NASA REPROTS ON quantum entanglement...

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Quantum entanglement: the 'spooky' science behind physics Nobel

This year's physics Nobel prize was awarded Tuesday to three men for their work on a phenomenon called quantum entanglement, which is so bizarre and unlikely that Albert Einstein was sceptical, famously calling it "spooky".

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So how exactly does it work?

Even people with degrees in physics struggle to understand it -- and some who do still find parts "hard to swallow," said Chris Phillips, a physicist at Imperial College London.

To explain the phenomenon he used the example of a photon -- "a single unit of light" -- though the theory is believed to hold true for other particles.

If a photon is put through a "special crystal", it can be split into separate photons, he told AFP.

"They're different colours from the one you started with," Phillips said, "but because they started from one photon, they are entangled".

This is where it gets weird. If you measure one photon it instantly affects the other -- no matter how far you separate them.

This is not supposed to happen. Einstein's theory of relativity says nothing can travel faster than the speed of light.

And they are inextricably bound together. When you observe the first photon, there are even odds that it will show itself as "either up or down", Phillips said. But if it is up, then its twin is instantly forced down, or vice versa.

- New way to kill Schroedinger's cat -

He extended the famous quantum thought experiment of Schroedinger's cat, in which a hypothetical animal locked inside a box with a flask of poison remains simultaneously alive and dead -- until the moment the box is opened.

For quantum entanglement, if you have two cats in two boxes, by opening one you would "kill that cat and instantaneously -- on the other side of the universe -- the other cat has been killed," Phillips said.

Phillips has seen this "extremely strange thing" first hand in his laboratory, where he has two beams of photons set up.

"I can put my hand in one beam and something happens to the other beam on the other side of the room instantaneously -- I see a needle flick," he said.

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"That would still be true if my laboratory was millions of miles across."

It was the fact that this occurs instantly that bothered Einstein, who dismissed this element of quantum entanglement -- called non-locality -- as "spooky action at a distance" in 1935.

He instead believed that "hidden variables" must somehow be behind what was happening.

In 1964, influential physicist John Stewart Bell found a way to measure whether there were in fact hidden variables inside quantum particles.

Two decades later, French physicist Alain Aspect, who won the Nobel on Tuesday, and his team were among the first able to test Bell's theory in a laboratory.

By testing its limits, they found that "quantum mechanics resists all possible attacks," Aspect said in an interview published by the Nobel Foundation after his win on Tuesday.

- 'Totally crazy'

In doing so, Aspect proved Einstein wrong. But he was magnanimous to history's greatest physicist.

"I like to say that Einstein's owes a great, great merit in raising the question," Aspect said, adding that "non-locality does not allow you to send a useful message faster than light".

Even Aspect finds it weird to have accepted the idea of something "totally crazy" like non-locality into "my mental images," he said.

The other physics Nobel winners, Austria's Anton Zeilinger and John Clauser of the US, also tested Bell's theory, ruling out loopholes and helping pave the way for what has been called the "second quantum revolution".

Discoveries by Zeilinger, dubbed the "quantum pope", have shown the potential for quantum entanglement to be used in encryption, quantum teleportation and more.

Phillips from Imperial College London has developed a prototype the size of a hi-fi sound system that uses quantum entanglement to diagnose breast cancer.

But perhaps the greatest mystery about quantum entanglement remains one that puzzled Einstein nearly a century ago: why does it occur?

"We have to be humble in the face of physics," Phillips said, adding that it was the same as any another aspect of nature.

"It just is."

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Three physicists win the Nobel for work on quantum entanglement

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“Is nature a trickster?” On Tuesday, the Nobel Committee posed this question regarding what may be nature’s slightest sleight of hand: quantum mechanics.

Quantum mechanics is an area of physics that deals with all things subatomic. This field throws a wrench into pre-existing classical physics, which gave us the Standard Model that explains three of the universe’s four forces and identifies all known subatomic particles. Quantum mechanics endeavors to predict where a particle will be at any given moment. Simple stuff.

