Phys.org July 7, 2022
To fully use entanglement over long-distance quantum network links it is mandatory to know it is available at the nodes before the entangled state decays. An international team of researchers (Austria, Germany) demonstrated entanglement between two independently trapped single rubidium atoms generated over fibre links with a length up to 33 km. They generated atom–photon entanglement in two nodes located in buildings 400 m line-of-sight apart and to overcome high-attenuation losses in the fibres converted the photons to telecom wavelength using polarization-preserving quantum frequency conversion. The long fibres guided the photons to a Bell-state measurement setup in which a successful photonic projection measurement showed the entanglement of the atoms. According to the researchers their results show the feasibility of entanglement distribution over telecom fibre links useful, for example, for device-independent quantum key distribution and quantum repeater protocols. The work represents an important step towards the realization of large-scale quantum network links…read more. Open Access TECHNICAL ARTICLE
Schematic of the experimental setup. Credit: Nature volume 607, pages69–73 (2022)Â