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Three major scientific goals achieved by China’s quantum satellite: CAS

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Updated: 09:00 GMT, Aug 10, 2017 | Published: 06:07 GMT, Aug 10, 2017 |
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The world’s first quantum satellite has achieved three pre-set major scientific objectives, the Chinese Academy of Sciences (CAS) announced last week.

Chinese scientists have become the first in the world to realize the quantum key distribution from a satellite to the ground, and the ground-to-space quantum teleportation after realizing the satellite-based distribution of entangled photon pairs over 1,200 kilometers in June.

The results marked the completion of the three major scientific breakthroughs in quantum experiments, said Pan Jianwei, principal researcher of the Quantum Experiments at Space Scale (QUESS) and an academician of the CAS, at a news briefing in Beijing on Aug 4.

“We’re very pleased. We have completed all the targets of this scientific experiment within one year, which we had anticipated to finish in two years,” said Pan Jianwei.

Pan explained more details on the recent achievements.

He said the satellite has sent quantum keys to ground stations in Xinglong, in north China’s Hebei Province, and Nanshan near Urumqi, capital of northwest China’s Xinjiang Uygur Autonomous Region.

Communication distance between the satellite and the ground stations varied from 645 km to 1,200 km, and the quantum key transmission rate from satellite to ground is up to 20 orders of magnitude more efficient than that expected using an optical fiber of the same length, said Pan.

In the experiment of quantum teleportation, the scientists transmitted quantum states of photons from a ground station about 5,100 meters above sea level in Ali Prefecture, southwest China’s Tibet Autonomous Region, to the satellite 500 km above.

To optimize the link efficiency and overcome the atmospheric turbulence, a series of techniques were developed, including a compact ultra-bright source of multi-photon entanglement, narrow beam divergence, and high-bandwidth and high-accuracy acquisition, pointing and tracking, according to Pan.

This work established the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward a global-scale quantum internet, the scientist said.

The satellite, named “Micius,” was launched by China on August 16, 2016.

The achievements based on experiments conducted with the world’s first quantum satellite, Quantum Experiments at Space Scale (QUESS), were published in the online academic journal Nature on Thursday.

The Nature reviewers commented that the experiment was an impressive achievement, and constituted a milestone in the field.

“With the publication of these two new papers, Professor Jianwei Pan and his colleagues have completed their demonstration of a trio in the physical sciences. This group has been able to push research in practical quantum communication technologies to such an astronomical height,” said Karl Ziemelis, chief physical sciences editor of the Nature.