Reliability improvement of satellite-based quantum key distribution systems using retransmission scheme

This paper theoretically studies the design and performance analysis of the reliable satellite-based quantum key distribution (QKD) over free-space optics channel. The proposed QKD system is based on the optical quadrature phase-shift keying (QPSK) modulation and the dual-threshold/heterodyne detection (DT/HD) receiver that helps to reduce quantum bit error rate (QBER) and improve the receiver sensitivity. In addition, a key retransmission scheme is also designed to enhance the reliability of the proposed QKD system. Performance of the key transmission is analyzed in terms of QBER and the probability of sifted key, taking into account the impacts of free-space path loss, atmospheric attenuation, beam spreading loss, atmospheric turbulence, and receiver noise. In addition, we newly develop an analytical framework by using the 3-D Markov chain model that allows us to investigate the key loss rate (KLR) performance at the link layer. Numerical results quantitatively show that our proposed satellite-based QKD system can offer significant performance improvement over the conventional ones.