Experimental simulation of an underwater QKD system in a real scenario

In this work, we implement a proof-of-concept underwater free-space quantum key distribution (QKD) system and analyze its performance in a controlled laboratory test environment. We implement a BB84 protocol with time-bin encoding operating at 520 nm. The quantum channel was composed of a five-meter-long tank equipped with the possibility of actively controlling the water turbulence. Finally, we measure the quantum bit error rate (QBER) in the various scenarios and we report the results together with those relating to the parameters of the considered channel.