FSO-QKD protocols under free space losses and device imperfections: a comparative study

Abstract: Quantum key distribution (QKD) is a technique to establish a secret key between two parties through a quantum channel. Several QKD protocols have been proposed and implemented over optical fibers or free space links. The main challenge of operating QKD protocols over a free space link is atmospheric losses. In this paper, we have studied and compared the performance of single and entangled photon based QKD protocols by evaluating the quantum bit error rate and secure key rate for terrestrial free-space quantum communication by considering different free-space losses, such as geometrical losses, atmospheric losses as well as device imperfections.