Presentation on theme: "Physics of Information Yovav Kalifon Weizmann Inst. 18 Nov 2008 Szilard, L. (1929) `On the Decrease of Entropy in a Thermodynamic System by the Intervention."— Presentation transcript:
Physics of Information Yovav Kalifon Weizmann Inst. 18 Nov 2008 Szilard, L. (1929) `On the Decrease of Entropy in a Thermodynamic System by the Intervention of Intelligent Beings', Zeitschrift für Physik 53, 840 ¯ 856. Feynman, Feynman Lectures on Physics, Ratchet and Pawl, Volume 1, Chapter 46. Landauer, R. (1961) `Irreversibility and Heat Generation in the Computing Process', Advances in Chemical Physics 5, 183 ¯ 191.
ENTROPY BILL If parameter (x) thermalizes reversibly: Ansatz:
ENTROPY BILL Overall we get: Szilard’s Universal Law:
The entropy of erasure Landauer (1961) and Bennet (1982): A measurement is essentially copying Computation can be made reversible Erasing memory means compressing the phase space of possible physical states, inevitably heating up the environment
Summary Simple demons fail due to Brownian motion Intelligent demons are a part of the system Demons make up for the missing entropy No perpetual motion machine is known
Summary Szilard assumes the 2 nd law A “universal law” of measurements
Summary Szilard’s own work supports the claim that erasing memory is the only stage which necessarily raises the entropy of the system Inanimate automatic machines can measure parameters, store the information, process it, even print the result.