China achieves tamper-proof quantum communication over 100km with single atoms

Chinese researchers have pushed the frontiers of quantum encryption, demonstrating a powerful new way to send secure information over more than 100km (62 miles) of optical fibre – without having to trust the equipment being used.

A team led by Pan Jianwei at the University of Science and Technology of China used a pair of individual rubidium atoms, trapped in laser beams at two separate network nodes, as the foundation for their system, according to a paper published in Science this week.

The researchers created quantum links between the atoms using single light particles, or photons. By comparing the atoms’ states at each end, the team generated identical strings of 0s and 1s – a shared secret key for encryption.

What sets the experiment apart is that the approach, known as device-independent quantum key distribution (DI-QKD), would still work securely even if the devices were flawed or had been tampered with.

The method derives its security from the quantum-mechanical behaviour of the entangled atoms, protecting against the real-world vulnerabilities that have long challenged quantum communication systems.

DI-QKD had previously only been demonstrated over short distances in the laboratory, the researchers wrote, adding that their study helped to “close the gap between proof-of-principle experiments and real-world applications”.

South China Morning Post