China achieves 300-km quantum secure direct communication which compliments earlier breakthroughs.
Chinese researchers have made a significant advancement in quantum communication by establishing a quantum secure direct communication (QSDC) network covering nearly 300 kilometers, marking a practical range for inter-city use.
Led by scientists from Shanghai Jiao Tong University, the project maintained a quantum state fidelity of over 85 percent during transmissions between users, according to the Science and Technology Daily.
Published in Science Bulletin, the study tackles major challenges in quantum networking, especially in terms of long-distance transmission and accommodating multiple users.
The team built a double-pumped, scalable, and fully connected QSDC network capable of operating in noisy conditions. It maintained a stable photon pair rate of 300 to 400 Hz, which theoretically supports communication at several bits per second.
This follows a record-setting quantum direct communication test in February by a Beijing team that achieved a 104.8 km transmission using regular optical fiber.
Originally introduced by researchers at Tsinghua University, QSDC allows secure communication using quantum states. Its advantages include eavesdropping resistance, compatibility with existing systems, simplified operation, and discreet data transfer.
QSDC systems are expected to serve sectors requiring top-level data security, such as the financial industry.
The technology complements another key form of quantum communication known as quantum key distribution (QKD). Together, they could form the infrastructure for a future global quantum internet.
In a world-first achievement, a global team led by Chinese scientists successfully carried out real-time QKD communication over 12,900 kilometers between China and South Africa via satellite.
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