For the first time, researchers have succeeded in creating strong coupling between quantum systems over a great distance. They accomplished this with a novel method in which a laser loop connects the systems, enabling nearly lossless exchange of information and strong interaction between them. In the journal Science, physicists from the University of Basel and University of Hanover reported that the new method opens up new possibilities in quantum networks and quantum sensor technology.

Quantum technology is currently one of the most active fields of research worldwide. It takes advantage of the special properties of quantum mechanical states of atoms, light, or nanostructures to develop, for example, novel sensors for medicine and navigation, networks for information processing and powerful simulators for materials sciences. Generating these quantum states normally requires a strong interaction between the systems involved, such as between several atoms or nanostructures.

Until now, however, sufficiently strong interactions were limited to short distances. Typically, two systems had to be placed close to each other on the same chip at low temperatures or in the same vacuum chamber, where they interact via electrostatic or magnetostatic forces. Coupling them across larger distances, however, is required for many applications such as quantum networks or certain types of sensors.