5/19/2023 0 Comments Nobel prize in physics![]() ![]() Such effects could allow the elements of a hidden-variable system to “conspire” together to produce measurement outcomes that mimic quantum mechanics. One of the most significant loopholes was based on the idea that the setting of Alice’s polarizer could have some influence on Bob’s polarizer or on the photons that are created at the source. The results of the first Bell test were a blow to hidden variables, but there were “loopholes” that hidden-variable supporters could claim to rescue their theory. The researchers collected 200 hours of data and found that the coincidence rates violated a revamped Bell’s inequality, proving that quantum mechanics is right. Each detector was equipped with a polarizer that could be rotated to an arbitrary orientation.įreedman and Clauser showed theoretically that quantum mechanics predictions diverge strongly from hidden variable predictions when Alice and Bob’s polarizers are offset from each other by 22.5° or 67.5°. The researchers installed two detectors (Alice and Bob) on opposite sides of the calcium source and measured the rate of coincidences-two photons hitting the detectors simultaneously. When a calcium atom de-excites, it can emit two photons whose polarizations are aligned. The Freedman-Clauser experiment used entangled photons obtained by exciting calcium atoms. The rate at which both photons went through these polarizers agreed with quantum mechanics predictions. The photons traveled to two separate polarizers, which were set at specific orientations relative to each other. The Freedman-Clauser experiment used entangled photons from excited calcium atoms. Johan Jarnestad/Royal Swedish Academy of Sciences Bell tested. Three years later, Clauser and Stuart Freedman (both at the University of California, Berkeley) succeeded in performing that experiment. A revised version using photons and polarizers was proposed in 1969 by Clauser, then at Columbia University, along with his colleagues. However, if quantum mechanics was correct, the inequality would be violated.īell’s work showed how to settle the debate between quantum and classical views, but his proposed experiment assumed detector capabilities that weren’t feasible. ![]() Bell showed that if hidden variables exist, the experimental results would obey a mathematical inequality. This time, however, the two researchers measure their respective particles in different ways and compare their results. As in Einstein’s paradox, Alice and Bob are each sent one particle of an entangled pair. That changed in 1964 when John Bell of the University of Wisconsin-Madison, proposed a thought experiment that could directly test the hidden variable hypothesis. The hidden variables were unmeasurable-by definition-so most physicists deemed their existence to be a philosophical issue, not an experimental one. To avoid such “spooky action at a distance,” Einstein proposed that lying underneath the quantum framework is a set of classical “hidden variables” that determine precisely how a particle will behave, rather than providing only probabilities. ![]() If Alice measures her particle, then she learns something about Bob’s particle-as if her measurement instantaneously changed the uncertainty about the state of his particle. He and his colleagues expressed their concern in a paradox they described in 1935 : Imagine creating two quantum mechanically entangled particles and distributing them between two separated researchers, characters later named Alice and Bob. But the theory assumes that some properties of a particle are inherently uncertain-a fact that bothered many physicists, including Albert Einstein. Since its inception, quantum mechanics has been wildly successful at predicting the outcomes of experiments. Zeilinger used some of those Bell-test techniques to demonstrate entanglement control methods that can be applied to quantum computing, quantum cryptography, and other quantum information technologies. ![]() Using entangled photons, Clauser and Aspect performed some of the first “Bell tests,” which confirmed quantum mechanics predictions while putting to bed certain alternative theories based on classical physics. The award is shared by Alain Aspect, John Clauser, and Anton Zeilinger, all of whom showed a mastery of entanglement-a quantum relationship between two particles that can exist over long distances. The Nobel Prize in Physics this year recognizes efforts to take quantum weirdness out of philosophy discussions and to place it on experimental display for all to see. ×ħ October 2022: We have replaced our initial one-paragraph announcement with a full-length Focus story. The 2022 Nobel Prize in Physics recognizes work on measuring and controlling quantum entanglement, shown here conceptually as a link between two quantum particles. ![]()
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