Advancements in deployed quantum communication networks

Quantum communication has established itself as a reliable and effective method of ensuring absolute confidentiality by exploiting quantum properties. We reached a significant milestone with the launch of the first quantum network connecting three European countries during the G20 meeting in Trieste. A reliable quantum key distribution (QKD) link using an undersea fibre-optic cable between the islands of Malta and Sicily was successfully implemented using an innovative room-temperature single-photon detector that outperformed standard detectors. We also implemented QKD in two terrestrial free-space links in the Florence area, demonstrating that time-bin, fibre-based QKD systems can be efficiently used for free-space communications links.