Scientists at the Max Planck Institute of Quantum Optics in Garching, Germany have successfully created the world’s first quatum network. A team of scientists led by Professor Gerhard Rempe, director at the institute and head of the Quantum Dynamics devision, set up the first elementary quantum network by coupling single-atom nodes that communicate quantum information via the coherent exchange of single photons. These nodes are prerequisites for functional quantum networks, as they allow for the reversible exchange of quantum information.

The group has been working for years on systems in which a single atom, using finely-tuned lasers, is embedded in an optical cavity composed of two highly-reflecting mirrors placed at a very short distance. The emission of photons from an atom inside one of these cavities can be directed in a controlled way. Using controlled emission of single photons from the trapped atom, the scientists were able to transfer information encoded in a single photon onto a second single photon after a certain storage time.

The milestone passed today was the connecting of two of these single-atom systems, and the exchange of quantum information between them. The scientists hope these single-atom-cavity nodes can be used in networks of larger size, and hope they will improve upon the performance and usefulness of “classical” networks.

“We were able to prove that the quantum states can be transferred much better than possible with any classical network,” said Dr. Stephan Ritter, leader of the experiment.

The scientists also succeeded in generating a quantum mechanical entanglement between the nodes. This means the polarization of each of the atoms was linked, even a a distance. The experiment was the world’s “largest” quantum system with massive particles.

“We have realized the first prototype of a quantum network”, said Ritter. “We achieved reversible exchange of quantum information between the nodes. Furthermore, we can generate remote entanglement between the two nodes and keep it for about 100 microseconds, whereas the generation of the entanglement takes only about one microsecond. Entanglement of two systems separated by a large distance is a fascinating phenomenon in itself. However, it could also serve as a resource for the teleportation of quantum information. One day, this might not only make it possible to communicate quantum information over very large distances, but might enable an entire quantum internet.”