3 Scientists Share Nobel Prize In Physics For Work In Quantum Mechanics

A victory for quantum physics

Three researchers jointly won this year’s Nobel Prize in physics Tuesday for proving that small particles can retain a connection with each other even when separated, a phenomenon in quantum physics once questioned now being explored for potential real-world applications like encrypting data.

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

All of it returns to a feature of the universe that even baffled Albert Einstein and linked matter and light in a twisted, chaotic method.

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

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

Yet the trio’s experiments revealed it occurs in reality.

A new perspective

” Why this happens, I have not the foggiest,” Clauser informed The Associated Press during one Zoom interview in which he received the official call from the Swedish Academy many hours after friends and media told him of his award. “I don’t understand how it works, but entanglement seems very real.”

His fellow winners also said they can not describe the how and why behind this effect. However, each did ever more intricate experiments that show it just is.

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

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

Aspect said Einstein may have been technically incorrect, however, deserves massive credit for raising the right issue that led to experiments proving quantum entanglement.

” Most people would assume that nature is made out of things distributed throughout space and time,” stated Clauser, who, while a high school student in the 1950s constructed a video game on one vacuum tube computer. “And that seems not to be the situation.”

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

This hard-to-understand field started with idea experiments. However, what, in one sense, is philosophical musings about the universe likewise hold hope for more secure and faster computer systems, all based on entangled photons and matter that still interact no matter how distant.

” With my 1st 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 benefits nothing. I’m doing this simply out of curiosity.'”.

The mystery of quantum entanglement

In quantum entanglement, establishing common information between 2 photons not near each other “enables us to do things like secret communication, in forms which were not possible to do before,” stated David Haviland, chair of the Nobel Committee for Physics.

Quantum data “has broad and potential implications in areas like secure data transfer, quantum computer, and sensing technology,” stated Eva Olsson, one member of the Nobel committee. “Its predictions opened doors to another world, and it has also shaken the foundations of how we interpret measurements.”.

The type of secure communication utilized by China’s Micius satellite and some banks is a “success story of quantum entanglement,” stated Harun Siljak of Trinity University Dublin. Using one entangled particle to produce an encryption key ensures that only the person with the other entangled particle can decode the message, and “the secret shared between these 2 sides is a proper secret,” Siljak stated.

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

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

” I assume we have progress toward the quantum computer. I would not state that we are close,” the 75-year-old physicist stated. “I do not know if I will observe it in my life. But I am an old man.”.

Speaking by phone to one news conference after the announcement, the College of Vienna-based Zeilinger stated he was “still kind of surprised” at hearing he had received the award.

The Nobel prize recipients

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

The Nobel committee stated Clauser developed quantum theories first put forward in the 1960s into a practical experiment. The aspect closed a loophole in those concepts, while Zeilinger showed a phenomenon called quantum teleportation that effectively enables information to be transmitted over distances.

” Using entanglement, you can transfer all the data that is carried by an object over to some other location where the object is, so to speak, reconstituted,” Zeilinger stated. He included that this only functions for tiny particles.

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

One week of Nobel Prize announcements kicked off Monday with Swedish researcher Svante Paabo receiving the award in medicine Monday for revealing secrets of Neanderthal DNA that provided vital insights into our immune system.

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

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

Nobel Committee press release: The Nobel Prize in Physics 2022

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2022 to:

Alain Aspect

Université Paris-Saclay and
École Polytechnique, Palaiseau, France

John F. Clauser

J.F. Clauser & Assoc., Walnut Creek, CA, U.S.

Anton Zeilinger

College of Vienna, Austria

” for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.”

Entangled states– from theory to technology

Alain Aspect, John Clauser, and Anton Zeilinger have each conducted groundbreaking experiments using entangled quantum states, where 2 particles behave like a single unit also when they are divided. Their outcome have cleared the way for recent technology based upon quantum information.

The ineffable effects of quantum mechanics are starting to find applications. There is currently a large field of research that includes quantum computers, quantum networks, and secure quantum encrypted communication.

