In the study “Coherent phase transfer for real-world twin-field quantum key distribution”, published on the Nature Communications, a team of INRiM researchers shows that coherent laser interferometry considerably improves the performances of quantum key distribution protocols in long-distance, real-world networks.
Quantum Key Distribution (QKD) protocols enable cryptographic keys to be shared between distant parties with an intrinsic security guaranteed by the laws of quantum mechanics. This is made possible by the transmission of single photons, the elementary particles of which light is made of.
The issue is particularly topical and the European Union, thanks to the OQTAVO project (in which INRiM is actively involved), aims to integrate quantum technologies for cryptography within specific services throughout the Union.
However, one of the main obstacles towards the realization of a long-reach quantum network is the “fragility” of quantum signals.
Tuttavia, uno dei maggiori ostacoli allo sviluppo efficace in campo reale e su lunghe distanze di queste tecnologie è dovuto alla “fragilità” dei segnali quantistici scambiati.
In this regard, INRiM has shown that, by combining sinergic exploitation of coherent laser interferometry, single-photon technologies and quantum metrology, it is possible to improve the information contained in single photon states, allowing lower error rates and increasing the length of exchanged messages. These improvements pave the way for more efficient QKD protocols exploiting the twin-field quantum key distribution technique, which is currently seen as the most promising candidate for long-reach quantum networks.
The experiment, conducted along a 200 km span of the Italian Quantum Backbone, a 1800 km infrastructure developed by INRiM, is also the result of a collaboration with Toshiba Europe, leading company in the development of commercial quantum technology products, and the network provider TOP-IX Consortium, active throughout northern Italy, that dedicated part of its infrastructure to this research.