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Tuesday, 18 June 2019

Discovered non-Newtonian force, a quantum force that can act at a distance

"Quantum force"

It is not any day that a physicist discovers a new force, still less a "quantum force."

So when Maria Becker and her colleagues at the University of Nebraska-Lincoln submitted their article describing the existence of a non-Newtonian force, the magazine asked them to put "force" firmly in quotation marks.

After all, this word belongs from the beginning to classical Newtonian physics: Equal and opposing reactions, electromagnetism, gravity, and other laws that explain the phenomena of everyday experience, like the apple that falls from the tree.

But Maria Becker and her colleagues are using the word in the context of quantum physics, which describes the infinitesimally small, where the position and velocity of subatomic particles are defined by probabilities, not by precise values, where electrons behave simultaneously as particles and as waves, and where other counterintuitive inaccuracies govern the kingdom.

The metal rod, the magnetic field around it and the electron beam, revealing the "quantum force". [Image: Becker et al. - 10.1038 / s41467-019-09609-9]

Aharonov, Bohm, Zeilinger and Berry

This kingdom became even more confusing in 1959 when an experiment was suggested in which the mere proximity of a classical force - instead of force itself - could be imposed on the physical world. In the experiment, two streams of electrons travel on each side of a coil whose magnetic field is totally shielded from these electrons.

Despite the fact that none of the electron fluxes passes through the real magnetic field, researchers have determined that the quantum probabilities of electrons undergo measurable changes that depend on the strength of the magnetic field. Later experiments confirmed the presence of this so - called Aharonov-Bohm effect .

But if the existence of this strange effect was indisputable, his nature was not. Anton Zeilinger, who had already put causality in check , introduced a theorem suggesting that the Aharonov-Bohm effect does not represent or result from a force. Years later, however, physicists Andrei Shelankov and Michael Berry countered by stating that the Aharonov-Bohm effect arises from the quantum equivalent of a force. Even if this force does not retard the electrons, Shelankov predicted that this could change its flight trajectories, bypassing them slightly.

"In each case, you can understand the derivation of each theory," said Herman Batelaan, a staff member who has now discovered "quantum force." "The two seem right, but they are in conflict with each other, so we break our heads to elaborate a theory that gives the two answers." We understood that there should be a larger structure. begged for an experiment. "

Then, Maria Becker set herself a grand goal: to demonstrate Shelankov's prediction and, at the same time, accommodate the Zeilinger theorem.

The transfer of information without using particles also describes a non-local behavior, with wide uses in quantum computing . [Image: Qi Guo et al. - 10.1038 / srep08416]

Non-Newtonian force

The experiment, carried out at the University of Antwerp in Belgium, reminds many of those who preceded it: Electron beams sailing towards a nanoscopic rod whose magnetic field is protected from particles. When the magnetization of the rod is zero, the wave patterns that the electrons form after reflecting on the shield - patterns similar to ripples superimposed on the water - have been symmetrical.

However, as the team increased magnetization, these diffraction patterns became asymmetric - an indirect sign of a non-Newtonian force poking electrons left or right. And as the team hoped, reversing the direction of magnetization also reversed the direction of asymmetry, further supporting the idea of ​​a quantum phenomenon that can affect matter in ways similar to classical Newtonian forces.

What about the Zeilinger theorem? According to the team's analysis, the theoretical assumptions he made do not apply to the lateral movement implicit in the experiment. Given this, Batelaan states that the study does not invalidate Zeilinger. Instead, the team mathematically demonstrated that its results, provided by Shelankov, and the Zeilinger theorem are two special cases of a more comprehensive theorem.

Batelaan compared the situation to a ball that begins to roll along a flat platform. Raising and lowering this platform slowly can change the destination of the ball in the plane even if its speed and time of arrival remain the same. Looking at the underside of the platform, an observer might not notice any change, which may become apparent only after a change of perspective.

Physicists have long struggled with hidden influences that can exist beyond spacetime . [Image: Yasdani Group / Princeton] 

Non-local nature

The issue of perspective also grounds the interpretation of the study, Batelaan said. Classical forces operate locally, affecting only matter adjacent to these forces. But quantum mechanics - notably the quantum entanglement, by which changes in one particle manifest simultaneously in another tangled particle that could theoretically be light years away - is not limited by distance, it is nonlocal.

In this way, the results can be interpreted as evidence of a similarly nonlocal force.

"Here we have a situation that is nonlocal but different from quantum entanglement," Batelaan said. "It is a phenomenon of a particle, not a phenomenon of two particles." So, could this idea of ​​things happening without a force be applied in a different context? idea that nature can be nonlocal.This is the big question.Are the things I do here affect things elsewhere without a clear middleman? "

Finding evidence of a non-local 'force' does not mean that the researcher liked the idea - it can not be forgotten that, equally, Einstein disdained quantum entanglement by calling it phantasmagoric action at a distance .

"I find it disgusting," said Batelaan with laughter. "I live in the classical world, everything I see around me, I see happening because of forces." If there are things going on without strength, why can not I use them? Why are there no more examples of this? As a physical principle, it must be everywhere, but we are possibly simply too blind to see it. "


Asymmetry and non-dispersivity in the Aharonov-Bohm effect
Maria Becker, Giulio Guzzinati, Armand Béché, Johan Verbeeck, Herman Batelaan Nature Communications
Vol. 10, Article number: 1700
DOI: 10.1038 / s41467-019-09609-9

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