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arXiv · 2304.03106

Illusory cracks in the second law of thermodynamics in quantum nanoelectronics

Robert S. Whitney
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Abstract

This is a review of the theory of quantum thermodynamic demons; these are quantum systems that look like they violate the laws of thermodynamics, in analogy with Maxwell's demon. It concentrates on autonomous demons that can be made using nanoelectronics. Here ``autonomous'' means that the demon operates without any external measurement or driving, making it possible to model their entire thermodynamic behaviour using Schr\"odinger's equation. My main aim is to review why cracks in the laws of thermodynamics, sometimes glimpsed in such systems, have turned out to be illusory. For this, I work by example, introducing the methods of quantum thermodynamics via an old thought experiment that appears to break the second law. This thought experiment is usually known as Smoluchowski's trapdoor, although it was first proposed by Maxwell. Smoluchowski showed that the trapdoor's thermal motion complicates its dynamics, but I argue that he did not show that it must obey the second law. This question is now of practical relevance, because a nanoelectronic version of the trapdoor can be made with quantum dots. The methods presented here show that such a quantum trapdoor obeys the laws of thermodynamics. This reviews then addresses other types of autonomous demon that superficially appear to break the laws of thermodynamics, but which do not. These include an experimental demonstration of a Maxwell demon, and a kind of demon that exploit non-equilibrium resources (the N-demon). It discusses a way of classifying different kinds of autonomous demon. It concludes by briefly reviewing how fluctuations affect nanoelectronics, and how their role in stochastic thermodynamics changes our view of entropy.

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Robert S. Whitney. 2023-04-06. Illusory cracks in the second law of thermodynamics in quantum nanoelectronics. https://arxiv.org/abs/2304.03106

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