An engine manipulated by a “demon” can generate more work than would be expected from basic thermodynamics, but whether a quantum demon can outperform a classical demon is still an open question. A new experimental study shows that correlations—specifically a type of correlation called quantum steering—can allow more work to be extracted from an atomic-scale engine than classically allowed [1].

A demon—like the one imagined by the physicist Leo Szilárd in 1929—can measure particles inside an engine and then use that information to configure the engine so that more work is generated. Despite appearances, this enhanced output is not a violation of thermodynamic limits, as the demon’s information gathering factors into the entropy budget (see Viewpoint: Maxwell’s Demon Meets Nonequilibrium Quantum Thermodynamics).

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