Rapid process with new light sources
tubLAN Q.0 is also breaking new ground in terms of the light sources used to emit the photons. All quantum networks realized to date, such as those in Vienna, Cambridge (England), or Hefei (China), use lasers for this purpose. However, these do not emit the required single photons in all cases, but often groups of two or more. These cannot then be used to produce the quantum key, though, and thus reduce the transmission rate. "Since, after all, the keys used have to be just as long as the message itself, this slows down the process noticeably," says Heindel. "We will therefore, for the first time in a realistic network environment, use pure single-photon sources that actually emit only a single light particle at a time."
The research group headed by Prof. Dr. Stephan Reitzenstein at TU Berln is developing the single photon sources for the fiber optic network using the MDI-QKD method. For the open-air transmission, sources are being built in a collaboration between the University of Oldenburg, the University of Applied Sciences Emden / Leer, and the University of Jena. The simulation and theoretical modeling of the experimental results is carried out in collaboration with the junior research group led by Dr. Anna Pappa at TU Berlin, which is funded by the Emmy Noether Program of the German Research Foundation (DFG)