Continuous entanglement distribution over a transnational 248 km fiber link.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 36253474.
- Also identified by DOI 10.1038/s41467-022-33919-0 and PMC identifier 9576737.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Reliable long-distance distribution of entanglement is a key technique for many quantum applications, most notably quantum key distribution. Here, we present a continuously working, trusted-node free international link between Austria and Slovakia, directly distributing polarization-entangled photon pairs via 248 km of deployed telecommunication fiber. Despite 79 dB loss, we observe stable detected pair rates of 9 s-1 over 110 h. We mitigate multi-pair detections with strict temporal filtering, enabled by nonlocal compensation of chromatic dispersion and superconducting nanowire detectors. Fully automatized active polarization stabilization keeps the entangled state's visibility at 86% for altogether 82 h. In a quantum cryptography context, this corresponds to an asymptotic secure key rate of 1.4 bits/s and 258 kbit of total key, considering finite-key effects. Our work paves the way for low-maintenance, ultra-stable quantum communication over long distances, independent of weather conditions and time of day, thus constituting an important step towards the quantum internet.