Quantum Cryptography System Breaks Daylight Distance Record

[cirr]

Quantum Cryptography System Breaks Daylight Distance Record

By Charles Q. Choi

Posted 24 Jul 2017 | 15:26 GMT

Quantum cryptography exploits the quantum properties of particles such as photons to help encrypt and decrypt messages in a theoretically unhackable way. Scientists worldwide are now endeavoring to develop satellite-based quantum communications networks for a global real-time quantum Internet.

However, prior experiments with long-distance quantum communications links through the air were mostly conducted at night because sunlight serves as a source of noise. Previously, “the maximum range for day-time free-space quantum communication was 10 kilometers,” says study co-senior author Qiang Zhang, a quantum physicist at the University of Science and Technology of China in Shanghai.

Now researchers led by quantum physicist Jian-Wei Pan at the University of Science and Technology of China at Hefei have successfully established 53-kilometer quantum cryptography links during the day between two ground stations. This research suggests that such links could work between a satellite and either a ground station or another satellite, they say.

To overcome interference from sunlight, the researchers switched from the roughly 700-to-900-nanometer wavelengths of light used in all prior day-time free-space experiments to roughly 1,550 nm. The sun is about one-fifth as bright at 1,550 nanometers as it is at 800 nanometers, and 1,550-nanometer light can also pass through Earth's atmosphere with virtually no interference. Moreover, this wavelength is also currently widely used in telecommunications, making it more compatible with existing networks.

Previous research was reluctant to use 1,550-nanometer light because of a lack of good commercial single-photon detectors capable of working at this wavelength. But the Shanghai group developed a compact single-photon detector for 1,550-nanometer light that could work at room temperature. Moreover, the scientists developed a receiver that needed less than one tenth of the field of view that receivers for night-time quantum communications links usually need to work. This limited the amount of noise from stray light by a factor of several hundred.

In experiments, the scientists repeatedly established quantum communications links across Qinghai Lake, the biggest lake in China, from 3:30 p.m. to 5 p.m. local time on several sunny days, achieving transmission rates of 20 to 400 bits per second. Furthermore, they could establish these links despite roughly 48 decibels of loss in their communications channel, which is more than the roughly 40 to 45 decibels of loss typically seen in communications channels between satellites and the ground and between low-Earth-orbit satellites, Zhang says. In comparison, previous day-time free-space quantum communications experiments could only accommodate roughly 20 decibels of noise.

The researchers note that their experiments were performed in good weather, and that quantum communication is currently not possible in bad weather with today’s technology. Still, they note that bad weather is only a problem for ground-to-space links, and that it would not pose a problem for links between satellites.

In the future, the researchers expect to boost transmission rates and distance using better single-photon detectors, perhaps superconducting ones. They may also seek to exploit the quantum phenomenon known as entanglementto carry out more sophisticated forms of quantum cryptography, although this will require generating very bright sources of entangled photons that can operate in a narrow band of wavelengths, Zhang says.

The scientists detailed their findings online 24 July in the journal Nature Photonics.

http://spectrum.ieee.org/tech-talk/...cryptography-in-daylight-across-53-kilometers

 

[cirr]

China set to launch an 'unhackable' internet communication

By Andreas Illmer

BBC News

25 July 2017

Image copyright SPL Quantum communication uses light to send crucial information

As malicious hackers mount ever more sophisticated attacks, China is about to launch a new, "unhackable" communications network - at least in the sense that any attack on it would be quickly detected.

The technology it has turned to is quantum cryptography, a radical break from the traditional encryption methods around. The Chinese project in the city of Jinan has been touted as a milestone by state media.

The pioneering project is also part of a bigger story: China is taking the lead in a technology in which the West has long been hesitant to invest.

In the Jinan network, some 200 users from the military, government, finance and electricity sectors will be able to send messages safe in the knowledge that only they are reading them.

China's push in quantum communication means the country is taking huge strides developing applications that might make the increasingly vulnerable internet more secure. Applications that other countries soon might find themselves buying from China.

So, what is this technology into which the country is pouring massive resources?

'Unhackable' communication

If you send a message you want to keep secure from eavesdroppers, traditional encryption works by hiding the key needed to read the message in a very difficult mathematical problem.

But what is "difficult" in terms of maths? It means you have to think really fast to figure it out as you try endless combinations of long, numeric keys. In 2017, that means you need to use a very powerful computer.

Steady improvements in computer power mean that the number-based keys have to be lengthened periodically. Encryption has a shelf life and is rapidly becoming more vulnerable.

There are also fears that the development of quantum computers, which effectively represent a massive step change in number crunching ability, will render much of modern encryption software vulnerable.

Quantum communication works differently:

• If you want to send your secure message, you first separately send a key embedded in particles of light
• Only then doyou send your encrypted message and the receiver will be able to read it with the help of the key sent beforehand
• 
  
• 
• Image copyrightSPL If a key is embedded in light particles, any interception will be noticed

The crucial advantage of this so-called quantum key distribution is that if anyone tries to intercept the light particles, they necessarily alter or destroy them.

What this means is that any attempt at hacking will immediately be noticed by the original sender and the intended receiver - hence its description as "unhackable".

Leaving the West behind

If quantum communication can help to secure online communications, why is China so far ahead?

