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Physics

Quantum theory is challenging long-standing ideas about entropy

A mathematical study finds that three definitions of what it means for entropy to increase, which have previously been considered equivalent, can produce different results in the quantum realm

By Karmela Padavic-Callaghan

15 October 2024

Quantum theory is poking holes in our understanding of entropy

VICTOR de SCHWANBERG/SCIENCE PHOTO LIBRARY

Measuring disorder in the quantum realm is creating a bit of a mess. A mathematical study found that three different definitions of entropy that were previously thought to be equivalent don’t always match for quantum objects. This could have far-reaching implications, as it could force a rewrite of well-established models for thermodynamics.

When two objects are connected – say a container of hot gas is linked to a colder gas reservoir – the entropy of the colder one can increase because the two will…

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