Abstract: The Monte Carlo method is used to study the underwater transmission characteristics of polarized photons in four sea areas with different surface chlorophyll concentrations. First, a vertical transmission model of underwater quantum is established. Based on the model, the variations of chlorophyll concentration, absorption coefficient and scattering coefficient of light signal with seawater depth in the four sea areas are studied. In addition, analysis of the variation of polarization photon's scattering, attenuation and polarization characteristics with the transmission distance in four sea areas is carried out. The expression of calculating the number of received photons at different transmission distances is derived. The simulation results show that the absorption and scattering of optical signals in seawater channel are mainly affected by chlorophyll. With the increase of chlorophyll concentration in the surface layer of different sea areas, the scattering numbers of photons increase, whereas the farthest receiving distance decreases. The degree of polarization is also slightly reduced but basically remains unchanged. The research can shed some light on the performance analysis and the establishment of the satellite-submersible quantum communication system.

Key words: quantum communication, sea water channel, Monte Carlo method, chlorophyll concentration, degree of polarization