Involves the non-Abelian Aharonov-Bohm Effect and is reported today in the journal Science. The finding relates to gauge fields, which describe transformations that particles undergo. Gauge fields fall into two classes, known as Abelian and non-Abelian.
The Aharonov-Bohm Effect, named after the theorists who predicted it in 1959, confirmed that gauge fields—beyond being a pure mathematical aid—have physical consequences. But the observations only worked in Abelian systems, or those in which gauge fields are commutative—that is, they take place the same way both forward and backward in time. In 1975, Tai-Tsun Wu and Chen-Ning Yang generalized the effect to the non-Abelian regime as a thought experiment. Nevertheless, it remained unclear whether it would even be possible to ever observe the effect in a non-Abelian system. Physicists lacked ways of creating the effect in the lab, and also lacked ways of detecting the effect even if it could be produced. Now, both of those puzzles have been solved, and the observations carried out successfully.
The effect has to do with one of the strange and counter intuitive aspects of modern physics, the fact that virtually all fundamental physical phenomena are time-invariant. That means that the details of the way particles and forces interact can run either forward or backward in time, and a movie of how the events unfold can be run in either direction, so there's no way to tell which is the real version. But a few exotic phenomena violate this time symmetry. Creating the Abelian version of the Aharonov-Bohm effects requires breaking the time-reversal symmetry, a challenging task in itself. To achieve the non-Abelian version of the effect requires breaking this time-reversal multiple times, and in different ways, making it an even greater challenge.
To produce the effect, the researchers use photon polarization. Then, they produced two different kinds of time-reversal breaking. They used fiber optics to produce two types of gauge fields that affected the geometric phases of the optical waves, first by sending them through a crystal biased by powerful magnetic fields, and second by modulating them with time-varying electrical signals, both of which break the time-reversal symmetry. They were then able to produce interference patterns that revealed the differences in how the light was affected when sent through the fiber-optic system in opposite directions, clockwise or counterclockwise. Without the breaking of time-reversal invariance, the beams should have been identical, but instead, their interference patterns revealed specific sets of differences as predicted, demonstrating the details of the elusive effect.
At this point, the experiment is primarily of interest for fundamental physics research, with the aim of gaining a better understanding of some basic underpinnings of modern physical theory.
https://phys.org/news/2019-09-exotic-physics-phenomenon.html
The Aharonov-Bohm Effect, named after the theorists who predicted it in 1959, confirmed that gauge fields—beyond being a pure mathematical aid—have physical consequences. But the observations only worked in Abelian systems, or those in which gauge fields are commutative—that is, they take place the same way both forward and backward in time. In 1975, Tai-Tsun Wu and Chen-Ning Yang generalized the effect to the non-Abelian regime as a thought experiment. Nevertheless, it remained unclear whether it would even be possible to ever observe the effect in a non-Abelian system. Physicists lacked ways of creating the effect in the lab, and also lacked ways of detecting the effect even if it could be produced. Now, both of those puzzles have been solved, and the observations carried out successfully.
The effect has to do with one of the strange and counter intuitive aspects of modern physics, the fact that virtually all fundamental physical phenomena are time-invariant. That means that the details of the way particles and forces interact can run either forward or backward in time, and a movie of how the events unfold can be run in either direction, so there's no way to tell which is the real version. But a few exotic phenomena violate this time symmetry. Creating the Abelian version of the Aharonov-Bohm effects requires breaking the time-reversal symmetry, a challenging task in itself. To achieve the non-Abelian version of the effect requires breaking this time-reversal multiple times, and in different ways, making it an even greater challenge.
To produce the effect, the researchers use photon polarization. Then, they produced two different kinds of time-reversal breaking. They used fiber optics to produce two types of gauge fields that affected the geometric phases of the optical waves, first by sending them through a crystal biased by powerful magnetic fields, and second by modulating them with time-varying electrical signals, both of which break the time-reversal symmetry. They were then able to produce interference patterns that revealed the differences in how the light was affected when sent through the fiber-optic system in opposite directions, clockwise or counterclockwise. Without the breaking of time-reversal invariance, the beams should have been identical, but instead, their interference patterns revealed specific sets of differences as predicted, demonstrating the details of the elusive effect.
At this point, the experiment is primarily of interest for fundamental physics research, with the aim of gaining a better understanding of some basic underpinnings of modern physical theory.
https://phys.org/news/2019-09-exotic-physics-phenomenon.html
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