Chinese scientists announce quantum secure direct communication over 100 km fibre

The Beijing Academy of Quantum Information Sciences and the Tsinghua University in China have announced that a team of researchers developed a new quantum secure direct communication (QSDC) system that can communicate at 22.4 Kbps through about 30 km commercial fibre and at 0.54 bps through 100 km ultra-low loss fibre. QSDC allows the transmission of information securely and directly using quantum states. According to the Beijing Academy, the new system enables communications between cities point-to-point and in arbitrarily long-distance, and it lays ‘a solid basis to support global quantum network and relevant applications’. The system, which uses time-bin states for eavesdropping detection and phase states for communicating the message, is described as providing ‘a very high stability and a very low intrinsic error rate (the error rate when there are no eavesdroppers)’.