Chinese scientists have successfully implemented a new way of quantum key distribution (QKD) which can boost the speed of intercity quantum networks.

Quantum network is known for its strong resistance against eavesdropping—theoretically, it's completely hacker-free. Data transferred through this kind of network is encrypted, with the decryption key transferred through quantum mechanics.

Current QKD methods have limited distances and can be challenging to implement, but the new method demonstrated hope to solve these problems.

The new method, named mode-pairing QKD (MP-QKD), was first proposed in 2022 by a research team led by Dr. Ma Xiongmeng at Tsinghua University. It does not require a technically challenging step called "phase locking" to be implemented.

The team cooperated with another team led by Professor Pan Jianwei, a pioneer in quantum communication in China, to put the new method into practice, and the performance was outstanding.

Details of the test were published in the scientific journal Physical Review Letters.

In the paper, the researchers said MP-QKD can achieve a "quadratic improvement" in key-rate—basically the speed of QKD—over traditional measurement-device-independent QKD (MDI-QKD) when used in metropolitan and intercity networks.

The new method also performs faster on longer distances like 300 to 400 kilometers, with a speed boost by three orders of magnitude, the paper said.

The paper added that MP-QKD can be achieved with "off-the-shelf lasers," thus is a "ready-to-implement" technology.

The scientists expect the new technology to be "widely used" in future intercity quantum networks.