Boost for the quantum internet

Quantum networks link quantum devices together for secure communication and powerful sensor networks. Photons carry quantum information through optical waveguides, but can be lost over long distances. Quantum repeaters, developed 25 years ago by Briegel, Dür, Cirac, and Zoller, use entanglement sources and memories to distribute entanglement between network links, enabling long-distance connections.

Even transmission over 800 kilometers possible

Quantum physicists at the University of Innsbruck, led by Ben Lanyon, have built a working quantum repeater. This network node utilizes two matter systems to create entanglement with a photon at the standard telecom frequency and perform entanglement swapping operations. The repeater, comprised of calcium ions within an ion trap and an optical resonator, enables quantum information transfer over a 50-kilometer optical fiber. The researchers aim to enhance the design to achieve transmission over 800 kilometers, connecting Innsbruck to Vienna.

The findings were published in Physical Review Letters, with funding from various sources including the Austrian Science Fund FWF, the Austrian Academy of Sciences, and the European Union. Lanyon’s team is affiliated with the Quantum Internet Alliance, an international project under the EU Quantum Flagship.