China Quantum Communiations Technology: Cryptography, Radar, Satellite, Teleportation, Network

[cirr]

Scientists Achieve Direct Counterfactual Quantum Communication For The First Time

1 day ago

IN BRIEF

For the first time in the history of quantum mechanics, scientists have been able to transmit a black and white image without having to send any physical particles. The phenomenon can be explained using the Zeno effect, the same effect that explains that movement itself is impossible.

COUNTERFACTUAL COMMUNICATION

Quantum communication is a strange beast, but one of the weirdest proposed forms of
it is called counterfactual communication – a type of quantum communication where no particles travel between two recipients.

Theoretical physicists have long proposed that such a form of communication would be possible, but now, for the first time, researchers have been able to experimentally achieve it – transferring a black and white bitmap image from one location to another without sending any physical particles.

If that sounds a little too out-there for you, don’t worry, this is quantum mechanics, after all. It’s meant to be complicated. But once you break it down, counterfactual quantum communication actually isn’t as bizarre as it sounds.

First up, let’s talk about how this differs from regular quantum communication, also known as quantum teleportation because isn’t that also a form of particle-less information transfer?

Well, not quite. Regular quantum teleportation is based on the principle ofentanglement – two particles that become inextricably linked so that whatever happens to one will automatically affect the other, no matter how far apart they are.

This is what Einstein referred to as “spooky action at a distance“, and scientists have already used it to send messages over vast distances.

But that form of quantum teleportation still relies on particle transmission in some form or another. The two particles usually need to be together when they’re entangled before being sent to the people on either end of the message (so, they start in one place, and need to be transmitted to another before communication can occur between them).

ENTER ZENO

Alternatively, particles can be entangled at a distance, but it usually requiresanother particle, such as photons (particles of light), to travel between the two.

Direct counterfactual quantum communication, on the other hand, relies on something other than quantum entanglement. Instead, it uses a phenomenon called the quantum Zeno effect.

Very simply, the quantum Zeno effect occurs when an unstable quantum system is repeatedly measured.

In the quantum world, whenever you look at a system, or measure it, the system changes. And in this case, unstable particles can never decay while they’re being measured (just like the proverbial watched kettle that will never boil), so the quantum Zeno effect creates a system that’s effectively frozen with a very high probability.

If you want to delve a little deeper, the video below gives a great explanation:

https://futurism.com/scientists-ach...ual-quantum-communication-for-the-first-time/

Counterfactual quantum communication is based on this quantum Zeno effect, and is defined as the transfer of a quantum state from one site to another without any quantum or classical particle being transmitted between them.

This requires a quantum channel to run between two sites, which means there’s always a small probability that a quantum particle will cross the channel. If that happens, the system is discarded and a new one is set up.

To set up such a complex system, researchers from the University of Science and Technology of China placed two single-photon detectors in the output ports of the last of an array of beam splitters.

Because of the quantum Zeno effect, the system is frozen in a certain state, so it’s possible to predict which of the detectors would ‘click’ whenever photons passed through. A series of nested interferometers measure the state of the system to make sure it doesn’t change.

It works based on the fact that, in the quantum world, all light particles can be fully described by wave functions, rather than as particles. So by embedding messages in light the researchers were able to transmit this message without ever directly sending a particle.

THE ANSWER IN LIGHT

The team explains that the basic idea for this set up came from holography technology.

“In the 1940s, a new imaging technique – holography – was developed to record not only light intensity but also the phase of light,” the researchers write in the journal Proceedings of the National Academy of Sciences.

“One may then pose the question: Can the phase of light itself be used for imaging? The answer is yes.”

The basic idea is this – someone wants to send an image to Alice using only light (which acts as a wave, not a particle, in the quantum realm).

Alice transfers a single photon to the nested interferometer, where it can be detected by three single-photon detectors: D0, D1, and Df.

If D0 or D1 ‘click’, Alice can conclude a logic result of one or zero. If Df clicks, the result is considered inconclusive.

As Christopher Packham explains for Phys.org:

“After the communication of all bits, the researchers were able to reassemble the image – a monochrome bitmap of a Chinese knot. Black pixels were defined as logic 0, while white pixels were defined as logic 1 …

In the experiment, the phase of light itself became the carrier of information, and the intensity of the light was irrelevant to the experiment.”

Not only is this a big step forward for quantum communication, the team explains it’s technology that could also be used for imaging sensitive ancient artefacts that couldn’t surprise direct light shined on them.

The results will now need to be verified by external researchers to make sure what the researchers saw was a true example of counterfactual quantum communication.

Either way, it’s a pretty cool demonstration of just how bizarre and unexplored the quantum world is.

The research has been published in the journal Proceedings of the National Academy of Sciences.

https://futurism.com/scientists-ach...ual-quantum-communication-for-the-first-time/

 

[cirr]

Quantum Domain Breakthrough: For The First Time, Scientists Demonstrate Counterfactual Communication

Communicating without the use of particles to transmit information is no longer just a theory.

May 14, 2017 WSP

Counterfactual communication is a kind of quantum communication where no particles travel between recipients to transmit information. For the first time ever, a team of Chinese scientists has successfully demonstrated, at least experimentally, that this type of communication is possible. Specifically, the team was able to transfer a monochromatic bitmap image from one location to another without making use of any physical particle to achieve the transfer. And they did it by applying the quantum Zeno effect.

Don’t worry if you got lost in those statements somewhere. We’re delving into the quantum world, after all. And in there, nothing is really simple. In fact, everything about it is like straight out of science fiction. So just brace yourself for more quantum weirdnesss.

The quantum Zeno effect is something that happens when an unstable quantum system is measured over and over. As it is, when you observe or measure a system in the quantum world, the system changes. Following this principle, unstable particles in the quantum world can never decay as they are being measured, meaning, the quantum Zeno effect creates a system that is effectively frozen.

