According to a CNRS communication dated October 29, 2025. Based on a scientific publication in Physical Review Letters to which Ludovic Bellon, a CNRS researcher at ENS de Lyon’s Physics Laboratory (LPENSL), contributed: "Information Engine Fueled by First-Passage Times." Thumbnail image: a Brownian particle (subject to thermal agitation) wanders in a confined well until it reaches a threshold, where an automated system (a demon) acts on the position of the well to extract energy from the particle. © Aubin Archambault, Caroline Crauste-Thibierge, Alberto Imparato, Christopher Jarzynski, Sergio Ciliberto, Ludovic Bellon.
Researchers have revisited the famous "Maxwell’s demon" experiment, supplementing its description with the temporal information managed by the demon to create a state of non-equilibrium. This approach resolves the paradox of the "free" creation of energy and establishes a quantitative description of the links between information and energy.
An engine powered solely by energy pumped from the environment would create perpetual motion, a situation that 19th-century thermodynamicists proved impossible. However, an exception to this ironclad rule, which stems from the second law of thermodynamics, can be envisioned if we can cleverly use information obtained elsewhere about the microscopic state of a system, as in Maxwell’s famous thought experiment: in this thought experiment, an "intelligent being" (the demon) measures the speed of gas molecules in order to sort them, without expending energy. This information about speed can then be used to create a temperature difference that can be harnessed to push a piston and thus create motion from an environment in equilibrium, thereby contradicting the second law. This contradiction is, of course, only apparent, because if we reintroduce into the balance the entire mechanical chain associated with measuring the information obtained, the second law is verified overall.
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Reference
Information Engine Fueled by First-Passage Times, Aubin Archambault, Caroline Crauste-Thibierge, Alberto Imparato, Christopher Jarzynski, Sergio Ciliberto , Ludovic Bellon, Physical Review Letters 135, 147101 - Published on 2 October 2025. DOI: 10.1103/s9kj-lczm
