How can data be transmitted securely? A question that is becoming increasingly urgent in today's digital world for public authorities and companies, especially in the context of industry 4.0, and also for private individuals. What is needed are solutions that meet the security requirements of years and decades to come. Quantum encryption stands out in particular. It enables the security of data transmission to be traced back to the validity of fundamental laws of quantum physics.

The QuNET (Quantum Network) research initiative is dedicated to this goal, within the framework of which the participating partners are creating a national quantum network. On 12 November 2019, the kick-off of the first QuNET project phase of the research initiative took place. The German Aerospace Center (DLR) is working on practical solutions for satellite-based quantum communication in order to safely agree on keys over long distances. So far, this has only been possible over a few 100 kilometres. Using satellites, on the other hand, keys can in principle be agreed between any location on Earth. This is no trivial undertaking: Since quantum communication protocols require the handling of individual photons, the transmission must be very efficient, i.e. as many of the photons as possible must contribute to key generation. In addition, foreign radiation must be avoided. The atmosphere is disturbing both in terms of density fluctuations and scattering processes.