One crucial factor in this development is how quantum mechanics enables two or more particles to exist in what is called an entangled state. What occurs to one of the particles in an entangled pair determines what occurs to the other particle, even if they are far apart.

For a long time, the question was whether the correlation was because the particles in an entangled pair contained hidden variables, instructions that tell them which outcome they should give in an experiment. In the 1960s, John Stewart Bell developed the mathematical inequality that is named after him. This states that if there are hidden variables, the correlation between the outcomes of a large number of measurements will never exceed a specific value. However, quantum mechanics predicts that a certain kind of experiment will violate Bell’s inequality, hence resulting in a stronger correlation than would otherwise be possible.

Entanglement and physics

John Clauser developed John Bell’s theories, leading to a practical experiment. When he took the measurements, they supported quantum mechanics by plainly violating a Bell inequality. This means that an approach that uses hidden variables cannot replace quantum mechanics.

Some loopholes remained after John Clauser’s experiment. Alain Aspect developed the setup, utilizing it in a way that closed an important loophole. He could switch the measurement settings after an entangled pair had left its source, so the setting that existed when they were emitted could not affect the outcome.

Using refined devices and long experiments, Anton Zeilinger started to use entangled quantum states. Among other things, his research study group has demonstrated a phenomenon called quantum teleportation that makes it possible to move one quantum state from one particle to one at a distance.

” It has become increasingly clear that a new type of quantum technology is emerging. We can observe that the laureates’ work with entangled states is of high importance, even beyond the fundamental questions about the interpretation of quantum mechanics,” states Anders Irbäck, Chair of the Nobel Committee for Physics.

How entanglement has become a powerful device

Using groundbreaking experiments, Alain Aspect, John Clauser, and Anton Zeilinger have shown the potential to investigate and control particles that are in entangled states. What occurs to one particle in an entangled pair determines what happens to the other, even if they are really too much apart to affect each other. The laureates’ development of experimental devices has laid the foundation for a new age of quantum technology.

The fundamentals of quantum mechanics are not only a theoretical or philosophical issues. Intense research and development are underway to utilize the unique properties of individual particle systems to construct quantum computers, improve measurements, develop quantum networks, and establish secure quantum encrypted communication.

Many applications rest upon how quantum mechanics enable two or more particles to exist in a shared state, regardless of how much apart they are. This is named entanglement and has been one of the most discussed elements of quantum mechanics ever since the concept was formulated. Albert Einstein talked about spooky action at a distance, and Erwin Schrödinger stated it was quantum mechanics’ most important trait.

This year’s laureates have explored these entangled quantum states, and their experiments laid the foundation of the revolution now underway in quantum technology.

Far from everyday experience

When two particles remain in entangled quantum states, someone that measures a property of one bit can immediately determine the outcome of an equivalent measurement on the other particle without requiring to check.

What makes quantum mechanics so special is that its equivalents to the balls have no determined states until they are measured. It is as if both the balls are grey, right up until someone observes at one of them. Then, it can randomly take either all the black the pair of balls has access to or can show itself to be white. The other ball immediately turns the contrary color.

But how is it possible to understand that the balls did not each have a set color at the beginning? Even if they appeared grey, perhaps they had a hidden label inside, stating which color they would turn when someone looks at them.

Does color exist when no one is watching?

Quantum mechanics’ entangled pairs could be compared to a machine that throws out balls of contrary colors in contrary directions. When Bob catches one ball and sees that it is black, he immediately knows that Alice has caught a white one. In a theory that uses hidden variables, the balls had always contained hidden data about what color to reveal. However, quantum mechanics states that the balls were grey until someone looked at them when one randomly turned white and the other black. Bell inequalities reveal that there are experiments that could differentiate between these cases. Such experiments have proven that quantum mechanics’ description is correct.

An essential part of the research being rewarded with this year’s Nobel Prize in Physics is a theoretical insight called Bell inequalities. Bell inequalities make it possible to differentiate between quantum mechanics’ indeterminacy and an alternative description utilizing secret instructions or hidden variables. Experiments have shown that nature acts as predicted by quantum mechanics. The balls are grey, with no secret data, and chance determines which becomes black and which becomes white in an experiment.