Applying this effect, the research team designed a set-up consisting of two single-photon detectors placed in the output ports of an array of beam splitters, with nested interferometers measuring the system to ensure it doesn’t change. In theory, because of the quantum Zeno effect, it should be possible to predict which of the single-photon detectors will click when photons are allowed to pass through. This also incorporates the idea that counterfactuality requires a quantum channel between sites, and if a quantum particle happens to cross that channel, the system will have to be reset.

The experiment, as described in Phys.org, went as follows: ‘Alice transfers a single photon to the nested interferometer; it is detected by three single photon detectors, D0, D1 and Df. If D0 or D1 click, Alice concludes a logic result of one or zero. If Df clicks, the result is considered inconclusive, and is discarded in post-processing.’

When the communication of all bits was done following the given process, with logic 0 corresponding to black pixels and logic 1 corresponding to white pixels, the team was able to recreate the image being transferred — a black and white bitmap of a Chinese knot.

The idea for the experiment stemmed from the imaging technique known as holography which was developed to record both the phase of light and its intensity. The scientists wanted this question answered: can the phase of light be used for imaging? Based on the result of their experiment, the answer is yes — the phase of light became the carrier of information.

According to the team, aside from applications in quantum communication, their technique could also be used for activities such as ‘imaging ancient artifacts that would be damaged by directly shining light’ because as their experiment showed, only the phase of light mattered; its intensity was irrelevant.

The research was recently published in the journal Proceedings of the National Academy of Sciences.

http://wallstreetpit.com/113449-qua...sts-demonstrate-counterfactual-communication/

@Bussard Ramjet

 

[Shotgunner51]

Quantum Domain Breakthrough: For The First Time, Scientists Demonstrate Counterfactual Communication

Good job!

 

[onebyone]

By Roland PeaseBBC Radio Science Unit

• 3 hours ago
  
• From the sectionScience & Environment

Image copyrightGETTY IMAGES
Image captionMicius went up from the Jiuquan Satellite Launch Centre in China's north west
The term "spy satellite" has taken on a new meaning with the successful test of a novel Chinese spacecraft.

The mission can provide unbreakable secret communications channels, in principle, using the laws of quantum science.

Called Micius, the satellite is the first of its kind and was launched from the Gobi desert last August.

It is all part of a push towards a new kind of internet that would be far more secure than the one we use now.

The experimental Micius, with its delicate optical equipment, continues to circle the Earth, transmitting to two mountain-top Earth bases separated by 1,200km.

The optics onboard are paramount. They're needed to distribute to the ground stations the particles, or photons, of light that can encode the "keys" to secret messages.

"I think we have started a worldwide quantum space race," says lead researcher Jian-Wei Pan, who is based in Hefei in China's Anhui Province.

'Messy business'
Quantum privacy in many ways should be like the encryption that already keeps our financial data private online.

Before sensitive information is shared between shopper and online shop, the two exchange a complicated number that is then used to scramble the subsequent characters. It also hides the key that will allow the shop to unscramble the text securely.

The weakness is that the number itself can be intercepted, and with enough computing power, cracked.

Quantum cryptography, as it is called, goes one step further, by using the power of quantum science to hide the key.

As one of the founders of quantum mechanics Werner Heisenberg realised over 90 years ago, any measurement or detection of a quantum system, such as an atom or photon of light, uncontrollably and unpredictably changes the system.

This quantum uncertainty is the property that allows those engaged in secret communications to know if they are being spied on: the eavesdropper's efforts would mess up the connection.

Image copyrightNSSC
Image captionArtwork: The two Earth stations are 1,200km apart

The idea has been developed since it was first understood in the 1980s.

Typically, pairs of photons created or born simultaneously like quantum twins will share their quantum properties no matter how long they are separated or how far they have travelled. Reading the photons later, by shopper and shop, leads to the numerical key that can then be used to encrypt a message. Unless the measurements show interference from an eavesdropper.

A network established in Vienna in 2008 successfully used telecommunications fibre optics criss-crossing the city to carry these "entangled photons", as they are called. But even the clearest of optical fibres looks foggy to light, if it's long enough. And an ambitious 2,000km link from Beijing to Shanghai launched last year needs repeater hubs every 100km or so - weak points for quantum hackers of the future to target.

And that, explains Anton Zeilinger, one of the pioneers of the field and creator of the Vienna network, is the reason to communicate via satellite instead.

"On the ground, through the air, through glass fibres - you cannot go much further than 200km. So a satellite in outer space is the choice if you want to go a really large distance," he said.

The point being that in the vacuum of space, there are no atoms, or at least hardly any, to mess up the quantum signal.

That is what makes the tests with Micius, named after an ancient Chinese philosopher, so significant. They have proved a spaced-based network is possible, as revealed in the latest edition of the journal Science.

Technical tour de force
Not that it is easy. The satellite passes 500km over China for just less than five minutes each day - or rather each night, as bright sunlight would easily swamp the quantum signal. Micius' intricate optics create the all-important photon pairs and fires them down towards telescopes on some of China's high mountains.

"When I had the idea of doing this in 2003, many people thought it was a crazy idea," Jian-Wei Pan told the BBC World Service from his office in the University of Science and Technology of China. "Because it was very challenging already doing the sophisticated quantum optics experiments in a lab - so how can you do a similar experiment at a thousand-kilometre distance and with optical elements moving at a speed of 8km/s?"

Additional lasers steered the satellite's optics as it flew over China, keeping them pointed at the base stations. Nevertheless, owing to clouds, dust and atmospheric turbulence, most of the photons created on the satellite failed to reach their target: only one pair of the 10 million photon pairs generated each second actually completed the trip successfully.

But that was enough to complete the test successfully. It showed that the photons that did arrive preserved the quantum properties needed for quantum crypto-circuits.

