China achieves 'spooky' quantum entanglement in space

The satellite, named Micius after an ancient Chinese philosopher, successfully transmitted entangled photons between three widely separated land-based stations.

James Smith | Jun 16, 2017

To try to create more secure internet communications than currently exist, last August China launched a $100 million satellite, known as the Quantum Experiments at Space Scale, in the Gobi Desert. Now, researchers from the Chinese Academy of Sciences have announced in a paper published Thursday in the journal Science that China's quantum satellite has achieved a successful result.

The satellite, named Micius after an ancient Chinese philosopher, successfully transmitted entangled photons between three widely separated land-based stations. It is the longest entanglement ever produced.

"It's a huge, major achievement," said Thomas Jennewein, a physicist at the University of Waterloo in Canada, in a report by Science. "They started with this bold idea and managed to do it."

Quantum entanglement, which physicist Albert Einstein famously called "spooky action at a distance," involves placing objects such as photons and electrons in a weird quantum state in which their quantum properties can be in multiple states at the same time. Entangled objects can then share these quantum properties even when separated by great distances.

The successful experiment was a critical test for the new technology of quantum cryptography, which uses quantum particles, such as photons or electrons, to transmit secure information.

On board the satellite is a complex system of mirrors and lasers, along with a special crystal, which produces 6 million pairs of photons at once. But researchers at the ground stations are able to detect only about one pair per second.

"It's a challenging task," says physicist Chao-Yang Lu, a professor at the University of Science and Technology of China, in a report by Wired. "It's like you have to clearly see a human hair from 300 meters away."

Next, Jian-Wei Pan and his former PhD supervisor at the University of Vienna, Anton Zeilinger, will collaborate to send entangled particles between whole continents.

"A future quantum internet will consist of fibre optic networks on the ground that will be connected to other fiber networks by satellites overhead," said Zeilinger, in a report by BBC News. "I think it will happen."

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