Quantum Mechanics ‘Locks’ Heat In Place

Scientists in Singapore have discovered how to ‘lock’ heat in place using two rotating metal rings.

AsianScientist (Aug. 13, 2019) – Researchers from the National University of Singapore (NUS) have used quantum mechanical wave theories to ‘lock’ heat into a fixed position. Their findings, published in Science, could be used to control heat diffusion in sophisticated ways and optimise efficacy in systems that need cooling.

Ordinarily, a source of heat diffuses through a conductive material until it dissipates. In this study, an NUS team led by Associate Professor Qiu Cheng-Wei used a quantum mechanics principle known as anti-parity-time (APT) symmetry to show that it is possible to confine the heat to a small region of a metal ring without it spreading over time.

“Imagine a droplet of ink in a flowing stream. After a short amount of time you would see the ink spread and flow in the direction of the current. Now imagine if that ink droplet stayed the same size and in the same position as the water flowed around it. Effectively that is what we have accomplished with the spread of heat in our experiment,” Qiu explained.

To achieve this effect, the researchers used two oppositely rotating metal rings sandwiched together with a thin layer of grease. The rotating motion of the rings act like the flow of the stream in the scenario. When heat is injected at a point in the system, the thermal energy is able to stay in position because one rotating ring is ‘coupled’ to the counter-rotating ring by the principles of APT symmetry.

“From quantum mechanical theory, you can calculate the velocity needed for the rings. Too slow or too fast, and you will break the condition,” Qiu said.

When the conditions are broken, the system acts conventionally, and the heat is carried forward as the ring rotates. Qiu and his team were able to control the heat by introducing an extra degree of freedom into their experimental setup—the rotation of the rings.

“For APT symmetry to become significant in a system, there must be some element of loss and gain within the setup, and they need to be balanced. In a traditional thermal diffusion system, APT symmetry is not consequential because there is no gain or loss degree of freedom. Hence, the mechanical rotation is the key player here,” he explained.

The team is now working on scaling up the current centimeter-sized system to the size of real motors or gears. As gearing systems often have similar counter-rotating mechanisms which generate heat, a quantum mechanical lock could help to dissipate heat more efficiently, Qiu said.

The article can be found at: Li et al. (2019) Anti–parity-time Symmetry in Diffusive Systems.


Source: National University of Singapore.
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