China's world-first quantum network spans 4,600km

BEIJING (China Daily/ANN): Chinese scientists have created the world's first integrated space-to-ground quantum network that can provide reliable, ultrasecure communication between more than 150 users over a total distance of 4,600km across the country, according to a study published in the journal Nature on Thursday (Jan 7).

Reviewers of the study hailed the achievement as "impressive" and "futuristic", as it is the largest of its kind in the world.

It also represents a major step toward building a practical, large-scale quantum internet, they added.

Quantum communication is widely regarded as the future of secured communication because it harnesses the strange properties of quantum mechanics to encrypt and relay data.

Therefore, it can be used to transfer information between banks, public infrastructure, government departments and other sectors where security is paramount, according to the University of Science and Technology of China in Hefei, Anhui province.

For example, the act of observing a particle can change how it behaves, therefore any attempt to eavesdrop on quantum communication will introduce anomalies to the transmission and be detected.

The core technology of quantum communication is quantum key distribution, which takes advantage of the quantum states of particles, such as photons, to produce a shared random secret key known only to the communicating parties, which can later be used to encrypt and decrypt messages.

In the integrated network, scientists from the USTC combined 700 ground-based optical fibres and two ground-to-satellite links to create a quantum communication network spanning over 4,600km.

The fibre network, which stretches from Beijing to Shanghai and has key operation centres in Hefei and Jinan, Shandong province, is 2,000km in length and connects over 150 industrial users along the line, according to the study.

These users included State and local banks, municipal power grids and government agencies.

The satellite-to-ground links connect a ground observatory station in Xinglong, Hebei province, with another station in Nanshan, Xinjiang Uygur autonomous region, over a distance of 2,600km.

The Chinese team said it will further expand the quantum network in China, and it will continue collaborating with peers from Austria, Italy, Russia and Canada.

It hopes to build a bigger integrated space-to-ground quantum network via a constellation of smaller, more cost-efficient quantum communication satellites and ground-based receivers.

It will also create medium and high-Earth-orbit satellites capable of quantum communication across tens of thousands of kilometres, which can be used to further test the feasibility of a global quantum internet, as well as conduct large-scale experiments in quantum mechanics.