HyeonSeok Jung

Quantum Key Distribution (QKD) has been actively studied due to its unconditional security against eavesdropping, especially in the era of quantum computing. Among various QKD implementations, free-space QKD—which transmits and receives single photons through free-space channels—has gained significant attention due to its lower signal attenuation over long distances and its potential for establishing global quantum networks without the need for fiber-optic infrastructure. Recently, it has also emerged as a promising solution for secure communications on mobile platforms such as drones and autonomous vehicles. To integrate QKD systems into compact mobile platforms, it is essential to achieve system miniaturization and weight reduction, while also maintaining stable optical link in environments with motion and vibration. One effective approach is the use of gimbal-based beam tracking systems, as gimbals are well-established technologies that provide high stabilization performance with relatively low weight, making them ideal for mobile use. In this study, we investigate the performance of a lightweight gimbal-based beam tracking system in an outdoor environment. Lasers with visible-wavelength and CMOS cameras were used as beacon beams and detectors to implement the tracking system. To compensate for the limited angular resolution of the gimbal, beam expansion of the beacon beam and appropriate design of fine tracking is incorporated. The results demonstrate the feasibility of using gimbal-based tracking systems for free-space QKD applications on mobile platforms.