Quantum mechanics’ most important resource

Entangled quantum states hold the potential for new ways of storing, transferring, and processing information.

Interesting things happen if the particles in an entangled pair travel in opposite directions. One of them then meets a third particle in such a manner that they become entangled. They then enter a new shared state. The third particle loses its identity, but its initial properties have currently been transferred to the solo particle from the original pair. This way of moving an unknown quantum state from one particle to another is called quantum teleportation. This type of experiment was first conducted in 1997 by Anton Zeilinger and his colleagues.

Remarkably, quantum teleportation is the only way to transfer quantum information from one system to another without losing any part of it. It is absolutely impossible to measure all the properties of a quantum system and then send the information to a recipient that wants to reconstruct the system. This is because a quantum system can simultaneously contain several versions of every property, where each version has a certain probability of appearing during a measurement. As soon as the size is conducted, only one version remains, namely the one that was read by the measuring instrument. The others have disappeared, and it is impossible to ever know anything about them. However, entirely unidentified quantum properties can be transferred using quantum teleportation and appear intact in another particle, but at the price of them being destroyed in the original particle.

Once this had been shown experimentally, the next step was to use two pairs of entangled particles. Suppose one particle from each set are brought together in a particular way. In that case, the undisturbed particles in each set can become entangled despite never having been in contact with each other. This entanglement swapping was first demonstrated in 1998 by Anton Zeilinger’s research group.

Entangled sets of photons, light particles, can be sent in opposite directions through optical fibers and function as signals in a quantum network. Entanglement between two pairs makes it possible to extend the distances between the nodes in such a network. There is a limit to the distance that photons can be sent through an optical fiber before they are absorbed or lose their properties. Ordinary light signals can be amplifed along the way, but this does not work with entangled sets. An amplifer has to capture and measure the light, which breaks the entanglement. Nonetheless, entanglement swapping means it is possible to send the original state further, thereby transferring it over longer distances than had otherwise been possible.

Entangled particles that never met

Two sets of entangled particles are emitted from different sources. One particle from each set is brought together in a unique way that entangles them. The two other particles (1 and 4 in the diagram) are then likewise entangled. In this way, 2 particles that have never been in contact can become entangled.

From paradox to inequality

This progress rests on many years of development. It started with the mind-boggling insight that quantum mechanics allows a single quantum system to be divided up into parts that are separated from each other but which still act as a single unit.

This goes against all the usual ideas about cause and effect and the nature of reality. How can something be influenced by an event occurring somewhere else without being reached by some form of signal from it? A signal can not travel faster than light– but in quantum mechanics, there does not seem to be any need for a signal to connect the different parts of an extended system.

Albert Einstein regarded this as unfeasible and examined this phenomenon, along with his colleagues Boris Podolsky and Nathan Rosen. They presented their reasoning in 1935: quantum mechanics does not appear to provide a complete description of reality. This has come to be called the EPR paradox after the researchers’ initials.

The question was whether there could be a more complete description of the world, where quantum mechanics is just one part. This could, for example, work through particles always carrying hidden information about what they will show as the result of an experiment. All the measurements then show the properties that exist exactly where the measurements are conducted. This type of information is often called local hidden variables.

The Northern Irish physicist John Stewart Bell (1928– 1990) that worked at CERN, the European particle physics laboratory, took a closer look at the problem. He discovered that there is a kind of experiment that can determine whether the world is purely quantum mechanical or whether there could be another description with hidden variables. If his experiment is repeated many times, all theories with hidden variables reveal a correlation between the results that must be lower than, or at most equal to, a specific value. This is called Bell’s inequality.

Nonetheless, quantum mechanics can violate this inequality. It predicts greater values for the correlation between the outcomes than is possible through hidden variables.

John Clauser became interested in the fundamentals of quantum mechanics as a student in the 1960s. He could not shake of John Bell’s idea once he had read about it, and, eventually, he and three other researchers were able to present a proposal for a realistic type of experiment that could be used to test a Bell inequality.

