First underwater entanglement could lead to unhackable comms

[cirr]

23 August 2017

First underwater entanglement could lead to unhackable comms

No eavesdropping with quantum comms Getty Images

By Devin Powell

The weird world of quantum mechanics is going for a swim. A team of Chinese researchers has, for the first time, transmitted quantum entangled particles of light through water – the first step in using lasers to send underwater messages that are impossible to intercept.

“People have talked about the idea of underwater quantum communication before, but I’m not aware of anyone who has done an experiment like this,” says Thomas Jennewein at the University of Waterloo in Canada. “An obvious application would be a submarine which wants to remain submerged but communicate in a secure fashion.”

Entanglement starts with a beam of light shot into a crystal. This prism splits the light into pairs of photons with strangely linked behaviour. Manipulate one particle in a pair, and its partner will instantly react. Measure the first one’s polarisation, for example, and entanglement could ensure that its twin will have the opposite polarisation when measured.

These entangled photons can theoretically be used to set up a secure communication line between two people, with privacy guaranteed by the laws of physics.

But this fragile quantum state can easily be disturbed by the surrounding environment. So far, entanglement has been maintained between particles separated by long distances after traveling through air, space and optical fibres.

To test entanglement in water, which is less forgiving toward light, Xianmin Jin and his colleagues at Shanghai Jiao Tong University in China gathered saltwater from the Yellow Sea and placed it in a 3-metre-long container. They were able to transmit entangled photons through the water without disturbing their quantum link.

As the first experiment of its kind, it’s not clear whether this will be enough to build a communications system. Three meters may not seem that impressive compared with the 1200 kilometres that a Chinese satellite recentlysent entangled particles down to Earth’s surface. “It’s not very surprising to me that if I send light through 10 feet of water it doesn’t get depolarised,” says Paul Kwiat at the University of Illinois at Urbana-Champaign.

But Jin says this is only the beginning. His team’s calculations suggest that it should be possible to communicate over nearly 900 metres in water. Previous calculations set a more conservative limit of just over 120 metres.

“Because ocean water absorbs light, extending this is going to difficult,” says Jeffrey Uhlmann at the University of Missouri in Columbia. “One option would be to use relays, but right now this is very far removed from anything that would be practical.”

https://www.newscientist.com/articl...-entanglement-could-lead-to-unhackable-comms/

http://www.dailymail.co.uk/sciencet...n-breakthrough-bring-unhackable-internet.html

 

[qwerrty]

china is on fire with this quantum shit

 

[cirr]

china is on fire with this quantum shit

Quantum communication test successful, good news for the Navy

2017-08-29 08:47

Global Times Editor: Li Yan

Technology able to securely communicate with satellites and aircraft

Chinese scientists successfully tested quantum communication under the surface of the sea, marking a global breakthrough in such technology.

The experiment was conducted by Jin Xianmin, and his team from Shanghai Jiao Tong University. In their experiment, the team was able to conduct communication secured by quantum mechanics between two underwater points several hundred meters apart, Jin told the Global Times on Monday, adding that the team was also able to securely communicate with satellites and aircraft from a point several meters under the sea.

Quantum communication is ultra-secure as a quantum photon can neither be separated nor duplicated. Accordingly, it is impossible to wiretap, intercept or crack information it transmits.

Once operationalized, such technology is expected to come in handy in the field of military, finance, and public information safety, according to Jin.

To carry out the experiment, the team collected samples of saltwater from six sites in the Yellow Sea, which they placed in containers, to see whether variations in the water affect their results, Jin said.

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 performance of the pair of particles is now linked, theoretically over any distance, allowing data to be transmitted between the two.

Jin said that although the floating matter and salt in the sea can result in the loss of photons, the research team found a window which can enable the photons to travel and hence preserve enough photons to securely communicate.

"Such windows can be spotted by commercial photon detectors," said Jin.

He noted that if the seawater, which covers more than 70 percent of the Earth, cannot be covered, the global quantum communication will remain incomplete.

"The quantum communication is highly secured and is free from interruptions, so solving the problem of underwater quantum communication is a good news for the Navy," Li Jie, a Beijing-based naval expert, told the Global Times on Monday.

However, according to Jin, the experiment is just the first step toward underwater quantum communication, and there is still a long way to go before a quantum communication network can be built incorporating both the sea and sky.

China has made several breakthroughs in the field of quantum communication in recent years.

Before Jin, a team from the University of Science and Technology of China led by Pan Jianwei, an academician with the Chinese Academy of Sciences, announced in July that they overcame the sunlight noise and demonstrated free-space quantum key distribution over 53 kilometers during the day.

China is striving to set up the first-ever global quantum communication network by around 2030, through linking a satellite constellation consisting of dozens of quantum satellites and ground-based quantum communication networks, according to the Xinhua News Agency.

http://www.ecns.cn/2017/08-29/271136.shtml