Design and Analysis of Octa-phase Shift Keying Based Quantum Key Distribution System
Ragini Verma, Anshul Jaiswal, Anh T. Pham · IEEE Communications Letters · 2023
This letter proposes a novel modulation signaling-based quantum key distribution (QKD) protocol that employs eight phases of the optical carrier, therefore named octa-phase shift keying QKD (8PSK-QKD). The proposed QKD protocol shares two key bits simultaneously and consequently exhibits increased spectral efficiency compared to existing modulation signaling-based QKD protocols. Different performance metrics, viz., probability of sifted keys ($P _{\text{sift}}$), quantum bit error rate, probability of sifted keys of Eve, and Eve’s error probability ($P _{\text{eve}}$), are determined using a novel analytical framework for a free-space optical channel under the combined effect of atmospheric turbulence and pointing error. To inspect the potential of the system, the 8PSK-QKD system is compared with the quadrature phase shift keying-based QKD (QPSK-QKD) and subcarrier intensity modulation binary phase shift keying-based QKD (SIM/BPSK-QKD) systems. Numerical results reveal that the 8PSK-QKD system follows the criteria of an acceptable QKD system even with transmitting two key bits at a time. Additionally, the 8PSK-QKD system outperform the SIM/BPSK-QKD and QPSK-QKD by offering better$P _{\text{sift}}$and$P _{\text{eve}}$.