SoylentNews

upstart writes:

Researchers break world record for quantum-encrypted communications:

Researchers in Beijing have set a new quantum secure direct communication (QSDC) world record of 102.2 km (64 miles), smashing the previous mark of 18 km (11 miles), The Eurasian Times reported. Transmission speeds were extremely slow at 0.54 bits per second, but still good enough for text message and phone call encryption over a distance of 30 km (19 miles), wrote research lead Long Guilu in Nature. The work could eventually lead to hack-proof communication, as any eavesdropping attempt on a quantum line can be instantly detected.

[...] The same research team set the previous fiber record, and devised a "novel design of physical system with a new protocol" to achieve the longer distance. They simplified it by eliminating the "complicated active compensation subsystem" used in the previous model. "This enables an ultra-low quantum bit error rate (QBER) and the long-term stability against environmental noises."

As a result, the system can withstand much more so-called channel loss that makes it impossible to decode encrypted messages. That in turn allowed them to extend the fiber from 28.3km to the record 102.2 km distance. "The experiment shows that intercity quantum secure direct communication through the fiber is feasible with present-day technology," the team wrote in Nature.

Journal Reference:
Zhang, Haoran, Sun, Zhen, Qi, Ruoyang, et al. Realization of quantum secure direct communication over 100 km fiber with time-bin and phase quantum states [open], Light: Science & Applications (DOI: 10.1038/s41377-022-00769-w)

Original Submission