title: Second laws for an information driven current through a spin valve.
abstract: We propose a physically realizable Maxwell's demon device using a spin valve interacting unitarily for a short time with electrons placed on a tape of quantum dots, which is thermodynamically equivalent to the device introduced by Mandal and Jarzynski [D. Mandal and C. Jarzynski, Proc. Natl. Acad. Sci. USA 109, 11641 (2012)]. The model is exactly solvable and we show that it can be equivalently interpreted as a Brownian ratchet demon. We then consider a measurement-based discrete feedback scheme, which produces identical system dynamics, but possesses a different second law inequality. We show that the second law for discrete feedback control can provide a smaller, equal, or larger bound on the maximum extractable work as compared to the second law involving the tape of bits. Finally, we derive an effective master equation governing the system evolution for Poisson distributed bits on the tape (or measurement times, respectively) and we show that its associated entropy production rate contains the same physical statement as the second law involving the tape of bits.
authors.affiliation: Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Strasberg
authors.affiliation: Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany.
authors.forename: Gernot
authors.initials: G
authors.lastname: Schaller
authors.affiliation: Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Brandes
authors.affiliation: Department of Chemistry and Biochemistry and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Jarzynski