Saturday, June 17, 2017

China's Quantum Satellite Achieves 'Spooky Action' at Record Distance

Photo taken on Nov. 26, 2016 shows a quantum communication ground station in Xinglong, north China's Hebei Province. Chinese scientists on Thursday reported a major breakthrough in quantum communication: A pair of entangled photons over a distance of 1,200 km have been successfully transmitted from space to Earth. The previous record was about 100 km. (Xinhua/Jin Liwang)

A team of Chinese scientists have realized the satellite-based distribution of entangled photon pairs over 1,200 kilometers. The photon pairs were demonstrated to be still entangled after travelling long distances. The experiment shows quantum entanglement, described by Albert Einstein as a "spooky action", still exists at such a distance.

This satellite-based technology opens up bright prospects for both practical quantum communications and fundamental quantum optics experiments at distances previously inaccessible on the ground, said Pan Jianwei, an academician of the Chinese Academy of Sciences.

The achievement was made with the world's first quantum satellite, Quantum Experiments at Space Scale (QUESS); also dubbed Micius, launched by China on August 16, 2016, and was published as a cover article in the latest issue of academic journal Science.

This experiment was made through two satellite-to-ground downlinks with a total length varying from 1,600 to 2,400 kilometers. The obtained link efficiency is many times higher than that of the direct bidirectional transmission of the two photons through telecommunication fibers, said Pan, who is also the lead scientist of QUESS.

Quantum entanglement is a phenomenon in quantum physics, which is so confounding that Albert Einstein described it as a "spooky action at a distance" in 1948.

Scientists found that when two entangled particles are separated, one particle can somehow affect the action of the far-off twin instantly.

Scientists liken it to two pieces of paper that are distant from each other: if you write on one, the other immediately shows your writing.

The mystery of quantum entanglement has been puzzling scientists since it was detected.

Quantum physicists have a fundamental interest in distributing entangled particles over increasingly long distances and studying the behavior of entanglement under extreme conditions.

In theory, this bizarre connection can exist over any distance, but scientists want to see if there's some physical limit. "If you want to explore new physics, you must push the limits," Pan said.

"Will gravity affect quantum entanglement? It needs long-distance experiment to test the different models. Although QUESS cannot test quantum gravity theories yet, we have developed the technologies needed for space-based experiments through this project," Pan said.

Credit: xinhuanet.com

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