In a milestone for secure communications, a research team from Shanghai Jiao Tong University has rolled out a quantum secure direct communication (QSDC) network stretching roughly 300 kilometers – a range that brings inter-city quantum links into practical use. Published in Science Bulletin and reported by Science and Technology Daily, the project shatters previous limits on transmission distance and user capacity.
By preserving more than 85% of quantum state fidelity between user pairs, this system shows that quantum states can survive across real-world fiber networks. The network’s double-pumped, fully connected design keeps signals stable even amid noisy environments, achieving a steady photon pair emission of 300–400 Hz. In theory, that translates to a few bits per second of ultra-secure data transfer.
This achievement builds on an earlier February record, when a Beijing-based team pushed quantum direct communication over 104.8 km of standard optical fiber. The concept of QSDC, first put forward by researchers at Tsinghua University, bypasses the need for keys by sending information directly via quantum states, with built-in eavesdropping checks and compatibility with existing infrastructure.
With its streamlined management and covert transmission features, QSDC is poised to serve sectors demanding top-tier security, such as finance and government. Together with quantum key distribution (QKD), these breakthroughs could form the bones of a future global quantum internet.
An international collaboration led by scientists from the Chinese mainland used a satellite link to demonstrate real-time QKD over more than 12,900 km between the Chinese mainland and South Africa, proof that quantum links can span the globe.
Reference(s):
cgtn.com
