Physicists in China have revealed the details on their ground-breaking experiment to achieve ‘ultra-long-distance quantum teleportation,’ which could pave the way for a global quantum internet.

In a major breakthrough, the team established the first ground-to-satellite quantum network, which allowed them to transmit a photon from an entangled pair up to 870 miles (1,400 kilometers).

Entangled photons theoretically maintain their link across any distance, and have potential to revolutionize secure communications – but, scientists have previously only managed to maintain the bond for about 62 miles (100 km).

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In a major breakthrough, the team established the first ground-to-satellite quantum network, which allowed them to transmit a photon from an entangled pair up to 870 miles (1,400 kilometers). An artist's impression of the Micius 'quantum' satellite is pictured

WHAT IS QUANTUM ENTANGLEMENT? In quantum physics, entangled particles remain connected so that actions performed by one affects the behaviour of the other, even if they are separated by huge distances. This means if you measure, 'up' for the spin of one photon from an entangled pair, the spin of the other, measured an instant later, will be 'down' - even if the two are on opposite sides of the world. Entanglement takes place when a part of particles interact physically. For instance, a laser beam fired through a certain type of crystal can cause individual light particles to be split into pairs of entangled photons. The theory that so riled Einstein is also referred to as 'spooky action at a distance'. Einstein wasn't happy with theory, because it suggested that information could travel faster than light. Advertisement

The experiments relied on the ‘quantum satellite’ Micius, which launched to a Sun-synchronous orbit last year from the Jiuquan Satellite Launch Centre.

As the satellite moves through its orbit, its distance from the Tibetan ground station varies from 500 km to 1400 km (310.7 – 869.9 miles).

‘In our experiment, the quantum state to be teleported is the polarization of a single photon,’ the researchers explain in the paper, published to arXiv.

‘Such a single qubit is generated from an observatory ground station in Ngari, and aimed to be teleported to the Micius satellite that has been launched from China on 16th August 2016 to an altitude of ~500 km.’

This setup is what’s known as an uplink configuration, according to the researchers.

The 1,300 pound craft satellite is equipped with a laser beam, which the scientists subjected to a beam splitter.

This gave the beam two distinct polarized states.

In the up-link approach, the transmitter is located at the ground station, while the satellite acts as the receiver.

As the satellite moves through its orbit, its distance from the Tibetan ground station varies from 500 km to 1400 km (310.7 – 869.9 miles). In the up-link approach, the transmitter is located at the ground station, while the satellite acts as the receiver, as illustrated

The graph shows the distance from the ground station to the orbiting satellite and the measured attenuation during one orbit. The trajectory of the Micuis satellite measured from Ngari ground station is shown (a), along with the measured ground-to-satellite channel loss

This technique, however, presented a number of challenges, which required the team to develop several workarounds.

‘To optimize the link efficiency and overcome the atmospheric turbulence in the up-link, a series of techniques are developed,’ the researchers explain, ‘including a compact ultra-bright source of multi-photon entanglement, narrow beam divergence, high-bandwidth and high-accuracy acquiring, pointing, and tracking (APT).’

Not only did the team successfully transmit single-photon qubits over hundreds of miles, from Earth to space, for the first time, but they managed to do it for six input states, to ‘demonstrate that the quantum teleportation is universal.’

The breakthrough now puts scientists a major step closer to developing an ultra-secure global internet.

In quantum physics, entangled particles remain connected so that actions performed by one affects the behaviour of the other, even if they are separated by huge distances. This is illustrated in the artist's impression above

HOW THEY DID IT Scientists in China have successfully transmitted entangled photons farther than ever before, achieving a distance of up to 1,400 kilometers (870 miles) between suborbital space and Earth. Using the ‘quantum satellite’ Micius, the scientists were able to to transmit a photon from an entangled pair from the ground station in Tibet to the orbiting craft, in what's known as an uplink configuration. The 1,300 pound craft satellite is equipped with a laser beam, which the scientists subjected to a beam splitter. This gave the beam two distinct polarized states. In the uplink approach, the transmitter is located at the ground station, while the satellite acts as the receiver. Not only did the team successfully transmit single-photon qubits over hundreds of miles for the first time, but they managed to do it for six input states, to ‘demonstrate that the quantum teleportation is universal.’ Advertisement

Pairs of entangled photons fired to ground stations can form a ‘secret key’ – and, theoretically, any attempts to breach this type of communication would be easily detectable.

According to the researchers, ‘This work establishes the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet.’

The Micius satellite launched from Jiuquan Satellite launch Center last year, and the new findings mark a promising step forward in the two-year mission prove successful, which could be followed by a fleet of others if all goes well, according to Nature.

To overcome the complications of long-distance quantum entanglement, scientists often break the line of transmission up, creating smaller segments that can then repeatedly swap, purify, and store the information along the optical fiber, according to the American Association for the Advancement of Science.

Or, as in this case, they can use lasers and satellites.

The researchers sought to prove that particles can remain entangled across great distances, aiming for nearly 750 miles.

Earlier efforts to demonstrate quantum communication have shown this can be done up to just over 180 miles, and scientists hope that transmitting the photons through space will push this even farther.

When travelling through air and optical fibres, protons get scattered or absorbed, Nature explains, posing challenges to the preservation of the fragile quantum state.

In a major breakthrough for quantum teleportation, scientists in China have successfully transmitted entangled photons farther than ever before, achieving a distance of more than 1,200 km (745 miles) between suborbital space and Earth

But, photons can travel more smoothly through space.

Achieving quantum communication at such distances would enable the creation of secure worldwide communications networks, allowing two parties to communicate using a shared encryption key.

In quantum physics, entangled particles remain connected so that actions performed by one affects the behaviour of the other, even if they are separated by huge distances.

So, if someone were to attempt to listen in on one end, the disruption would be detectable on the other.

Over the course of the two-year mission, the researchers in China will conduct a Bell test to prove the existence of entanglement at such a great distance.

And, they will attempt to ‘teleport’ quantum states, according to Nature, meaning the quantum state of the photo will be rebuilt in a new location.

Researchers from Canada, Japan, Italy, and Singapore have also revealed plans to conduct quantum experiments in space, including one proposed aboard the International Space Station.

This experiment would attempt to create a reliable and efficient means for teleportation.

By achieving quantum teleportation, the researchers say they could create a telescope with an enormous resolution.