Performance of Scarani-Acin-Ribordy-Gisin protocol in quantum key distribution

The Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocol was proposed by V. Scarani et al. In this paper, the performance of SARG04 protocols utilizing weak coherent state (WCS) and heralded single photon source (HSPS) are investigated, and the influence of decoy-state idea on SARG04 protocol is analyzed. Furthermore, the choice of optimal signal intensity for SARG04 protocol is discussed and the condition that the optimal signal intensity satisfies is obtained. The simulation and analysis results show that SARG04 protocol with WCS has the best key generation rate and transmission distance (88 km) comparing with SARG04 protocol with HSPS, BB84 protocol with WCS or HSPS. The decoy state method can substantially prolong the secure distance of SARG04 protocol to 165 km with WCS and 173 km with HSPS, and the performance of decoy-state SARG04 protocol is better than that of decoy-state BB84 protocol. The decoy state method weakens the dependence of the optimal signal intensity on the overall transmission probability.