China details its quantum key distribution network

Test used Micius satellite as platform for quantum key distribution

Scientists in China have offered another glimpse into their highly anticipated satellite quantum key distribution network, which is currently being tested.

Liao Shengkai, from the University of Science and Technology of China, and a team of technologists have published an academic paper on the topic in science publication, Physical Review Letters.

They detail an experiment that saw them send a range of quantum-based keys from China's Xinglong county to Graz in Austria in what they claim is a groundbreaking achievement for the project.

Quantum key distribution has become a popular topic in the cyber security world, tapping into quantum entanglement to enable vastly more secure communications - just as quantum computing threatens to render traditional encryption technology redundant.

The quantum keys are groundbreaking because they prevent eavesdropping, so they could be used by governments and other organisations when distributing sensitive information.

"We perform decoy-state quantum key distribution between a low-Earth-orbit satellite and multiple ground stations located in Xinglong, Nanshan, and Graz, which establish satellite-to-ground secure keys," wrote the researchers.

In this experiment, the researchers used transmitted images, as well as a 75-minute video conference that took place on 29 September 2017. They were secured using quantum keys.

China has tested similar technologies in the past. When it launched the Micius satellite in 2016, Chinese officials created entangled particles for encryption keys.

And last June, China was able to conduct space-to-ground entanglement and maintained its record for enabling engagement over 1,200 kilometres.

"These keys are then used for intercontinental quantum-secured communication. This was, on the one hand, the transmission of images in a one-time pad configuration from China to Austria as well as from Austria to China," explained the researchers.

The researchers used an Austrian node to demonstrate the distance that these keys can travel. They were able to travel between stations that were spread over 7,600 km.

They added: "Our work clearly confirms the Micius satellite as a robust platform for quantum key distribution with different ground stations on Earth, and points towards an efficient solution for an ultra-long-distance global quantum network.

The experiments are one of a number into quantum cryptography and networking being conducted in China.