QuNET & MOBIXHAP - Mobile Nodes for Quantum Communication

The project "Mobile Node" (QuNET+MOBIXHAP) aims at developing and demonstrating a high altitude platform (HAP) for free beam based quantum key distribution. The method of key distribution using light quanta, known as quantum key distribution (QKD), is a promising approach because, due to fundamental physical laws, quantum keys cannot be intercepted and copied unnoticed. QKD technology can be used in fiber-based terrestrial communication networks as well as in free-space systems. However, for longer transmission distances, free-beam-based transmission of quantum keys using satellites or high-altitude platforms is advantageous. The overall system should be able to operate autonomously and withstand interference as well as adverse operating conditions in the stratosphere.

The IPMS supports the development of the requirements for the overall system with regard to the framework conditions of the HAP. This results in a system concept focusing on the Payload Management Unit (PMU) and its interconnectivity within the HAP and its impact on the other components of the HAP. Specific aspects of the PMU, such as Payload Network, System Network, Control Core Integration, Optical Extension Interface and Control Software are also highlighted here.

In a next step, microcontrollers will be integrated with network components that ensure precise time synchronization among the system components of the mobile nodes in addition to communication. For this purpose, the existing IP solutions at Fraunhofer IPMS can be used. The PMU also implements control and monitoring tasks in the system. Then, the expected parameters for the optical link (so-called link budgets) are determined for specific scenarios. From this, quantum key generation rates can be calculated for the various protocols and sources. The performance of the system interfaces HAPS - HAPS and HAPS - ground station are demonstrated in a 3 node network demonstrator.

Finally, derived from the HAPS specifications, the system design for the overall test setup of the HAPS subsystem will be developed. This includes all tests for the demonstration of the quantum key distribution as well as all pre-tests. The focus of Fraunhofer IPMS is to support the integration of the PMU and the interaction with all connected components in the HAPS.