Practical Nonorthogonal Decoy State Quantum Key Distribution with a Heralded Single Photon Source

For the Bennett-Brassard 1984 (BB84) quantum key distribution, longer distance and higher key generation rate is shown with a heralded single photon source (HSPS). In this paper, the nonorthogonal encoding protocol SARG04 based on one vacuum and two weak decoy states with HSPS is presented. According to the public announcement of Alice´s detection events, the overall gain of Bob´s detector and quantum bit error rate (QBER) can be divided into two groups, triggered components and nontriggered components. We present a new protocol that use both triggered and nontriggered components to estimate the fraction and QBER of single-photon and two-photon pulses, and then deduce the final secure key generation rate. The final key generation rate over transmission distance is simulated, which shows that we can obtain a higher key rate than that of the existing methods.