There’s one especially tricky aspect of quantum mechanics known as entanglement. This phenomenon occurs when two particles, even if they’re far from each other, act in unison. Effects on one particle will also impact its pair. Even though they’re separate, they operate as a single unit. Einstein described this behavior as “spooky action at a distance.”

This year, Alain Aspect, John Clauser, and Anton Zeilinger share the Nobel Prize in Physics for their respective contributions to quantum mechanics, demonstrating not only its theoretical capacities but also showing that photons in entangled states are all around us.

How it all started — Irish physicist John Stewart Bell published a 1964 paper developing a mathematical inequality known as Bell’s inequality. According to this principle, if hidden variables exist within the entangled pair, then the correlation between results of a large number of measurements will always remain within certain boundaries.

Quantum mechanics, however, says that some kind of experiment will violate Bell’s inequality. This violation implicates a stronger correlation than thought possible between two particles.

How this changed science as we know it — American John Clauser created a practical experiment from Bell’s theory. He’s the one who found the experiment that violated Bell’s inequality while supporting quantum mechanics, meaning that a theory using hidden variables can’t replace quantum mechanics.

Alain Aspect of France further built on this finding, closing a loophole in Clauser’s finding. He modified the experiment’s measurement settings after an entangled pair had launched from its source. The existing setting then couldn’t affect the resulting 

measurements.

Austrian Anton Zeilinger toyed with these entangled quantum states. His research depicted a principle called quantum teleportation, in which one particle can move quantum states over a distance.

Why these discoveries are important — A goal of quantum mechanics, the Nobel Committee says, is to build a quantum network. They describe this network as a series of nodes that use quantum entanglement to communicate. This network has applications in encryption and quantum computing, which can synthesize astronomical amounts of information.

Understanding entanglement is key since it’s what ties this network together. However, entanglement is brittle and comes apart in optical fibers meant to transmit it.

Recipient Anton Zeilinger said on a call when the award was publicly announced that the next generation will be the ones to build on the remaining questions. "This prize is an encouragement to young people," he said. He also acknowledged the more than 100 students he had worked with to even get this far. While physicists have made strides in this area, there's still a long way to go.

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3 physicists share Nobel Prize for work on quantum science

They demonstrated that unseen particles, such as photons, can be linked, or “entangled,” with each other even when they are separated by large distances.

STOCKHOLM, Sweden — Three scientists jointly won this year’s Nobel Prize in physics Tuesday for proving that tiny particles could retain a connection with each other even when separated, a phenomenon once doubted but now being explored for potential real-world applications such as encrypting information.

Frenchman Alain Aspect, American John F. Clauser and Austrian Anton Zeilinger were cited by the Royal Swedish Academy of Sciences for experiments proving the “totally crazy” field of quantum entanglements to be all too real. They demonstrated that unseen particles, such as photons, can be linked, or “entangled,” with each other even when they are separated by large distances.

It all goes back to a feature of the universe that even baffled Albert Einstein and connects matter and light in a tangled, chaotic way.

Bits of information or matter that used to be next to each other even though they are now separated have a connection or relationship — something that can conceivably help encrypt information or even teleport. A Chinese satellite now demonstrates this and potentially lightning fast quantum computers, still at the small and not quite useful stage, also rely on this entanglement. Others are even hoping to use it in superconducting material.

“It's so weird,” Aspect said of entanglement in a telephone call with the Nobel committee. “I am accepting in my mental images something which is totally crazy.”

Yet the trio's experiments showed it happen in real life.

“Why this happens I haven't the foggiest,” Clauser told The Associated Press during a Zoom interview in which he got the official call from the Swedish Academy several hours after friends and media informed him of his award. “I have no understanding of how it works but entanglement appears to be very real.”

His fellow winners also said they can't explain the how and why behind this effect. But each did ever more intricate experiments that prove it just is.

