It has been found that the universe is not real. An apple can be red even if no one is looking, and a local object can only be influenced by its surroundings. The things can't both be true according to investigations at the frontiers of quantum physics. The evidence shows that objects are not influenced solely by their surroundings and that they may lack certain properties before being measured. Albert Einstein once said, "Do you really believe the moon is not there when you are not looking at it?"

This is contrary to what we experience every day. The demise of local realism has made a lot of people angry and has been seen as a bad move by the public.

Three physicists are to blame for this achievement, they are John Clauser, Aspect and Zeilinger Experiments with entangled photons, establishing the violation of Bell inequalities, and quantum information science were some of the pioneers of the field. The Bell inequalities refers to the work of the Northern Irish physicist John Stewart Bell, who laid the groundwork for this year's physics prize. The trio deserved this punishment for overthrowing reality. It is wonderful. Sandu Popescu is a quantum physicist at the University ofBristol. The prize is well- deserved.


Charles Bennett, a quantum researcher at IBM, says that the experiments beginning with the earliest one of Clauser show that this stuff isn't just theoretical, it's real.

David Kaiser is a physicist at the Massachusetts Institute of Technology. It was. It was very exciting and emotional.

The journey from fringe to favor was lengthy. The topic was often seen as philosophy at best and crackpottery at worst. It was nearly impossible to get papers in quantum foundations published in scientific journals. Popescu was warned against taking a PhD in the subject by his advisor. Popescu says that he was told that if he did that, he would be out of a job.

Quantum information science is one of the most important subfields in physics. Black holes are linked to Einstein's general theory of relativity by the still-mysterious behavior. More and more, quantum sensors are being used to study everything from earthquakes to dark matter. It helps clarify the nature of quantumentanglement, a phenomenon that is crucial to modern materials science and that is at the heart of quantum computing.

There is a quantum computer. A National Institute of Standards and Technology physicist asked rhetorically. One of the most popular answers is entanglement, and the main reason why we understand it is the work done by Bell and the other winners of the prize. We wouldn't be able to realize quantum computers without that understanding.


For Whom the Bell Tolls

The problem with quantum mechanics was not that it made the wrong predictions, but that they were accurate from the beginning.

The theory's uncomfortable implications for reality was what Einstein, Boris Podolsky and NathanRosen took issue with. To illustrate the absurdity of quantum mechanics, their analysis centered on a thought experiment meant to show how under certain conditions the theory can break, or at least deliver nonsensical results that conflict with reality. A simplified and modernized version of EPR goes like this: Pairs of particles are sent off in different directions from a common source, targeted for Alice and Bob, each stationed at opposite ends of the solar system. It's not possible to know the spin of individual particles before they're measured. Alice finds her particle's spin to be either up or down when she measures it. She instantly knows that Bob's particle must be down when she measures up. The particles are similar to a pair of socks, and if Alice gets the right one, Bob must have the left one.

Particles are not like socks and only when measured do they settle on a spin. How do they know what Bob's particles will do when they fly out of the solar system in the other direction if Alice's particles don't have a spin until measurement? Alice asks her particle what Bob will get if he flips a coin. One in 10 60 is more than the number of atoms in the solar system. Despite the billions of kilometers that separate the particle pairs, quantum mechanics says Alice's particles can still predict, as if they were connected to Bob's particles.

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The results of real-world versions of the EPR thought experiment reinforce the theory. Nature is not real under quantum mechanics because particles don't have spin up or spin down before measurement, and seem to talk to one another no matter the distance.

Physicists who were skeptical of quantum mechanics proposed that there were hidden variables that existed in some imperceptible level of reality beneath the subatomic realm that contained information about a particle's future state. They wanted nature to recover the local realism denied to it by quantum mechanics.


According to Popescu, one would have thought that the arguments of Einstein, Podolsky and Rosen would lead to a revolution at that time.

Physicists, who by and large accept quantum mechanics as is, didn't catch on to Einstein's " attack" on quantum mechanics. A head-in- the-sand sentiment later summarized by the physicist David Mermin was a demand to "shut up and calculate."

John von Neumann published a mathematical proof in 1932 that ruled out hidden-variable theories. Three years later, a young female mathematician, Grete Hermann, rejected Neumann's proof, but no one seemed to notice.

