A Potential Quantum Exception To The Second Law Of Thermodynamics

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If you want something to be mad at for your misfortunes in physics, there’s no better candidate than the second law of thermodynamics. Things breaking down, aging, and even death depend on that physical law, which states that the entropy of the universe tends to increase.

Researchers from the Argonne National Laboratory (ANL) looked at the second law in the quantum world and were able to reformulate an important theorem according to the rules of quantum mechanics. In doing so, they found that the theorem allowed for a quantum violation of the second law.

The researchers worked on a branch of science called quantum information, which takes information theory – math applied to communication – to the quantum level. Information and entropy show remarkably similar formulas and scientists working in either field have been borrowing heavily from each other.

One of these formulae is the H-theorem, which demonstrates that it is possible to see an irreversible increase in entropy from a reversible process. To put it simply, if you open your front door, eventually the air in your home will be at the same temperature as the air outside. The only way to recreate a difference in temperature is to spend energy in doing so.

The team was able to formulate a quantum information theory of entropy and looked at what would happen if it was applied to solids or liquids.

"This allowed us to formulate the quantum H-theorem as it related to things that could be physically observed," said co-author Ivan Sadovskyy from ANL in a statement. "It establishes a connection between well-documented quantum physics processes and the theoretical quantum channels that make up quantum information theory."

The research is published in Scientific Reports, and it shows that the H-theorem might be violated under certain conditions.

Since our first understanding of the second law, people have been trying to find violations and exceptions, like the famous thought experiment known as Maxwell’s demon. In the house door example, the demon would be a gatekeeper letting only molecules of a certain temperature in or out, making sure that the house and the rest of the world remain at different temperatures.

"Although the violation is only on the local scale, the implications are far-reaching," said co-author Valerii Vinokur, also from ANL. "This provides us a platform for the practical realization of a quantum Maxwell's demon, which could make possible a local quantum perpetual motion machine."

This quantum violation might not work in practice, though, so the researchers are collaborating with a team of experimentalists to see if it is possible to get around the second law of thermodynamics.

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