Clauser, 79, was awarded his prize for a 1972 experiment, cobbled together with scavenged equipment, that helped settle a famous debate about quantum mechanics between Einstein and famed physicist Niels Bohr. Einstein described “a spooky action at a distance” that he thought would eventually be disproved.

“I was betting on Einstein,” Clauser said. “But unfortunately I was wrong and Einstein was wrong and Bohr was right.”

Aspect said Einstein may have been technically wrong, but deserves huge credit for raising the right question that led to experiments proving quantum entanglement.

“Most people would assume that nature is made out of stuff distributed throughout space and time," said Clauser, who while a high school student in the 1950s built a video game on a vacuum tube computer. "And that appears not to be the case.”

What the work shows is “parts of the universe — even those at great distances from each other — are connected,” said Johns Hopkins physicist N. Peter Armitage. “This is something so unintuitive and something so at odds with how we feel the world ‘should’ be.”

This hard-to-understand field started with thought experiments. But what in one sense is philosophical musings about the universe also holds hope for more secure and faster computers all based on entangled photons and matter that still interact no matter how distant.

“With my first experiments I was sometimes asked by the press what they were good for,” Zeilinger, 77, told reporters in Vienna. “And I said with pride: ‘It’s good for nothing. I’m doing this purely out of curiosity.’”

In quantum entanglement, establishing common information between two photons not near each other "allows us to do things like secret communication, in ways which weren’t possible to do before,” said David Haviland, chair of the Nobel Committee for Physics.

Quantum information “has broad and potential implications in areas such as secure information transfer, quantum computing and sensing technology," said Eva Olsson, a member of the Nobel committee. "Its predictions have opened doors to another world, and it has also shaken the very foundations of how we interpret measurements.”

The kind of secure communication used by China’s Micius satellite — as well as by some banks — is a “success story of quantum entanglement,” said Harun Siljak of Trinity College Dublin. By using one entangled particle to create an encryption key, it ensures that only the person with the other entangled particle can decode the message and "the secret shared between these two sides is a proper secret,” Siljak said.

While quantum entanglement is “incredibly cool” security technologist Bruce Schneier, who teaches at Harvard, said it is fortifying an already secure part of information technology where other areas, including human factors and software are more of a problem. He likened it to installing a side door with 25 locks on an otherwise insecure house.

At a news conference, Aspect said real-world applications like the satellite were “fantastic.”

“I think we have progress toward quantum computing. I would not say that we are close," the 75-year-old physicist said. “I don’t know if I will see it in my life. But I am an old man.”

Speaking by phone to a news conference after the announcement, the University of Vienna-based Zeilinger said he was “still kind of shocked” at hearing he had received the award.

Clauser, Aspect and Zeilinger have figured in Nobel speculation for more than a decade. In 2010 they won the Wolf Prize in Israel, seen as a possible precursor to the Nobel.

The Nobel committee said Clauser developed quantum theories first put forward in the 1960s into a practical experiment. Aspect was able to close a loophole in those theories, while Zeilinger demonstrated a phenomenon called quantum teleportation that effectively allows information to be transmitted over distances.

“Using entanglement you can transfer all the information which is carried by an object over to some other place where the object is, so to speak, reconstituted," Zeilinger said. He added that this only works for tiny particles.

“It is not like in the Star Trek films (where one is) transporting something, certainly not the person, over some distance,” he said.

A week of Nobel Prize announcements kicked off Monday with Swedish scientist Svante Paabo receiving the award in medicine Monday for unlocking secrets of Neanderthal DNA that provided key insights into our immune system.

Chemistry is on Wednesday and literature on Thursday. The Nobel Peace Prize will be announced Friday and the economics award on Oct. 10.

The prizes carry a cash award of 10 million Swedish kronor (nearly $900,000) and will be handed out on Dec. 10. The money comes from a bequest left by the prize’s creator, Swedish dynamite inventor Alfred Nobel, who died in 1895.