In many ways, digital transformation has highly increased the necessity of reliably protecting communication. Quantum communication provides novel means for future-proof long-term protection of communication even against eavesdropping attacks with quantum computers by generating and distributing cryptographic keys with security based on fundamental laws of quantum physics. However, to date the maximum distance for quantum communication is limited to around 100 km due to transmission losses. In order to overcome these limits, quantum repeaters are necessary that enable longer quantum communication distances.
In the scope of the project “QuantumRepeater.Link” (QR.X), the Fraunhofer Heinrich Hertz Institute, together with its 25 partners from academic research and industry, will work on a first realization of such quantum repeater links. Therefore, HHI will implement a 3-node quantum communication testbed comprising a photonic quantum state source and two quantum receivers. Furthermore, a fiber-coupled free space optical link will enable transparent coupling between fiber and free space segments of the test infrastructure. By spectral multiplexing, we aim at increasing the capacity of quantum links and anticipate complex network topologies. All technological building blocks will be used for demonstrating and evaluating practical test cases including quantum teleportation, 3-point QKD and multiplexed quantum communication.