Terahertz continuous-variable quantum key distribution in atmospheric environment: theory and performance analysis

Quantum Key Distribution (QKD) technology, based on the principles of quantum mechanics, provides theoretically unconditional security for information exchange, enabling effective detection and resistance against potential eavesdropping. QKD is categorized into discrete variable QKD (DVQKD) and continuous variable QKD (CVQKD), with this study focusing on theoretical analysis within the terahertz (THz) spectrum. By comparing the performance of the direct reconciliation homodyne detection protocol with the reverse reconciliation homodyne detection protocol, the secure key rate and transmission distance of the CVQKD system in the 0.1-1THz frequency range are investigated under both atmospheric absorption loss alone and the combined effects of atmospheric absorption loss and free-space path loss. The investigation further underscores the beneficial effects of increased antenna gain in mitigating losses, underscoring the critical role of judicious antenna design in maximizing the performance of QKD systems Furthermore, it reviews the latest international advancements in high-gain antennas within the 0.1-1THz band.