"The Chinese experiment is a quite remarkable technological achievement," enthused mathematician Artur Ekert in an e-mail to the BBC. It was as a student in quantum information at Oxford University in the 1990s that Ekert proposed the paired-photon approach to cryptography. Relishing the pun, he added wryly "when I proposed the scheme, I did not expect it to be elevated to such heights."

Alex Ling from the National University of Singapore is a rival physicist. His first quantum minisatellite blew up shortly after launch in 2014, but he is generous in his praise of the Micius mission: "The experiment is definitely a technical tour de force.

"We are pretty excited about this development, and hope it heralds a new era in quantum communications capability."

Image copyrightSPL
Image captionJian-Wei Pan is now set to team up with his old PhD supervisor, Anton Zeilinger, who is based in Vienna
The next step will be a collaboration between Jian-Wei Pan and his former PhD supervisor, Anton Zeilinger in the University of Vienna - to prove what can be done across a single nation can also be achieved between whole continents, still using Micius.

"The idea is the satellite flies over China, establishes a secret key with a ground station; then it flies over Austria, it establishes another secret key with that ground station. Then the keys

are combined to establish a key between say Vienna and Beijing," he told the BBC's Science in Action programme.
Pan says his team will soon arrive in Vienna to start those tests.

Meanwhile, Zeilinger is working on Qapital, a quantum network connecting many of the capitals of Europe, Vienna and Bratislava. Existing optic fibres laid alongside data networks but not currently used could make the backbone of this network, Zeilinger believes.

"A future quantum internet," he says, "will consist of fibre optic networks on the ground that will be connected to other fibre networks by satellites overhead. I think it will happen."

Pan is already planning the details of the satellite constellation that will make this possible.

The need? Secrecy is the stuff of spy agencies, who have large budgets. But financial institutions which trade billions of dollars internationally day by day also have valuable resources to protect.

Although some observers are sceptical they would want to pay for a quantum internet, Pan, Zeilinger and the other technologists think the case will be irresistible once one exists.

http://www.bbc.com/news/science-environment-40294795

 

[onebyone]

• 1

China's quantum satellite achieves 'spooky action' at record distance
By Gabriel PopkinJun. 15, 2017 , 2:00 PM

Quantum entanglement—physics at its strangest—has moved out of this world and into space. In a study that shows China's growing mastery of both the quantum world and space science, a team of physicists reports that it sent eerily intertwined quantum particles from a satellite to ground stations separated by 1200 kilometers, smashing the previous world record. The result is a stepping stone to ultrasecure communication networks and, eventually, a space-based quantum internet.

"It's a huge, major achievement," says Thomas Jennewein, a physicist at the University of Waterloo in Canada. "They started with this bold idea and managed to do it."

Entanglement involves putting objects in the peculiar limbo of quantum superposition, in which an object's quantum properties occupy multiple states at once: like Schrödinger's cat, dead and alive at the same time. Then those quantum states are shared among multiple objects. Physicists have entangled particles such as electrons and photons, as well as larger objects such as superconducting electric circuits.
Theoretically, even if entangled objects are separated, their precarious quantum states should remain linked until one of them is measured or disturbed. That measurement instantly determines the state of the other object, no matter how far away. The idea is so counterintuitive that Albert Einstein mocked it as "spooky action at a distance."

Starting in the 1970s, however, physicists began testing the effect over increasing distances. In 2015, the most sophisticated of these tests, which involved measuring entangled electrons 1.3 kilometers apart, showed once again that spooky action is real.

Beyond the fundamental result, such experiments also point to the possibility of hack-proof communications. Long strings of entangled photons, shared between distant locations, can be "quantum keys" that secure communications. Anyone trying to eavesdrop on a quantum-encrypted message would disrupt the shared key, alerting everyone to a compromised channel.

But entangled photons degrade rapidly as they pass through the air or optical fibers. So far, the farthest anyone has sent a quantum key is a few hundred kilometers. "Quantum repeaters" that rebroadcast quantum information could extend a network's reach, but they aren't yet mature. Many physicists have dreamed instead of using satellites to send quantum information through the near-vacuum of space. "Once you have satellites distributing your quantum signals throughout the globe, you've done it," says Verónica Fernández Mármol, a physicist at the Spanish National Research Council in Madrid. "You've leapfrogged all the problems you have with losses in fibers."

CREDITS: (GRAPHIC) C. BICKEL/SCIENCE; (DATA) JIAN-WEI PAN
Jian-Wei Pan, a physicist at the University of Science and Technology of China in Shanghai, got the chance to test the idea when the Micius satellite, named after an ancient Chinese philosopher, was launched in August 2016. The satellite is the foundation of the $100 million Quantum Experiments at Space Scale program, one of several missions that China hopes will make it a space science power on par with the United States and Europe.

In their first experiment, the team sent a laser beam into a light-altering crystal on the satellite. The crystal emitted pairs of photons entangled so that their polarization states would be opposite when one was measured. The pairs were split, with photons sent to separate receiving stations in Delingha and Lijiang, 1200 kilometers apart. Both stations are in the mountains of Tibet, reducing the amount of air the fragile photons had to traverse. This week in Science, the team reports simultaneously measuring more than 1000 photon pairs. They found the photons had opposite polarizations far more often than would be expected by chance, thus confirming spooky action over a record distance (though the 2015 test over a shorter distance was more stringent).

The team had to overcome many hurdles, including keeping the beams of photons focused on the ground stations as the satellite hurtled through space at nearly 8 kilometers per second. "Showing and demonstrating it is quite a challenging task," says Alexander Ling, a physicist at the National University of Singapore. "It's very encouraging." However, Ling notes that Pan's team recovered only about one photon out of every 6 million sent from the satellite—far better than ground-based experiments but still far too few for practical quantum communication.

