- Entangled particles remain connected even if when separated by huge distances
- This allows data that is impervious to hackers to be ‘teleported’ between the two
- Satellites have been used over a distance of more than 745 miles (1,200 km)
- The underwater test took place across a more modest ten feet (three metres)
In a major breakthrough for quantum teleportation, scientists in China have successfully transmitted entangled photons underwater for the first time.
Sent down particles of light, they can theoretically maintain their link across any distance and have the potential to revolutionise secure communications.
Chinese scientists have used the technology in recent months to transmit information to satellites over a distance of more than 745 miles (1,200 km).
The latest technique is the first step in using lasers to send unhackable internet data across the world’s oceans.
In a major breakthrough for quantum teleportation, scientists in China have successfully transmitted entangled photons underwater for the first time. The technique is the first step in using lasers to send unhackable internet data across the world’s oceans
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.
Researchers from Shanghai Jiao Tong University in China proved the concept across a more modest distance of ten feet (three metres), than their satellite wielding peers.
They did so by collecting samples of saltwater from six sites in the Yellow Sea, which they placed in containers, to establish whether variations in the water affected their results.
A beam of light was then shot through a crystal, which split it into pairs of photons which are connected at the sub-atomic, or quantum, level.
This means that the behaviour of the pair of particles is now linked, theoretically over any distance, allowing data to be ‘teleported’ between the two.
However, this quantum link between can be easily disrupted by the surrounding environment, particularly water which absorbs light.
So far, it has been successfully demonstrated that quantum entanglement can survive transmission via fibre optic cables, the Earth’s atmosphere and the vacuum of space.
But the Chinese team’s work suggests that quantum teleportation may also work underwater, with data transmitted using the process retaining 98 per cent fidelity.
Transmitting data via existing underwater methods is faster and cheaper than using satellites.
Writing in the paper, its authors said: ‘Long-distance quantum channels capable of transferring quantum states faithfully for unconditionally secure quantum communication have been so far confirmed to be feasible in both fibre and free-space air.
‘However, it remains unclear whether seawater, which covers more than 70 per cent of the Earth, can also be utilised, leaving global quantum communication incomplete.
‘Here we experimentally demonstrate that polarisation quantum states including general qubits of single photon and entangled states can survive well after travelling through seawater.’
The three metres achieved by the Jiao Tong team is not enough to build a long-distance communications array.
A beam of light was shot through a crystal (top left), which split it into pairs of photons which are connected at the sub-atomic level. This means that the behaviour of the pair of particles is now linked, theoretically over any distance, allowing data to be ‘teleported’ between the two
Data transmitted over a distance of ten feet (three metres) using the process retained 98 per cent fidelity (pictured)
But the proof of concept suggests that it could be used to transmit information over approximately 3,000 feet (900 metres), according to reports in New Scientist.
Previous estimates have placed a limit of around 400 feet (120 metres).
If the higher limit is proven correct, it could allow for a system to forward information accurately over longer distances.
The full results of the study were published in the journal Optics Express.
Chinese scientists proved the viability of quantum communications between the Earth and satellites back in June.
Using the quantum satellite Micius, they were able to communicate with three ground stations in China, each more than 621 miles (1,000 km) apart.
Entangled particles (artist’s impression) remain connected even if they are separated by huge distances, allowing data to be ‘teleported’ between the two
Their experiment was tested on seawater taken from 22 mile stretch of water between Dalian City on China’s coast and offshore Zhangzi Island (pictured)
Researchers collected samples of saltwater from six sites in the Yellow Sea (pictured), to establish whether variations in the water affected their results
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.
Using the ‘quantum satellite’ Micius, the scientists were able to communicate with three ground stations in China, each more than 1,000 km (621 miles) apart.
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.
One of these beams was then used to transmit entangled particles, and the other used to receive the photons.
The 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 – in this case, 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.