Temporal information: an efficient fuel for a microscopic engine!
Researchers have revisited the famous "Maxwell's demon" experiment, supplementing its description with the temporal information managed by the demon to create a non-equilibrium state. This approach resolves the paradox of the "free" creation of energy and establishes a quantitative description of the links between information and energy.
References :
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 2 October, 2025.
DOI: 10.1103/s9kj-lczm
Open Archives: arxiv, HAL
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 envisaged if we manage to cleverly use information obtained elsewhere about the microscopic state of a system, as in the famous thought experiment devised by Maxwell: 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 on speed thus makes it possible to create a temperature difference that can be used to push a piston and thus create movement 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 the measurement of the information obtained, the second law is verified overall.
The present study was carried out in the following CNRS laboratory:
Laboratoire de Physique de l’ENS de Lyon (LPENSL, CNRS / ENS de Lyon)
In a recent study, a team of researchers from an international collaboration proposed a new experiment performing a Maxwell demon, using an original definition of information based not on position or speed but on the time required for a fluctuating mechanical system to reach a given position (see figure). This process powers a microscopic motor very efficiently, with researchers demonstrating theoretically and experimentally that the conversion of temporal information into energy is almost perfect. Furthermore, this information can be easily measured and satisfies a new theorem at the intersection of information theory and stochastic thermodynamics. Beyond this specific achievement, the proposed definition of information based on the time taken to reach a set point provides a new tool that can be used to analyse other experiments measuring fluctuations at microscopic scales. These results are published in Physical Review Letters.
