The distance between the orbiting satellite and these ground stations varies from 500 to 2,000km. The feat showed that the particles of light can retain a odd type of interconnectedness, known as quantum entanglement, even when flung to opposite ends of a country, researchers from China report in the June 16 Science.
The distance record in both media had been about 100 km. The result is an outstanding landmark in the human history of communication and physical science, and reaches far and more. Now, a new study shows a successful transmission of the entangled photons between suborbital space and Earth.
While China is behind United States and Russian Federation in terms of space technology, the U.S. Defense Department has expressed concern that it will utilize its space technology to prevent rival countries from using space-based assets in the event of a crisis, as reported by Space Intel Report.
Chinese scientists claim to have taken an important step towards the creation of "unhackable" communications, transmitting a quantum signal 1,200km from China's communications satellite Micius to Earth, much further than the 100 km achieved before.
"For quantum networking, in this work, we have already achieved a two-photon entanglement distribution efficiency a trillion times more efficient than using the best telecommunication fibers", says Jian-Wei Pan, lead researcher on the project.
In theory, entangled particles should remain linked at any separation. In order to exploit this advantage, the scientists used a laser-based entangled-photon source especially resistance to disturbance.
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But despite China's latest achievement, the effort to build a useable quantum communications network still has a long way to go.
Norbert Lütkenhaus, a professor at the Institute for Quantum Computing at the University of Waterloo in Canada informed, "This is the first time you have a quantum channel between a satellite and the ground that you can actually use". However, this introduces the risk of collision with ordinary particles disrupting the delicate quantum states of our entangled photons.
Regarding quantum networking or internet, Jennewein described Thursday's quantum experiment result as "a very important milestone, because disseminating quantum entanglement is a first (and most important) building block".
"When I had the idea of doing this in 2003, many people thought it was a insane idea", Pan told the BBC World Service "Because it was very challenging already doing the sophisticated quantum optics experiments in a lab - so how can you do a similar experiment at a thousand-kilometre distance and with optical elements moving at a speed of 8km/s?"
"Going forward, it is not very hard to speculate that we will see the distribution of quantum entanglement on a global scale one day", said Jennewein.
Despite the long round-trip, the photons maintained their entanglement and were successfully received by the ground stations that were over a thousand kilometres apart. To confirm that the particles were entangled, and that the weird qualities of quantum mechanics held, the researchers used the photon pairs to perform a Bell test (SN: 9/19/15, p. 12), which analyzes correlations between the two particles.