Monte-Carlo-based dynamic air–water cross-media channel for continuous-variable quantum key distribution

Abstract

Cross-media and confidentiality are key features of next-generation optical communications. Quantum communication is regarded as a promising new form of secure communication. However, the cross-media transmission of quantum pulses tends to suffer from severe attenuation, which inevitably degrades the security of the whole system. In this paper, we consider the configuration of the continuous-variable quantum key distribution through an air–water cross-media channel that involves the lower-atmospheric channel, the underwater channel, and the air–water interface. We consider the effect of air bubbles in seawater, and the effect of the dynamic air–water interface as well. In particular, dynamic characteristics of light extinction and fluctuations caused by seawater and bubbles have been demonstrated with Monte Carlo (MC) simulations. Based on this MC-based model, we demonstrate the communication viability, and simulation results show that in clear seawater conditions with a wind speed of 5 m/s and a zenith angle of 15°, the receiver is able to achieve an effective secret key rate (10−4 bits/pulse) even at 9.71 m depth. Smaller zenith angles and lower wind speeds contribute to an increase in the interface secret key rate.