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Open AccessArticle

A Programmable Mechanical Maxwell’s Demon

1,*,† and 2,3,4,*,†
James Franck Institute, University of Chicago, Chicago, IL 60637, USA
Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
Department of Physics, University of Maryland, College Park, MD 20742, USA
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Entropy 2019, 21(1), 65;
Received: 21 November 2018 / Revised: 22 December 2018 / Accepted: 9 January 2019 / Published: 14 January 2019
(This article belongs to the Special Issue Thermodynamics of Information Processing)
PDF [4111 KB, uploaded 14 January 2019]


We introduce and investigate a simple and explicitly mechanical model of Maxwell’s demon—a device that interacts with a memory register (a stream of bits), a thermal reservoir (an ideal gas) and a work reservoir (a mass that can be lifted or lowered). Our device is similar to one that we have briefly described elsewhere, but it has the additional feature that it can be programmed to recognize a chosen reference sequence, for instance, the binary representation of π . If the bits in the memory register match those of the reference sequence, then the device extracts heat from the thermal reservoir and converts it into work to lift a small mass. Conversely, the device can operate as a generalized Landauer’s eraser (or copier), harnessing the energy of a dropping mass to write the chosen reference sequence onto the memory register, replacing whatever information may previously have been stored there. Our model can be interpreted either as a machine that autonomously performs a conversion between information and energy, or else as a feedback-controlled device that is operated by an external agent. We derive generalized second laws of thermodynamics for both pictures. We illustrate our model with numerical simulations, as well as analytical calculations in a particular, exactly solvable limit. View Full-Text
Keywords: Maxwell’s demon; Shannon entropy; information engine; Landauer’s principle; Szilard engine; second law of thermodynamics Maxwell’s demon; Shannon entropy; information engine; Landauer’s principle; Szilard engine; second law of thermodynamics

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Lu, Z.; Jarzynski, C. A Programmable Mechanical Maxwell’s Demon. Entropy 2019, 21, 65.

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