Quantum communication is the transmission of quantum states from one place to another. This forms the basis for a variety of applications, such as quantum key distribution or the networking of quantum computers.
Our research group handles quantum communication systems from their initial concept all the way to the implementation of large-scale experiments with satellites and aircrafts. Special focus is on the analytical and metrological channel characterization, design of the individual photonic links, as well as the development of the ground stations and the flight terminals. We particularly concentrate on the technological challenges in the field of optics and photonics design.
We also operate the special laboratories "Optical Ground Station Oberpfaffenhofen" (OGSOP) and "Transportable Optical Ground Station" (TOGS), which are important facilities to support our satellite and aircraft experiments concerning quantum and telecommunications.
The currently most important and technologically advanced application of quantum communication is quantum key distribution, which is a central research field of our group. Tap-proof cryptographic procedures are indispensable for the digital exchange of confidential data, but the currently established asymmetric cryptographic algorithms cannot withstand the powerful attacks of future quantum computers. The solution to this problem is the exchange of secure quantum keys between communication partners for the use of symmetric-key encryption. However, the transmission of quantum states via glass fibers is limited to a few hundred kilometers due to the channel attenuation. In order to enable transmission over great distances, we and our scientific and industrial partners are working together on new methods for the distribution of quantum keys via satellites. With our established know-how in the field of free-space optical communications, we work on quantum cryptographic systems that enable verifiably secure data encryption across entire continents by the use of satellites.
A further field of application is the transmission of quantum states for the networking of quantum computers or simulators to enable future quantum networks. The dissemination of of entangled states is an important element here, where satellite systems can be used to overcome long distances.