Encrypted quantum keys sent a record-breaking 421 km in optical fibre

Encrypted quantum keys have been sent across a record-breaking 421 km of optical fibre at the fastest data rate ever achieved for long-distance transmission. Alberto Boaron and colleagues at University of Geneva and ID Quantique in Switzerland and Corning in the US achieved this feat by modifying the detectors used for quantum key distribution (QKD) to minimize noise. Their experiment represents a significant advance in the secure exchange of quantum information.