China moves closer to unhackable communications goal

China moves closer to unhackable communications goal
China has sent an “unbreakable” code from a satellite to the Earth, marking the first time space-to-ground quantum key distribution technology has been realised. Photo: Reuters
Published: 5:45 PM, August 10, 2017
Updated: 10:57 PM, August 10, 2017

BEIJING — Chinese scientists have sent the first quantum transmission from Earth to an orbiting satellite, marking another key step in the creation of an “unhackable” global communications network.

In a summary of their experiment published yesterday in the scientific journal Nature, the team, led by Mr Pan Jianwei, said the transmissions had travelled as far as 1,400km between base stations in central and western China and a satellite launched last year. “Previous (quantum) teleportation experiments between distant locations were limited to a distance of the order of 100km,” wrote the scientists.

Unlike traditional communications, which can be tapped surreptitiously, anyone attempting to eavesdrop on a quantum communication creates a disturbance that can be detected by the network’s users.

“China is now the world’s leader in quantum communication technologies and is actively co-operating with scientists from Austria, Germany and Italy in this field,” said Professor Peng Chengzhi, a member of the research team and a professor at the University of Science and Technology in Hefei, Anhui province. “China will lead the quantum space race for the next 
five years.”

Dr Tim Byrnes, a quantum physicist at New York University’s Shanghai campus, described the result as “truly remarkable”. He noted that before China’s successful experiments, including a transmission from space to Earth in June, the longest distance travelled by a quantum communication had been 143km.

Development of quantum communications on terrestrial networks has been impeded by the particles in the Earth’s atmosphere. According to Prof Peng, a quantum communication along fibre-optic cables between Beijing and Shanghai would require more than 30 transfer stations. “We need to decode the information and re-encrypt it at each station,” he said.

As a result, quantum physicists have turned their attention to space-based networks.

“These experiments show that you can really overcome this issue by going to space,” said Dr Byrnes. “The reason is simple — space is a vacuum and light can travel long distances unimpeded. The US, Europe and Japan have been trying to do this for years.”

The US$100 million (S$136 million) Micius satellite involved in the experiments was successfully launched in August 2016. It is named after an ancient Chinese philosopher and scientist.

Chinese scientists hope to launch a second quantum communications satellite by the summer of 2021.

Prof Ronald Hanson at the Technical University of Delft, in Holland, called yesterday’s announcement “a very important milestone”, but noted that technical hurdles remained. 

“We are still very far from making a global quantum network; this is not the last missing link,” said Prof Hanson. “Such satellite links would need to be linked with local quantum processors and memories — systems that we are working on.”

In July, Chinese scientists said they had successfully deployed a local-area quantum network in Jinan, in eastern Shandong province. The Jinan network will also be a key link in a 2,000km quantum network being built between Beijing and Shanghai. FINANCIAL TIMES