Entangled photon pair source for quantum communication#
Quantum Key Distribution (QKD) is the distribution of keys to sender and receiver for encrypting and decrypting data. The key information is carried by photons that are quantum mechanically entangled. This means that a pair of entangled photons, where one photon is going to the sender and the other to the receiver, cannot be eavesdropped by a third party without destroying the entanglement state, which can be observed by sender and receiver. QKD is thus believed to be the future of encrypted communication; it provides keys that are safe from being hacked by means of the laws of physics.
Due to the required long coherence length of entangled photons that can only currently be realized by free-space optics, satellite optical links are preferred to distribute keys over large distances to different customers. At Fraunhofer IOF, the prototype of a space-suitable Entangled Photon Source (EPS) has been developed for such satellite links within the framework of the European Space Agency ARTES telecom program.