Quantum networks have long been a top priority for researchers seeking to improve national security and minimize cyberthreats.

Such quantum networks connect quantum processors with each other. This allows secure, untappable communication.

However, creating real world long-distance versions of these networks is a daunting task.

Between network local nodes, quantum information is exchanged by photons that travel through optical waveguides.

But over long distances, the likelihood of photons being lost increases dramatically. 

In response to the fact that quantum information cannot simply be copied and amplified, researchers at the University of Innsbruck provided the blue prints for a quantum repeater, 25 years ago.

These plans featured light-matter entanglement sources and memories to create entanglement in independent network links that are connected between them by a so-called “entanglement swap” enabling entanglement distribution over long distances.

Recently, a new generation of quantum physicists at the University of Innsbruck succeeded in building a fully functioning network node made with two single matter systems enabling entanglement creation with a photon at the standard frequency of the telecommunications network and entanglement swap ping operations.

The repeater node consists of two calcium ions captured in an ion trap within an optical resonator as well as single photon conversion to the telecom wavelength.

The scientists thus demonstrated the trans fer of quantum information over a 50-kilometer-long optical fiber, with the quantum repeater placed exactly halfway between the starting and end points.

The researchers were also able to identify improvements of this de sign that would be necessary to make trans mission up to 800 kilometers possible.

The breakthrough results were just published in the journal, Physical Review Letters.