The experiment involves sending a set of entangled particles in opposite directions. In practice, photons that have a property called polarisation are used. When the particles are emitted the direction of the polarization is undetermined, and all that is certain is that the particles have parallel polarization. This can be investigated using a filter that allows through polarisation that is oriented in a particular direction (see figure Experimenting with Bell inequalities). This is the effect used in many sunglasses, which block light that has been polarised in a specific plane, for example, by reflecting of water.

If both the particles in the experiment are sent towards filters that are oriented in the same plane, such as vertically, and one slips through–, then the other one will likewise go through. If they are at right angles to each other, one will be stopped while the other will go through. The trick is to measure with the filters set in different directions at skewed angles, as then the results can vary: sometimes both slide through, sometimes just one, and sometimes none. How often both particles get through the filter depends on the angle between the filters.

Quantum mechanics leads to a correlation between measurements. The likelihood of one particle getting though depends on the angle of the filter that tested its partner’s polarisation on the opposite side of the experimental setup. This means that the results of both measurements, at some angles, violate a Bell inequality and have a stronger correlation than they would if the results were governed by hidden variables and were currently predetermined when the particles were emitted.

Violated inequality

John Clauser immediately began working on conducting this experiment. He built an apparatus that emitted 2 entangled photons at a time, each towards a filter that tested their polarization. In 1972, along with doctoral student Stuart Freedman (1944– 2012), he was able to show a result that was a clear violation of a Bell inequality and agreed with the predictions of quantum mechanics.

In the years following, John Clauser and other physicists continued discussing the experiment and its limitations. One of these was that the experiment was generally inefficient, both when it came to producing and capturing particles. The measurement was also pre-set, with the filters at fixed angles. There were, therefore, loopholes where an observer could question the results: what if the experimental setup in some way selected the particles that happened to have a strong correlation and did not detect the others? If so, the particles could still be carrying hidden information.

Eliminating this particular loophole was hard because entwined quantum states are so fragile and difficult to manage; it is necessary to deal with individual photons. French doctoral student Alain Aspect was not intimidated and built one new version of the setup that he refined over many iterations. In his experiment, he could register the photons that passed through the filter and those that did not. This meant more photons were detected, and the measurements were better.

In the final variant of his tests, he was also able to steer photons towards two different filters that were set at different angles. The finesse was a mechanism that switched the direction of the entangled photons after they had been created and emitted from their source. The filters were just six meters away, so the switch needed to occur in a few billionths of a 2nd. If information about which filter the photon would arrive at influenced how it was emitted from the source, it would not be arriving at that filter. Nor could info concerning the filters on one side of the experiment reach the other side and affect the measurement result there.

In this way, Alain Aspect closed a crucial loophole and offered a very clear outcome: quantum mechanics is correct, and there are no hidden variables.

The age of quantum information

These and similar experiments laid the foundation for the present intense research in quantum information science.

Being able to manipulate and manage quantum states and all their layers of properties offers us access to devices with unexpected potential. This is the basis for quantum computation, the transfer and storage of quantum information, and algorithms for quantum encryption. Systems with more than 2 particles, all of which are entangled, are currently in use, which Anton Zeilinger and his colleagues were the 1st to explore.

Experimenting with Bell inequalities

Anton Zeilinger later conducted more tests of Bell inequalities. He created entangled sets of photons by shining a laser on a special crystal and also utilized random numbers to shift between measurement settings. One experiment used signals from distant galaxies to control the filters and ensure the signals could not affect each other.

These increasingly advanced tools bring realistic applications closer. Entangled quantum states have currently been demonstrated between photons that have been sent through tens of kilometers of optical fiber and between a satellite and a station on the ground. Researchers worldwide have found numerous new ways to utilize the most potent property of quantum mechanics in a short time.

The 1st quantum revolution gave us transistors and lasers; however, we are now entering a new era thanks to contemporary devices for manipulating systems of entangled particles.

Read the original article on PHYS.

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