Harnessing higher-dimensional fluctuations in an information engine

Stemming from the ideas of Maxwell and Szilard, information engines exploit measurements of the microscopic dynamics of a system to extract heat from a thermal bath. We present an information engine consisting of an overdamped Brownian bead confined in a controllable, d-dimensional harmonic trap and subject to gravity.  The trap center is dynamically updated by a feedback protocol that performs no external work while maximizing the extraction of gravitational potential energy and achieving directed motion. We show that the engine’s performance improves strikingly when thermal fluctuations in directions orthogonal to gravity are harnessed. This enhancement arises from feedback cooling of these transverse degrees of freedom, along which all heat is extracted.  Strikingly, comparable performance can be achieved even without vertical measurements. This design modularizes the roles of fluctuation harvesting and free-energy storage, providing a fully realized experimental analog of the Szilard engine.