[Xinhua] Chinese scientists conduct ground-to-space quantum teleportation


"Beam me up, Scotty." The famous "Star Trek" catchphrase has launched teleporting daydreams the world over.

Now Chinese scientists have completed an experiment straight out of the realms of science fiction - quantum teleportation - from the ground to the world's first quantum satellite.

The experiment was similar in some ways to the Star Trek mode of transport, except that the scientists beamed up the quantum states of photons rather than people.

The results of the quantum teleportation experiment - Quantum Experiments at Space Scale (QUESS) - via the quantum satellite was published in the latest issue of the academic journal Nature.

The satellite is named "Micius" after a 5th century B.C. Chinese philosopher and scientist who is credited as the first person ever to conduct optical experiments

The reviewers of Nature commented that the results represent an important breakthrough in the quest for quantum communication over long distances. This goal is very challenging and new.

Pan Jianwei, lead scientist of QUESS and an academician of the Chinese Academy of Sciences, explained that quantum teleportation allows faithful transfer of unknown quantum states from one object to another over a long distance, without physical travel of the object itself. Long-distance teleportation has been recognized as a fundamental element in protocols such as large-scale quantum networks and distributed quantum computation.

However, previous teleportation experiments between distant locations were limited to a distance of about 100 kilometers, due to photon loss in optical fibers or terrestrial free-space channels. An outstanding challenge for building a global-scale "quantum internet" is to significantly extend the range for teleportation, Pan said.

A promising solution to this problem is exploiting satellite platforms and space-based links, which can conveniently connect two remote points on Earth while greatly reducing channel loss, because most of the photons' transmission path is in empty space, said Pan.

In the experiment, 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, 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, Pan said.

Quantum physics is the study of the universe's basic building blocks at a scale smaller than atoms. These tiny particles behave in a way that could overturn assumptions of how the world works.

Entanglement is one of the strange properties of quantum physics. It so confounded Albert Einstein that he described it as "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 at a speed faster than light.

This magic-like connection has inspired the idea of quantum teleportation.

The first paper expounding the idea of quantum teleportation was published by six physicians in 1993.

In 1997, Austrian quantum physicist Anton Zeilinger, tutor of Pan Jianwei, succeeded in the first experimental verification of quantum teleportation. Since then, scientists have demonstrated quantum teleportation with different physical systems such as atoms, ions, electrons and superconducting circuits.

Meanwhile, the limit for quantum teleportation is constantly expanding.

Pan's research team was awarded the Physics World 2015 Breakthrough of the Year "for being the first to achieve the simultaneous quantum teleportation of two inherent properties of a fundamental particle - the photon," according to PhysicsWorld.com.

Pan regards the achievement as a step toward the teleportation of more complex quantum systems.

Despite the progress, Pan said, the prospect of using it to beam people is still a distant dream. The technology is now mainly applied in the areas of quantum communication and computing.

But like most sci-fi fans, Pan hopes that day will come: "It's a common dream to see what's beyond our solar system. However, our life is limited, and we could grow old before we get out of the solar system in a spacecraft."

But as a vehicle to the stars, quantum teleportation might carry generations to come, Pan said.