October 17 2025 -- The QuNET initiative, which develops technologies for quantum-secure communication, successfully completed its latest key experiment in mid-October. As part of a flight experiment between Oberpfaffenhofen and Erlangen, a research aircraft (model: Dornier 228) operated by the Deutsche Zentrum für Luft- und Raumfahrt (DLR) served as a mobile node within a Quantum Network. On board was an integrated photon-pair source for generating entangled light particles, establishing a connection to an optical ground station. The ground station – a mobile container with an integrated receiving terminal, known as the QuBUS – was provided by the Fraunhofer-Institut für Angewandte Optik und Feinmechanik (IOF) in Jena. A specialized tracking system ensured that the receiving terminal continuously followed the aircraft’s movement and maintained a stable optical link. Compensating for atmospheric turbulence and disturbances posed a significant technical challenge, as did handling single photons, whose generation, detection, and wavelength tuning require utmost precision.

During the course of the experiment, the researchers were able to measure several different Quantum Channels between the aircraft and the ground station, transmit photons to an ion trap, and test new technologies for Quantum Key Distribution (QKD). QKD is considered a key technology for the quantum-secure communication of the future, as it enables the protection of critical infrastructures and sensitive data even in the age of powerful Quantum Computers. The experiment involved researchers from the DLR, Max-Planck-Instituts für die Physik des Lichts (MPL), the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), as well as the Fraunhofer Institutes Angewandte Optik und Feinmechanik (IOF) in Jena and Nachrichtentechnik, Heinrich-Hertz-Institut (HHI), in Berlin.

The technologies demonstrated during the flight experiment represent an important step toward Future Quantum Networks. To bridge long distances, satellites, aircraft, and other mobile platforms are expected to serve as key components of such networks in the future.