Until Bell shattered the problem of nonlocal realism, quantum mechanics was in a state of disrepair. Bell was sympathetic towards hidden variable theories from the beginning. He was inspired by the idea of a nonlocal hidden interpretation of quantum mechanics when he heard of David Bohm's work. Bell considered the ideas for a long time as a side project to his main job.

The same flaws were found in von Neumann's argument. The question of hidden variables was dragged onto the ground of experiment by Bell in a triumph of rigorous thought.


Indistinguishable experimental outcomes are usually predicted by hidden-variable theories. Bell realized that an empirical discrepancy between the two can be found. Alice and Bob received the same particles in the Bell test, but now they have different detector settings. The settings on the detector allow Alice and Bob to ask different questions. Particles can't outsmart this extra step in local hidden-variable theories where their state is preordained and nothing links them. Particles are much more correlated in quantum mechanics than they are in local theories. They are not free from one another.

It's possible to prove which theory was correct by measuring the correlation multiple times. If the correlation remained below a limit derived from Bell's theorem, this would suggest hidden variables were real, and if it exceeded Bell's limit, the mind- incomprehensible tenets of quantum mechanics would reign supreme. In spite of its potential to help determine the nature of reality, after being published in a journal, it remained undiscovered for years.

The Bell Tolls for Thee

John Clauser was a graduate student at Columbia University when he accidentally stumbled across a library copy of Bell's paper. Clauser asked if anyone had actually done the test. Bell got the first feedback from Clauser.

The first Bell test was performed by Clauser and his student. Clauser had secured permission from his supervisors, but little in the way of funds, so he became an expert at "dumpster diving" to secure equipment. Clauser used a kayak-sized apparatus that required careful tuning by hand to send pairs of photons in opposite directions to the detectors.

They concluded that they had found strong evidence against Clauser after they finished their analysis. The result was not conclusive because of various "loopholes" in the experiment that could allow hidden variables to slip through. If either the photon source or the detectors could somehow share information, the resulting measured correlations could still emerge from hidden variables. Kaiser says that interference makes it difficult to rule out hidden variables.


It's difficult to close the locality loophole. The setting of the detector needs to be changed quickly because the photon are on the fly. The ultra-speedy switch was proposed by a French expert in 1976. Clauser's results were only strengthened by his group's experimental results. Bell said that Nature is not so queer as quantum mechanics. The experimental situation isn't very encouraging.

Bell died without seeing the closing of the loopholes. Aspect's experiment was too small a distance to completely rule out local effects. Clauser realized that if Alice and Bob weren't guaranteed to detect an unbiased sample of particles, they would reach the wrong conclusions.

No one could have done more to close these loopholes. He and his team improved on their earlier work by conducting a Bell test over a long distance. The era of divining reality was over. The group tackled multiple loopholes at the same time.

I wanted to be an engineer before quantum mechanics. The Bell experiment was a giant systems-engineering project according to a quantum researcher who worked with it. One requirement for creating an experiment closing multiple loopholes was to find a perfectly straight, empty 60-meter tunnel. The dungeon of Vienna's Hofburg palace was an almost ideal setting, aside from being caked with a century's worth of Dust. Their results were published in 2015, along with similar tests from two other groups.

Bell’s Test Reaches the Stars

There was still one great final loophole that needed to be closed. Any previous physical connection between components can affect the validity of a Bell test. They share a past if Alice shakes Bob's hand before she leaves. There is a chance that a local hidden-variable theory could exploit these loopholes.

The team performed a bell test. The team used telescopes in the Canary Islands to find random settings from stars that would not allow light from one to reach the other for a long time. Even then, quantum mechanics was victorious.

It's difficult to explain the importance of Bell tests to the public because of the perception that quantum mechanics was a foregone conclusion. Many aspects of quantum mechanics have been measured to a precision of more than 10 parts in a billion. I didn't want to do anything with it. I thought it was old physics. "'We all know what's going to happen' Bell tests were the only ones that could rule out the possibility of hidden variables.

The question "Can the world work that way?" was the one that drew each of the recipients to the topic. Kaiser said so. How do we know if we're doing the right thing? Physicists can use Bell tests to remove the bias of aesthetic judgments from the equation, as well as remove the parts of human cognitive theory that recoil at the possibility of eerily inexplicable entanglement. It is testament to all the researchers who were unhappy with superficial explanations about quantum mechanics that they were honored with the award.

Bell tests are a good way to look at reality.