Construction of First Telecommunications Network Remote Quantum Relay Node

The quantum physics research team of Innsbruck University in Austria has successfully constructed a quantum repeater node for the standard wavelength of the telecommunications network and transmitted quantum information for tens of kilometers. This fully functional network node is the core part of a quantum repeater, consisting of two single material systems that can generate entanglement in the frequency and entanglement exchange operation of a standard photon entanglement telecommunications network. The research results are published in the new issue of the Physical Review Letters.
Quantum networks connect quantum processors or quantum sensors to each other. Between network nodes, quantum information is exchanged by photons passing through optical waveguides. However, the possibility of photon loss increases sharply over long distances.

Quantum information cannot be simply copied and amplified. 25 years ago, the research team of Innsbruck University provided a blueprint for quantum repeaters. It has an optical material entanglement source and memory to generate entanglement in independent network links, which are connected between them through entanglement exchange and ultimately distribute the entanglement over long distances.
The newly constructed repeater node consists of two calcium ions captured in the ion trap inside the optical resonator and a single photon conversion to the electrical wavelength. The scientists also showed that quantum information is transmitted through a 50km long optical fiber, and the quantum repeater is located in the middle between the starting point and the end point.
The researchers also calculated which improvements to this design were necessary to make transmission over 800 kilometers possible, thereby connecting Innsbruck and Vienna.