Performance analysis of decoy state quantum key distribution over underwater turbulence channels

Decoy state quantum key distribution protocols have been studied for atmospheric, fiber, and satellite links; however, those results are not directly applicable to underwater environments with different channel characteristics. In this paper, we investigate the fundamental performance limits of decoy state BB84 protocol over turbulent underwater channels and provide a comprehensive performance characterization. We adopt a near field analysis to determine the average power transfer over a turbulent underwater path and use this to obtain a lower bound on the secret key rate. We quantify the performance of decoy BB84 protocol in different water types assuming various turbulence conditions. We further investigate the effect of system parameters such as transmit aperture size and detector field of view on the performance.