Pan expects China's National Space Science Center to launch additional satellites with stronger and cleaner beams that could be detected even when the sun is shining. (Micius operates only at night.) "In the next 5 years we plan to launch some really practical quantum satellites," he says. In the meantime, he plans to use Micius to distribute quantum keys to Chinese ground stations, which will require longer strings of photons and additional steps. Then he wants to demonstrate intercontinental quantum key distribution between stations in China and Austria, which will require holding one half of an entangled photon pair on board until the Austrian ground station appears within view of the satellite. He also plans to teleport a quantum state—a technique for transferring quantum-encoded information without moving an actual object—from a third Tibetan observatory to the satellite.

Other countries are inching toward quantum space experiments of their own. Ling is teaming up with physicists in Australia to send quantum information between two satellites, and the Canadian Space Agency recently announced funding for a small quantum satellite. European and U.S. teams are also proposing putting quantum instruments on the International Space Station. One goal is to test whether entanglement is affected by a changing gravitational field, by comparing a photon that stays in the weaker gravitational environment of orbit with an entangled partner sent to Earth, says Anton Zeilinger, a physicist at the Austrian Academy of Sciences in Vienna. "There are not many experiments which test links between gravity and quantum physics."

The implications go beyond record-setting demonstrations: A network of satellites could someday connect the quantum computers being designed in labs worldwide. Pan's paper "shows that China is making the right decisions," says Zeilinger, who has pushed the European Space Agency to launch its own quantum satellite. "I'm personally convinced that the internet of the future will be based on these quantum principles."

Posted in:

• Physics
• Space

DOI: 10.1126/science.aan6972

http://www.sciencemag.org/news/2017...ellite-achieves-spooky-action-record-distance

 

[bobsm]

China Shatters “Spooky Action at a Distance” Record, Preps for Quantum Internet

Results from the Micius satellite test quantum entanglement, pointing the way toward hack-proof global communications—and a new space race

By Lee Billings on June 15, 2017

In a landmark study, a team of Chinese scientists using an experimental satellite has tested quantum entanglement over unprecedented distances, beaming entangled pairs of photons to three ground stations across China—each separated by more than 1,200 kilometers. The test verifies a mysterious and long-held tenet of quantum theory, and firmly establishes China as the front-runner in a burgeoning “quantum space race” to create a secure, quantum-based global communications network—that is, a potentially unhackable “quantum internet” that would be of immense geopolitical importance. The findings were published Thursday in Science.

“China has taken the leadership in quantum communication,” says Nicolas Gisin, a physicist at the University of Geneva who was not involved in the study. “This demonstrates that global quantum communication is possible and will be achieved in the near future.”

The concept of quantum communications is considered the gold standard for security, in part because any compromising surveillance leaves its imprint on the transmission. Conventional encrypted messages require secret keys to decrypt, but those keys are vulnerable to eavesdropping as they are sent out into the ether. In quantum communications, however, these keys can be encoded in various quantum states of entangled photons—such as their polarization—and these states will be unavoidably altered if a message is intercepted by eavesdroppers. Ground-based quantum communications typically send entangled photon pairs via fiber-optic cables or open air. But collisions with ordinary atoms along the way disrupt the photons’ delicate quantum states, limiting transmission distances to a few hundred kilometers. Sophisticated devices called “quantum repeaters”—equipped with “quantum memory” modules—could in principle be daisy-chained together to receive, store and retransmit the quantum keys across longer distances, but this task is so complex and difficult that such systems remain largely theoretical.

more@ https://www.scientificamerican.com/...ance-rdquo-record-preps-for-quantum-internet/

 

[Pangu]

China's quantum satellite clears major hurdle on way to ultrasecure communications


Probe sends entangled photons — which could underpin quantum-based data encryption — over unprecedented distance.

• Davide Castelvecchi

15 June 2017
Article tools
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Jin Liwang/Xinhua via ZUMA Wire

A composite photo from December 2016 shows a link established between China's quantum satellite Micius and a ground station in the Tibet Autonomous Region.

Just months into its mission, the world’s first quantum-communications satellite has achieved one of its most ambitious goals.

Researchers report in Science1 that, by beaming photons between the satellite and two distant ground stations, they have shown that photons can remain in a linked quantum state at a record-breaking distance of more than 1,200 kilometres. That phenomenon, known as quantum entanglement, could be used as the basis of a future secure quantum-communications network.

The feat is the first result reported from China’s Quantum Experiments at Space Scale (QUESS) mission, also known as Micius after an ancient Chinese philosopher. Launched last August, the craft is designed to demonstrate principles underlying quantum communication. The team is likely to launch more quantum-enabled satellites to start building a network.

Quantum communication is secure because any interference is detectable. Two parties can exchange secret messages by sharing an encryption key encoded in the properties of entangled particles; any eavesdropper would affect the entanglement and so be detected.

The Micius team has already done experiments exploring whether it is possible to create such encryption keys using entangled photons, and even 'teleport' information securely between Earth and space, says Pan Jian-Wei, a physicist at the University of Science and Technology of China in Hefei and the main architect of the probe. But he says that his team is not yet ready to announce the results.

Bell test
In theory, entangled particles should remain linked at any separation. That can be checked using a classic experiment called a Bell test.

Central to QUESS's experiments is a laser beam mounted on the satellite. For the Bell test, the beam was split to generate pairs of photons that share a common quantum state, in this case related to polarization. The entangled photons were funnelled into two onboard telescopes that fired them at separate stations on the ground: one in Delingha, on the northern Tibetan Plateau, and the other 1,203 kilometres south, at Gaomeigu Observatory in Lijiang. Once the particles arrived, the team used the Bell test to confirm that they were still entangled.

The researchers had a window of less than 5 minutes each night when the satellite, which orbits at an altitude of about 500 kilometres, was in view of both observatories. Within weeks of launch, they were able to transmit a pair of entangled photons per second — a rate ten times faster than they had hoped. The crucial experiment was completed before the end of the year, says Pan: “We are very happy that the whole system worked properly.” The previous record for such an experiment was 144 kilometres2.

