPS). In this paper, the performance of the Scarani-Acin-Ribordy-Gisim (SARG) protocol utilizing the HSPS sources is considered and the numerical simulation turns out that still a significant improvement in secret key generating rate can also be observed. It is shown that the security distance for HSPS+SARG is 120 km. However, compared with the HSPS+BB84 protocols, the HSPS+SARG protocol has a lower secret key rate and a shorter distance. Thus we show the HSPS+BB84 implementation is a preferable protocol for long distance transmittance.