Applicability of quantum key distribution technology under free-space atmospheric conditions to construct segments of modern quantum communication networks

Subject of study. This study examined the applicability of quantum key distribution (QKD) technology under free-space atmospheric conditions. Aim of study. The objective was the development of a hardware and software system for investigating the applicability of QKD technology in wireless communication systems based on commercially available modules. The system includes optical blocks for atmospheric optical communication and a training setup for studying QKD in fiber-optic communication lines. Method. The characteristics of a quantum communication channel in free-space conditions were studied through experiments. The channel was formed by the QKD units of the EMQOS 1.0 scientific and educational complex, integrated with optical blocks for atmospheric optical communication. The systems were also upgraded to minimize losses in the quantum channel. Main results. A hardware and software system was developed, within which the transmission of a quantum key through free-space atmospheric conditions over a distance of 180 m was successfully demonstrated. The quantum bit error rate did not exceed 6%. This system enabled the study of the effects of weather conditions on optical losses in the quantum communication channel and the quantum key generation rate. Practical significance. The developed hardware and software system allows the monitoring of the parameters of both classical and quantum communication channels in free space under various weather conditions. Its modular structure enables the integration of other quantum equipment for comparative testing of the performance of quantum communication systems under real atmospheric transmission conditions.