“This proves that one can perform quantum communications at continental distances,” says Frédéric Grosshans, a quantum-communications physicist at the University of Paris South in Orsay. Entangled particles are the “workhorse” of quantum communications, he adds.

China launched the world's first quantum-enabled satellite in August 2016.

Jin Liwang/Xinhua via ZUMA Wire

Next-generation satellite
“I am really impressed by the result of the Chinese group,” says Wolfgang Tittel, a physicist at the University of Calgary in Canada. “To me, it was not clear after the satellite launch if they would succeed,” he says, or whether they would use it to learn for the next improved mission.

Pan says that in addition to the quantum-key and teleportation experiments, the team also plans to use Micius to test how gravity affects the quantum state of photons. And they want to launch a second, improved, quantum satellite in two years. A major challenge, he says, will be to upgrade the technology so that it can send and receive signals during the day, when there are many more photons around and it is harder to pick out the ones coming from the satellite.

For now, Pan feels vindicated about the first spacecraft’s design. Colleagues thought that it was too ambitious, he says, because it produced the entangled photons in space and required two photon-firing systems.

Similar missions in the planning stages — such as Canada’s Quantum Encryption and Science Satellite (QEYSSat) — use a simpler approach, creating the entangled photons on Earth and beaming them to a satellite. In a study3 published last week, the QEYSSat team reported a successful test of its technology, transmitting photons from the ground to an aircraft as much as 10 kilometres in the air.

Thomas Jennewein, who is at the University of Waterloo in Canada and part of the Candanian mission, says that his group and others around the world are now racing to catch up with the Chinese effort. “They are now clearly the world leader in quantum satellites,” he says.

Nature

doi:10.1038/nature.2017.22142

Link: https://www.nature.com/news/china-s...-on-way-to-ultrasecure-communications-1.22142

 

[Han Patriot]

China's quantum satellite clears major hurdle on way to ultrasecure communications


Probe sends entangled photons — which could underpin quantum-based data encryption — over unprecedented distance.

• Davide Castelvecchi

15 June 2017
Article tools
Rights & Permissions

Jin Liwang/Xinhua via ZUMA Wire

A composite photo from December 2016 shows a link established between China's quantum satellite Micius and a ground station in the Tibet Autonomous Region.

Just months into its mission, the world’s first quantum-communications satellite has achieved one of its most ambitious goals.

Researchers report in Science1 that, by beaming photons between the satellite and two distant ground stations, they have shown that photons can remain in a linked quantum state at a record-breaking distance of more than 1,200 kilometres. That phenomenon, known as quantum entanglement, could be used as the basis of a future secure quantum-communications network.

The feat is the first result reported from China’s Quantum Experiments at Space Scale (QUESS) mission, also known as Micius after an ancient Chinese philosopher. Launched last August, the craft is designed to demonstrate principles underlying quantum communication. The team is likely to launch more quantum-enabled satellites to start building a network.

Quantum communication is secure because any interference is detectable. Two parties can exchange secret messages by sharing an encryption key encoded in the properties of entangled particles; any eavesdropper would affect the entanglement and so be detected.

The Micius team has already done experiments exploring whether it is possible to create such encryption keys using entangled photons, and even 'teleport' information securely between Earth and space, says Pan Jian-Wei, a physicist at the University of Science and Technology of China in Hefei and the main architect of the probe. But he says that his team is not yet ready to announce the results.

Bell test
In theory, entangled particles should remain linked at any separation. That can be checked using a classic experiment called a Bell test.

Central to QUESS's experiments is a laser beam mounted on the satellite. For the Bell test, the beam was split to generate pairs of photons that share a common quantum state, in this case related to polarization. The entangled photons were funnelled into two onboard telescopes that fired them at separate stations on the ground: one in Delingha, on the northern Tibetan Plateau, and the other 1,203 kilometres south, at Gaomeigu Observatory in Lijiang. Once the particles arrived, the team used the Bell test to confirm that they were still entangled.

The researchers had a window of less than 5 minutes each night when the satellite, which orbits at an altitude of about 500 kilometres, was in view of both observatories. Within weeks of launch, they were able to transmit a pair of entangled photons per second — a rate ten times faster than they had hoped. The crucial experiment was completed before the end of the year, says Pan: “We are very happy that the whole system worked properly.” The previous record for such an experiment was 144 kilometres2.

“This proves that one can perform quantum communications at continental distances,” says Frédéric Grosshans, a quantum-communications physicist at the University of Paris South in Orsay. Entangled particles are the “workhorse” of quantum communications, he adds.

China launched the world's first quantum-enabled satellite in August 2016.

Jin Liwang/Xinhua via ZUMA Wire

Next-generation satellite
“I am really impressed by the result of the Chinese group,” says Wolfgang Tittel, a physicist at the University of Calgary in Canada. “To me, it was not clear after the satellite launch if they would succeed,” he says, or whether they would use it to learn for the next improved mission.

Pan says that in addition to the quantum-key and teleportation experiments, the team also plans to use Micius to test how gravity affects the quantum state of photons. And they want to launch a second, improved, quantum satellite in two years. A major challenge, he says, will be to upgrade the technology so that it can send and receive signals during the day, when there are many more photons around and it is harder to pick out the ones coming from the satellite.

For now, Pan feels vindicated about the first spacecraft’s design. Colleagues thought that it was too ambitious, he says, because it produced the entangled photons in space and required two photon-firing systems.

Similar missions in the planning stages — such as Canada’s Quantum Encryption and Science Satellite (QEYSSat) — use a simpler approach, creating the entangled photons on Earth and beaming them to a satellite. In a study3 published last week, the QEYSSat team reported a successful test of its technology, transmitting photons from the ground to an aircraft as much as 10 kilometres in the air.

Thomas Jennewein, who is at the University of Waterloo in Canada and part of the Candanian mission, says that his group and others around the world are now racing to catch up with the Chinese effort. “They are now clearly the world leader in quantum satellites,” he says.

