Analysis of atmospheric effects on satellite-based quantum communication: a comparative study

TLDR: In SARG04 QKD protocol with two decoy states, the optimum signal-state mean photon number is independent of the link distance and is valid for the attacks considered here, highlighting its use in a realistic scenario of satellite quantum communication.

Abstract: Quantum key distribution (QKD) is a key exchange protocol which is implemented over free space optical links or optical fiber cable. When direct communication is not possible, QKD is performed over fiber cables, but the imperfections in detectors used at the receiver side and also the material properties of fiber cables limit the long-distance communication. Free space-based QKD is free from such limitations and can pave the way for satellite-based quantum communication to set up a global network for sharing secret messages. To implement free space optical links, it is essential to study the effect of atmospheric turbulence. Here, an analysis is made for satellite-based quantum communication using QKD protocols. We assume two specific attacks, namely PNS (photon number splitting) and IRUD (intercept-resend with unambiguous discrimination), which could be main threats for future QKD-based satellite applications. The key generation rates and the error rates of the considered QKD protocols are presented. Other parameters such as optimum signal and decoy states mean photon numbers are calculated for each protocol and distance. Further, in SARG04 QKD protocol with two decoy states, the optimum signal-state mean photon number is independent of the link distance and is valid for the attacks considered here. This is significant, highlighting its use in a realistic scenario of satellite quantum communication.