Download presentation

Presentation is loading. Please wait.

Published byHelena Bettridge Modified over 2 years ago

1
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.

2
Physics of Information Making a measurement

3
Physics of Information What is information?

4
Physics of Information Information processing

5
Exorcise Maxwell’s (mechanical) demon Consider intelligent beings as demons “Universal law” of measurements

6
Second Law of Thermodynamics

8
Maxwell: “The 2 nd law is only statistically valid. “Could statistical fluctuations be exploited to run a perpetual motion machine?”

9
Maxwell’s Demon Exploiting fluctuations

10
Ratchet and pawl

11
Getting hit means Getting heat!

12
Forward Step Stretch ε Lift Lθ Fluctuation Lθ+ε

13
Forward Step Rate Stretch ε Lift Lθ Fluctuation Lθ+ε

14
Backward Step Fluctuation ε Drop Lθ Release Lθ+ε

15
Backward Step Rate Fluctuation ε Drop Lθ Release Lθ+ε

16
Reversible process

17
The engine keeps 2 nd law

18
Trap door demon Mechanical demons fluctuate

19
Ranque-Hilsch vortex tube (1933)

20
Szilard: “Under what circumstances could we construct a perpetual motion machine, utilizing intelligent beings?”

22
Concerns of intelligent demons

23
Making measurements Processing information Erasing information

24
Szilard’s first machine Intelligent being couples parameters

25
Szilard’s first machine Work done at the expense of heat

26
ENTROPY BILL Ideal gas: Heat reservoir:

27
ENTROPY BILL The frequency of each outcome: Overall we get:

29
ENTROPY BILL Ansatz: Overall we get:

30
Szilard’s second machine

32
ENTROPY BILL If parameter (x) thermalizes reversibly: Ansatz:

33
ENTROPY BILL Overall we get: Szilard’s Universal Law:

34
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

35
Szilard’s third machine

40
ENTROPY BILL

42
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

43
Summary Szilard assumes the 2 nd law A “universal law” of measurements

44
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.

45
So what is intelligence?

Similar presentations

OK

Chapter 15 Thermodynamics. 15.1 Thermodynamic Systems and Their Surroundings Thermodynamics is the branch of physics that is built upon the fundamental.

Chapter 15 Thermodynamics. 15.1 Thermodynamic Systems and Their Surroundings Thermodynamics is the branch of physics that is built upon the fundamental.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google