Nature

doi:10.1038/nature.2017.22142

Link: https://www.nature.com/news/china-s...-on-way-to-ultrasecure-communications-1.22142

Pan could be the next Nobel prize winner.

 

[JSCh]

China's quantum satellite achieves 'spooky action' at record distance
By Gabriel Popkin
Jun. 15, 2017 , 2:00 PM

Quantum entanglement—physics at its strangest—has moved out of this world and into space. In a study that shows China's growing mastery of both the quantum world and space science, a team of physicists reports that it sent eerily intertwined quantum particles from a satellite to ground stations separated by 1200 kilometers, smashing the previous world record. The result is a stepping stone to ultrasecure communication networks and, eventually, a space-based quantum internet.

"It's a huge, major achievement," says Thomas Jennewein, a physicist at the University of Waterloo in Canada. "They started with this bold idea and managed to do it."

Entanglement involves putting objects in the peculiar limbo of quantum superposition, in which an object's quantum properties occupy multiple states at once: like Schrödinger's cat, dead and alive at the same time. Then those quantum states are shared among multiple objects. Physicists have entangled particles such as electrons and photons, as well as larger objects such as superconducting electric circuits.

Theoretically, even if entangled objects are separated, their precarious quantum states should remain linked until one of them is measured or disturbed. That measurement instantly determines the state of the other object, no matter how far away. The idea is so counterintuitive that Albert Einstein mocked it as "spooky action at a distance."

Starting in the 1970s, however, physicists began testing the effect over increasing distances. In 2015, the most sophisticated of these tests, which involved measuring entangled electrons 1.3 kilometers apart, showed once again that spooky action is real.

Beyond the fundamental result, such experiments also point to the possibility of hack-proof communications. Long strings of entangled photons, shared between distant locations, can be "quantum keys" that secure communications. Anyone trying to eavesdrop on a quantum-encrypted message would disrupt the shared key, alerting everyone to a compromised channel.

But entangled photons degrade rapidly as they pass through the air or optical fibers. So far, the farthest anyone has sent a quantum key is a few hundred kilometers. "Quantum repeaters" that rebroadcast quantum information could extend a network's reach, but they aren't yet mature. Many physicists have dreamed instead of using satellites to send quantum information through the near-vacuum of space. "Once you have satellites distributing your quantum signals throughout the globe, you've done it," says Verónica Fernández Mármol, a physicist at the Spanish National Research Council in Madrid. "You've leapfrogged all the problems you have with losses in fibers."

CREDITS: (GRAPHIC) C. BICKEL/SCIENCE; (DATA) JIAN-WEI PAN​

Jian-Wei Pan, a physicist at the University of Science and Technology of China in Shanghai, got the chance to test the idea when the Micius satellite, named after an ancient Chinese philosopher, was launched in August 2016. The satellite is the foundation of the $100 million Quantum Experiments at Space Scale program, one of several missions that China hopes will make it a space science power on par with the United States and Europe.

In their first experiment, the team sent a laser beam into a light-altering crystal on the satellite. The crystal emitted pairs of photons entangled so that their polarization states would be opposite when one was measured. The pairs were split, with photons sent to separate receiving stations in Delingha and Lijiang, 1200 kilometers apart. Both stations are in the mountains of Tibet, reducing the amount of air the fragile photons had to traverse. This week in Science, the team reports simultaneously measuring more than 1000 photon pairs. They found the photons had opposite polarizations far more often than would be expected by chance, thus confirming spooky action over a record distance (though the 2015 test over a shorter distance was more stringent).

The team had to overcome many hurdles, including keeping the beams of photons focused on the ground stations as the satellite hurtled through space at nearly 8 kilometers per second. "Showing and demonstrating it is quite a challenging task," says Alexander Ling, a physicist at the National University of Singapore. "It's very encouraging." However, Ling notes that Pan's team recovered only about one photon out of every 6 million sent from the satellite—far better than ground-based experiments but still far too few for practical quantum communication.

Pan expects China's National Space Science Center to launch additional satellites with stronger and cleaner beams that could be detected even when the sun is shining. (Micius operates only at night.) "In the next 5 years we plan to launch some really practical quantum satellites," he says. In the meantime, he plans to use Micius to distribute quantum keys to Chinese ground stations, which will require longer strings of photons and additional steps. Then he wants to demonstrate intercontinental quantum key distribution between stations in China and Austria, which will require holding one half of an entangled photon pair on board until the Austrian ground station appears within view of the satellite. He also plans to teleport a quantum state—a technique for transferring quantum-encoded information without moving an actual object—from a third Tibetan observatory to the satellite.

Other countries are inching toward quantum space experiments of their own. Ling is teaming up with physicists in Australia to send quantum information between two satellites, and the Canadian Space Agency recently announced funding for a small quantum satellite. European and U.S. teams are also proposing putting quantum instruments on the International Space Station. One goal is to test whether entanglement is affected by a changing gravitational field, by comparing a photon that stays in the weaker gravitational environment of orbit with an entangled partner sent to Earth, says Anton Zeilinger, a physicist at the Austrian Academy of Sciences in Vienna. "There are not many experiments which test links between gravity and quantum physics."

The implications go beyond record-setting demonstrations: A network of satellites could someday connect the quantum computers being designed in labs worldwide. Pan's paper "shows that China is making the right decisions," says Zeilinger, who has pushed the European Space Agency to launch its own quantum satellite. "I'm personally convinced that the internet of the future will be based on these quantum principles."


