Realistic and general model for quantum key distribution with entangled-photon sources

Entanglement-based quantum key distribution (EB-QKD) has several advantages over prepare-and-measure protocols, such as eliminating the need for decoy states and active modulators. At present, entanglement sources based on the spontaneous parametric down-conversion process have been widely used in EB-QKD experiments. Most of the existing models regard the photon-number distribution of pulse-pumped entanglement sources as thermal. However, doing so ignores any effects of spectral modes, which will lead to the overestimation of the secure key rate. In this paper, we analyze the correlation between the photon-number distribution and the joint spectral distribution and rewrite the quantum state of the photon pairs. Then we apply the results to EB-QKD and present a general model which can be used to calculate the secure key rate not only for any pulse-pumped systems but even for cw-pumped systems.

Automated summary

This paper analyzes the correlation between the photon-number distribution and the joint spectral distribution in entanglement-based quantum key distribution (EB-QKD) and presents a general model that can be used to calculate the secure key rate for both pulse-pumped and continuous-wave (cw) pumped systems. The existing models, which consider the photon-number distribution of pulse-pumped entanglement sources as thermal, lead to an overestimation of the secure key rate due to the neglect of spectral modes.