A new record in the transport of an entanglement state between an atom and a photon on an optical fiber was achieved by physicists at the Ludwig-Maximilians-Universitaet (LMU) in Munich. With the help of colleagues from the University of Saarland, the researchers were able to successfully transport this state over a distance of 12 miles.

Entanglement is a particular state that is shared between two different particles. The latter are irrevocably connected and the connection does not depend on how far apart the same particles are. It is the “spectral action at a distance” as it was called by Alberta Einstein who did not understand how it works. Among other things, even today the phenomenon is not really understood but it is thought that it can still be exploited in the context of communications.

For some time scientists have already discovered that this state of connection between an atom and a photon can be transmitted over optical fiber, the kind used for telecommunications. Previously scientists had succeeded but only a distance of 700 meters.

This new experiment, with its success over a distance of 12 miles, is, according to the researchers themselves, “a milestone, because the distance covered confirms that quantum information can be distributed on a large scale with few losses,” as Harald Weinfurter, one of the scientists who took part in the project, explains.

The loss during transport is also minimized by the fact that conventional telecommunications networks travel over a wavelength of 1550 nanometres.

Now the researchers are planning to generate entanglement between two atoms and new nodes could be added to a growing network.