China's quantum satellite achieves 'spooky action' at record distance | Science | AAAS

Juan Yin, Yuan Cao, Yu-Huai Li, Sheng-Kai Liao, Liang Zhang, Ji-Gang Ren, Wen-Qi Cai, Wei-Yue Liu, Bo Li, Hui Dai, Guang-Bing Li, Qi-Ming Lu, Yun-Hong Gong, Yu Xu, Shuang-Lin Li, Feng-Zhi Li, Ya-Yun Yin, Zi-Qing Jiang, Ming Li, Jian-Jun Jia, Ge Ren, Dong He, Yi-Lin Zhou, Xiao-Xiang Zhang, Na Wang, Xiang Chang, Zhen-Cai Zhu, Nai-Le Liu, Yu-Ao Chen, Chao-Yang Lu, Rong Shu, Cheng-Zhi Peng, Jian-Yu Wang, Jian-Wei Pan. Satellite-based entanglement distribution over 1200 kilometers. Science (2017). DOI: 10.1126/science.aan3211

Space calling Earth, on the quantum line
A successful quantum communication network will rely on the ability to distribute entangled photons over large distances between receiver stations. So far, free-space demonstrations have been limited to line-of-sight links across cities or between mountaintops. Scattering and coherence decay have limited the link separations to around 100 km. Yin et al. used the Micius satellite, which was launched last year and is equipped with a specialized quantum optical payload. They successfully demonstrated the satellite-based entanglement distribution to receiver stations separated by more than 1200 km. The results illustrate the possibility of a future global quantum communication network.

Science, this issue p. 1140

Abstract
Long-distance entanglement distribution is essential for both foundational tests of quantum physics and scalable quantum networks. Owing to channel loss, however, the previously achieved distance was limited to ~100 kilometers. Here we demonstrate satellite-based distribution of entangled photon pairs to two locations separated by 1203 kilometers on Earth, through two satellite-to-ground downlinks with a summed length varying from 1600 to 2400 kilometers. We observed a survival of two-photon entanglement and a violation of Bell inequality by 2.37 ± 0.09 under strict Einstein locality conditions. The obtained effective link efficiency is orders of magnitude higher than that of the direct bidirectional transmission of the two photons through telecommunication fibers.

​

 

[cirr]

Prof. Pan and team have decided to hold back on disclosing experimental results obtained on the instantaneous transmission of information:

中国“墨子”团队负责人潘建伟表示，他们已经开始实验运用量子纠缠技术创建密钥，以实现天地间的信息瞬时传输。不过潘建伟说，暂时并不准备对外公布实验结果。

 

[GS Zhou]

This is the work Pan and his team done in Dec. 2016. Since another 6 months passed, I'm curious to know their newest achievement at the current moment.

China is considering to launch a new and improved quantum satellite in two years. The new satellite can perform the quantum experiments in day time, when there are many more photons around and it is harder to pick out the ones coming from the satellite.

In addition, China has started to make the Standard on quantum communication. This is a clear signal of the commercialization of quantumn communication!

中国通信标准化协会量子通信与信息技术特设任务组成立
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文章来源：中国科学院控股有限公司 发布时间：2017-06-15 【字号： 小 中 大 】
　　6月14日上午，中国通信标准化协会量子通信与信息技术特设任务组成立暨第一次会议在北京举行。工业和信息化部党组成员、总工程师张峰，中国科学院党组成员、秘书长邓麦村，国家密码管理局商密办副主任安晓龙出席会议并致辞，会议由中国通信标准化协会副理事长兼秘书长杨泽民主持。

　　张峰在致辞中指出，量子通信技术作为第二次量子革命的代表，为信息通信产业发展提供了革命性的技术手段，成为主要发达国家和地区关注的焦点和热点，我国也已进行战略规划布局，并取得了一批重要成果。成立特设任务组，能够将标准化工作与技术创新和产业发展有机衔接，充分发挥标准对产业发展的支撑和促进作用。

　　邓麦村在致辞中强调，中科院作为国家科研机构和战略科技力量，始终高度重视量子信息技术的发展。当前，量子通信技术正处于系统集成、工程化和产业化阶段，特设任务组的成立，必将有力推动量子通信与信息技术的标准化进程，为抢占国际科技竞争和未来产业发展制高点奠定坚实基础。中科院将全力支持，与相关单位共同推动我国量子信息技术和产业的发展。

　　量子通信与信息技术特设任务组由中国科学院控股有限公司（简称“国科控股”）牵头发起，国科量子通信网络有限公司总裁戚巍当选为任务组组长并主持了任务组第一次会议，科大国盾量子技术股份有限公司总裁兼总工程师赵勇作为量子通信子组组长在会上做了题为“量子信息技术的产业机遇与挑战”的专家技术报告。

　　标准化是量子通信从实用化迈向产业化发展的关键一步，通过设立量子通信与信息技术特设任务组，开展量子信息技术方面的标准研究和制订工作，能够促进量子保密通信与现有ICT应用的灵活集成，提升量子通信网络的可扩展性和部署的灵活性，保证量子通信系统、产品及核心器件的安全性。

　　中国电信、中国移动、中国联通三大运营商以及北邮、华为、中兴、爱立信、上海贝尔等30多家会员单位的80余位代表参加了会议。

 

[TaiShang]

Spotlight: Chinese scientists successfully beam 'entangled' photons from space in landmark experiment
(Xinhua) 10:05, June 16, 2017

WASHINGTON, June 15 -- In "a major technical accomplishment" on quantum communication, Chinese scientists on Thursday reported a successful transmission of "entangled" photon pairs from space to the Earth in efforts to prove that a physical phenomenon once described by Albert Einstein as "spooky" exists at a large distance.

By distributing such entangled photons, or light particles, from a satellite 500 km above the Earth's surface, China once again demonstrates its leading position in the field of quantum research, which, though still in its infancy, has already been deemed as a competition hotspot for all major countries across the world, experts said.

The study, published as a cover story by the U.S. journal Science, "lays a reliable technical foundation for large-scale quantum networking and quantum communication experimental research, as well as experimental testing of basic principles of physics such as general theory of relativity and quantum gravity in outer space in the future," Pan Jianwei, chief scientist for Micius, the first quantum satellite in China, told Xinhua.

