Development of laser terminals for satellite-based QKD on CubeSat platforms

Kurzfassung

Satellite-based Quantum Key Distribution (QKD) plays an important role in future quantum safe networks to overcome the limited transmission range of fiber based QKD. Recent missions demonstrated the feasibility of this technique paving the way for future projects. CubeSats provide a cost-efficient way for testing new QKD technologies in space and pose a promising and scalable platform for future constellation. The DLR Institute of Communication and Navigation (DLR-KN) develops terminals for satellite QKD systems. Within the scope of the project QUBE, a 1/3U sized terminal is developed for space-to-ground QKD experiments. The terminal will set up a multi wavelength downlink, providing a classical synchronization and a quantum channel. Its functionality is verified in a ground-to-ground link and the launch of the 3U CubeSat is planned for 2024. During the mission, core technologies for future QKD technologies are tested in space. Follow up projects at DLR-KN aim at the development and integration of bigger telescopes in CubeSats leading to an increased antenna gain, enabling full QKD implementation. Based on the QUBE system, a terminal breadboard with an aperture diameter of 85mm is developed within the QuNET project. The paper presents an overview of the system concept, a detailed insight into the optics design, the concept for the optomechanics and the implementation of the pointing assembly. The parallel development of the subsequent QUBE-II terminal exploits the gathered experience and lessons learned from the QUBE mission and QuNET breadboard development. The QUBE-II terminal will enable full space-to-ground QKD implementation with a CubeSat and will additionally provide an optical data up- and downlink. QUBE-II will be launched at the end of 2025.