SKR Analysis of One- and Two-Way CV-QKD MIMO FSO Communication System

We present novel one-way and two-way continuous-variable quantum key distribution frameworks integrating multiple-input multiple-output (MIMO) and free-space optical systems to enhance secret key rates (SKRs) and extend transmission distance between the legitimate transceiver pair. Our models are subjected to an eavesdropper employing Gaussian collective attacks, and the receiver using homodyne detection for secret key reception. Novel expressions for the SKRs for both frameworks are computed, and asymptotic results demonstrate that both the SKR gains from employing MIMO and the two-way protocol are proportional to squared-root of the MIMO channels.