WORLD RECORD

Quantum entanglement, which Einstein referred to as "a spooky action at a distance," is a curious phenomenon in which particles are "linked" together in such a way that they affect one another regardless of distance. It is of great significance for secure communications, quantum computation and simulation, and enhanced metrology.

Yet, efforts to entangle quantum particles, such as photons, have been limited to about 100 km, mostly because the entanglement is lost as they are transmitted along optical fibers, or through open space on land, Pan said.

One way to overcome this issue is to break the line of transmission into smaller segments and use so-called quantum repeaters to repeatedly swap, purify and store quantum information along the optical fiber, while another approach is to make use of satellite-based technologies.

In the new study, Pan, a professor at the University of Science and Technology of China, and his colleagues used the Chinese satellite Micius, launched last year and equipped with specialized quantum tools, to demonstrate the latter feat.

The Micius satellite was used to communicate with two ground stations 1,203 km apart, located in Delingha in northwest China's Qinghai Province and Lijiang in Yunnan Province in southwest China, separately. The distance between the orbiting satellite and the two ground stations varies from 500 km to 2,000 km.

By combining so-called narrow-beam divergence with a high-bandwidth and high-precision acquiring, pointing, and tracking technique to optimize link efficiency, the team established entanglement between two single photons, separated at a distance of over 1,200 km apart, for the first time, Pan said.

In addition, compared with previous methods using the best performance and most common commercial telecommunication fibers, the effective link efficiency of the satellite-based approach is 12 and 17 orders of magnitude higher respectively.

GIANT STEP

An immediate application of distributed entangled photons, said Pan, is for entanglement-based quantum key distribution to establish secure keys for quantum communication. Another is to exploit distributed entanglement to perform a variant of quantum teleportation protocol for remote preparation and control of quantum states.

According to Pan, peer reviewers of the paper praised his work as "a major technical accomplishment with potential practical applications as well as being of fundamental scientific importance" that "will have a very large impact, both within the scientific community and in the grand public."

A number of experts spoke highly of the new achievement from China.

This demonstration of the photon entanglement distribution from a satellite to very distant ground bases is "a giant step" forward in quantum information and quantum networking development, Alexander Sergienko, a quantum physicist at Boston University, told Xinhua.

"This is a heroic experiment because so many detrimental factors were working against researchers (and) attempting to destroy a quantum nature of the photonic entanglement in this landmark experiment," Sergienko said. "It is hard to overestimate the impact of this result on the development of modern quantum physics."

"Chinese researchers deserve a greatest praise and acknowledgement of their skills, persistence, and devotion to science," said Sergienko.

Seth Lloyd, director of the Center for Extreme Quantum Information Theory at the Massachusetts Institute of Technology, expressed similar views, calling this work "a true breakthrough" in the technology of entanglement distribution.

"The experiment shows that long-range quantum communication is indeed technologically feasible and holds out the promise of the construction of long-range quantum communication networks in the near future," Lloyd told Xinhua.

QUANTUM RACE

China's Micius, with a design life of two years, was the world's first satellite launched to do quantum experiments. Teams from Canada, Germany, Austria, Singapore and other countries also have plans for quantum space experiments.

"I heard that," Pan said. "Following our first success, many groups worldwide are now trying to develop quantum science satellites or payloads."

Thomas Jennewein, an associate professor of quantum information at the University of Waterloo, who is currently pursuing a quantum communication satellite project in Canada, said that there is a "quantum space race."

"I would like to say that the Chinese group has overcome several major technical and scientific challenges and clearly demonstrated their world leadership in the field of quantum communication," Jennewein told Xinhua.

"I expect that the results from the Chinese mission will even enhance the international efforts to perform quantum satellite missions," said the expert.

 

[Bussard Ramjet]

Pan could be the next Nobel prize winner.

Yeah he could. Among a handful of Nobel Prize contenders in China.

 

[onebyone]

Quantum secure internet is possible
brian wang | June 16, 2017 |

China launched a quantum satellite called Micius from the Gobi desert last August. It is all part of a push towards a new kind of internet that would be far more secure than the one we use now. The experimental Micius, with its delicate optical equipment, continues to circle the Earth, transmitting to two mountain-top Earth bases separated by 1,200km.

The optics onboard are paramount. They’re needed to distribute to the ground stations the particles, or photons, of light that can encode the “keys” to secret messages.

“I think we have started a worldwide quantum space race,” says lead researcher Jian-Wei Pan, who is based in Hefei in China’s Anhui Province.

quantum satellite



Science – Satellite-based entanglement distribution over 1200 kilometers

A successful quantum communication network will rely on the ability to distribute entangled photons over large distances between receiver stations. So far, free-space demonstrations have been limited to line-of-sight links across cities or between mountaintops. Scattering and coherence decay have limited the link separations to around 100 km. Yin et al. used the Micius satellite, which was launched last year and is equipped with a specialized quantum optical payload. They successfully demonstrated the satellite-based entanglement distribution to receiver stations separated by more than 1200 km. The results illustrate the possibility of a future global quantum communication network.

Abstract

Long-distance entanglement distribution is essential for both foundational tests of quantum physics and scalable quantum networks. Owing to channel loss, however, the previously achieved distance was limited to ~100 kilometers. Here we demonstrate satellite-based distribution of entangled photon pairs to two locations separated by 1203 kilometers on Earth, through two satellite-to-ground downlinks with a summed length varying from 1600 to 2400 kilometers. We observed a survival of two-photon entanglement and a violation of Bell inequality by 2.37 ± 0.09 under strict Einstein locality conditions. The obtained effective link efficiency is orders of magnitude higher than that of the direct bidirectional transmission of the two photons through telecommunication fibers.

https://www.nextbigfuture.com/2017/06/quantum-secure-internet-is-possible.html

 

[Shotgunner51]

Stunning video!