Quantum Networks in Space
Lisa Wörner · 2023
The inherent properties of quantum mechanics render it an important subject for fundamental research and applications alike. Entanglement stands out among those, allowing for novel secure communication and more rapid computation. To enable global secure communication, space based networks are required. A space network with trusted nodes for every user is an unviable feat, and could lead, given the amount of potential civil, governmental, and military users, to a cluttering of space. Additionally, global networks of trusted nodes exclude smaller to medium players from profiting from the quantum revolution and the benefits of secure communication. To remain inclusive to small businesses and enable broad usage of the technology, the operation of untrusted nodes in space is inevitable. Consequently, untrusted nodes need to be capable of receiving and re-transmitting the information with the possibility of storage of the information in-between. Hence, space-based quantum repeater, consisting of a receiver, a transmitter, and a coherent memory, could operate as untrusted nodes. In this chapter, the challenges, necessities, and opportunities for global quantum networks will be discussed. This includes novel techniques for quantum repeater and their current technology readiness level.