"For a long time people simply didn't think it was needed," says Prof Myungshik Kim of Imperial College, London, adding that it was not clear whether there was a commercial market for this technology.

"The mathematical difficulty of the current coding system was so high that it was not thought necessary to implement the new technology," he says.

The research itself is not new and China does not have an edge over the competition. Where it does have an advantage is when it comes to applications.

"Europe has simply missed the boat," says Prof Anton Zeilinger, a quantum physicist at Vienna University in Austria and a pioneer in the field.

He says he tried to convince the EU as early as 2004 to fund more quantum-based projects but it had little effect.

"Europe has been dragging its feet and this has hindered us from being able to compete," he says.

There are quantum key-based networks operating in the US and Europe but most are being carried out as research projects, rather than with commercial partners.

Creating a market

One problem is that it is expensive to build applications like the Jinan network. And if there is not yet a commercial market, it is hard to get investors or governments as backers.

"We have to admit that when China invests into something, they have the financial power and manpower that is beyond probably anything else in the world except the US military," says Valerio Scarani, a physicist with Centre for Quantum Technologies at the National University of Singapore.

The Jinan network is not the only quantum communication application China has developed.

Image copyright CHINA DAILY/REUTERS China's quantum satellite was launched from the Gobi Desert

Last year, it launched a satellite equipped to test quantum communication over large distances that cannot be bridged by cables. There has also been a link established between the country's two main hubs, Beijing and Shanghai, so both ends can communicate and know when others are listening in.

So while it might not be clear yet whether quantum communication will indeed be the one technology to replace traditional encryption, it is widely considered as one of the leading candidates.

And China, in turn, is the leading country when it comes to building and experimenting with real applications of it.

"It's a situation where the technology can create its market," says Prof Zeilinger.

Once the technology is sold by Chinese companies, international banks might well be the first lining up as customers.

http://www.bbc.com/news/world-asia-40565722

 

[AndrewJin]

 

[cirr]

Chinese scientists vow to work on practicability of new QKD finding

2017-07-27 09:08

Global Times Editor: Li Yan

Having successfully demonstrated long-distance quantum key distribution (QKD) during daylight, Chinese scientists have vowed to continue their work to enhance its application including in satellites.

The long-distance free-space QKD could only be available during the night, "as the background noise during the daylight is typically five times greater than that during the night," prohibiting quantum communication in transmission under conditions of high channel loss over long distances, Peng Chengzhi, a senior scientist at the University of Science and Technology of China and a member of the research team, told the Global Times on Wednesday.

"Our experiment has proved the feasibility of satellite-based quantum communication in daylight, and laid a foundation for a satellite-constellation-based global quantum network," Pan Jianwei, an academician with the Chinese Academy of Sciences, who leads the research team, was quoted by the Xinhua News Agency on Tuesday as saying.

As a solution to overcome the background noise, the research team chose a wavelength of 1,550 nanometers and developed free-space single-mode fibre-coupling technology and ultra-low-noise upconversion single-photon detectors to achieve the daytime distribution.

The new technology was announced on Monday in the journal Nature Photonics.

China is now way ahead of the world in the field of quantum communication development, Peng said.

The research team will continue to work on improving the practicability of QKD, such launch of satellites at higher orbit and construction satellite constellation, Peng said.

And to increase the link efficiency, they need to develop new techniques including larger-size telescopes, better acquiring, pointing, and tracking systems, and wave-front correction through adaptive optics, which are on the agenda of the research team, according to Peng.

Peng also revealed the team's ultimate goal of "providing a global quantum network consisting of a quantum satellite constellation and existing ground fibre networks."

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

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.

http://www.ecns.cn/2017/07-27/266900.shtml

 

[oprih]

Congratulations to our Chinese brothers in this great achievement! Looks like another field where China is the leader.

 

[Jhon Smith]

Chinese scientists vow to work on practicability of new QKD finding


"Our experiment has proved the feasibility of satellite-based quantum communication in daylight, and laid a foundation for a satellite-constellation-based global quantum network," Pan Jianwei, an academician with the Chinese Academy of Sciences, who leads the research team, was quoted by the Xinhua News Agency on Tuesday as saying.http://www.ecns.cn/2017/07-27/266900.shtml

Hi man once you comment on my thread. So here I m, I appreciate you are fascinated by "quantum cryptography"Quantum cryptography technology is available in labs (where these researchers are doing experiment since 30 years), but there is much doubt as to whether it is actually used.

However I can explain you for ur understanding, This quantum entanglement physics is theoretical idea and many Physicist are trying to convert it into practical. That are not possible and those are doing such are lost in paths, as they could not understand the theoretical frame work of Quantum physics .
https://www.physicsforums.com/threads/why-is-quantum-mechanics-so-difficult-comments.765713/
I can simply say to u these so called quantum cryptography scientist are crap and lost. They even cant solve or understand simple mathematics behind quantum cryptography technology.

https://www.physicsforums.com/insights/quantum-mechanics-difficult/
Here are the pic of Quantum computer!! So imagine what raw deal is that.
Do you ever seen any quantum computer??? As there is nothing such thing do exist!!

https://cs.stanford.edu/people/eroberts/courses/soco/projects/2004-05/cryptography/quantum.html