How to Reconcile Maxwell’s Demon with the Second Law?_

How to Reconcile Maxwell’s Demon with the Second Law?

Ever since the nineteenth century, Maxwell’s demon has attracted a lot of attentions concerning the foundation of the second law of thermodynamics [1]. Recently, the demon has been experimentally realized [2]. The demon can adiabatically decrease the entropy of thermodynamic systems by feedback control, which seems to be a violation of the second law. A crucial question is: What reconciles the demon with the second law? In this talk, I will answer this question on the basis of our recent theoretical works [3-5]. First, I will introduce the basic concepts in information theory and nonequilibrium thermodynamics. Second, I will show that, on the basis of generalized Jarzynski equalities, the positive entropy production during measurement compensates for the negative entropy production during feedback control. Third, I will briefly review the history of Maxwell’s demon, and clarify the consistency between our results and previous researches. Our results constitute the second law of “information thermodynamics,” in which thermodynamic quantities and information contents are treated on an equal footing.

[1] “Maxwell’s demon 2: Entropy, Classical and Quantum Information, Computing,” H. S. Leff and A. F. Rex (eds.), (Princeton University Press, New Jersey, 2003).

[2] S. Toyabe, T. Sagawa, M. Ueda, E. Muneyuki, and M. Sano, Nature Physics 6, 988-992 (2010).

[3] T. Sagawa and M. Ueda, Phys. Rev. Lett. 102, 250602 (2009).

[4] T. Sagawa and M. Ueda, Phys. Rev. Lett. 104, 198904 (2010).

[5] T. Sagawa and M. Ueda, arXiv:1206.2479 (2012).

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