Practical non-orthogonal decoy state quantum key distribution with heralded single photon source

Recently the performance of the quantum key distribution (QKD) issubstantially improved by the decoy state method and thenon-orthogonal encoding protocol, separately. In this paper, apractical non-orthogonal decoy state protocol with a heralded singlephoton source (HSPS) for QKD is presented. The protocol is based on4 states with different intensities, i.e. one signal state and threedecoy states. The signal state is for generating keys; the decoystates are for detecting the eavesdropping and estimating thefraction of single-photon and two-photon pulses. We have discussedthree cases of this protocol, i.e. the general case, the optimalcase and the special case. Moreover, the final key rate overtransmission distance is simulated. For the low dark count of theHSPS and the utilization of the two-photon pulses, our protocol hasa higher key rate and a longer transmission distance than any otherdecoy state protocol.