Abstract: Quantum communication has attracted significant attention because of its high confidentiality. Nevertheless, when optical quantum signals are transmitted from the ocean surface to the underwater, they inevitably encounter attenuation due to interactions with water molecules, bubble particles, and chlorophyll particles in the seawater, which restricts their transmission range and quality. To investigate the impact of the marine surface system on the performance of underwater quantum communication channels, a model is first established to elucidate the extinction effects of the marine surface system in this work. The model facilitates the examination of how varying parameters of the marine surface system influence the transmission efficiency and link attenuation in underwater quantum communications. Furthermore, with a focus on amplitude damping channels, the study investigates the relationship between incident light wavelength, transmission depth and channel capacity, channel survival function in the marine surface system environment. In addition, the effects of the marine surface system on bit error rate and coding rate during the quantum key distribution process are also examined. The findings reveal that when the incident wavelength is in the range of 400–800 nm, as the incident light wavelength decreases and the transmission depth increases, the link attenuation and system bit error rate of underwater quantum channels increase, while the channel transmittance, channel capacity, channel survival function, and system coding rate progressively decline.

Key words: quantum communication, marine surface system, channel capacity, bit error rate, coding rate