Classical Model Explains Light-Matter Interaction In Quantum World

In the quantum world, all the standard rules don’t apply. Now, researchers have created a model that describes a quantum phenomenon in a classical way.

AsianScientist (Aug. 11, 2016) – A team of scientists from Okinawa Institute of Science and Technology Graduate University in Japan has shown that what was thought to be a quantum phenomenon can be explained classically. Their results were published in Physical Review Letters.

Physicists study the tiny particles—neutrons, electrons, photons—that make up our classical world either one at a time or in small numbers, because the behavior of the particles is completely different on such a small scale. If you add to the number of particles that are being studied, eventually there will be enough particles that they no longer act quantum mechanically and must be identified as classical, just like our everyday world. But where do we draw the line between the quantum world and the classical world?

“We wanted to know about the relationship and interactions between light and matter,” said study author Professor Denis Konstantinov of OIST Graduate University. “By light, we mean electromagnetic fields: radio waves, microwaves, or light. They are all described by the same laws in physics. By matter, we mean a collection of tiny particles, like atoms or electrons.”

Specifically, the team was interested in strong coupling, a phenomenon generally thought of as a quantum effect. Strong coupling is when the light and the matter are both affected by the interactions. This is unusual as in most circumstances, the light is not affected by the interaction, similar to how a boat in the ocean is affected by the waves, but the ocean is not really affected by the presence of the boat.

To see whether this type of strong coupling could be explained classically, the researchers took a collection of electrons from the surface of liquid helium, which exists at very low temperatures. They then brought the electrons into a cavity containing electromagnetic microwaves where the electrons and waves could interact.

“We saw strong changes in the electromagnetic wave frequency while they were interacting with the electrons and strong changes in the electrons’ activity as well,” Konstantinov said. “This is a signature of strong coupling.”

From there, they successfully created a classical model that described the phenomenon of strong coupling that they observed experimentally. This meant that strong coupling with large amounts of particles could be categorized in the classical world instead of the quantum world as previously thought.

Understanding strong coupling and their relation to qubits, or units of quantum information, could be significant for the development of quantum computing, the researchers ssay.


The article can be found at: Abdurakhimov et al. (2016) Strong Coupling of the Cyclotron Motion of Surface Electrons on Liquid Helium to a Microwave Cavity.

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Source: OIST.
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