scholarly journals The original Wigner’s friend paradox within a realist toy model

2021 ◽  
Vol 477 (2254) ◽  
Author(s):  
Matteo Lostaglio ◽  
Joseph Bowles
Keyword(s):  
Thought Experiment ◽  
Classical Model ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Unitary Evolution ◽  
Apparent Lack ◽  
External Agent ◽  
Wigner’S Friend ◽  
Objective State ◽  
State Of Affairs

The original Wigner’s friend paradox is a gedankenexperiment involving an observer described by an external agent. The paradox highlights the tension between unitary evolution and collapse in quantum theory, and is sometimes taken as requiring a reassessment of the notion of objective reality. In this note, however, we present a classical toy model in which (i) the contradicting predictions at the heart of the thought experiment are reproduced (ii) every system is in a well-defined state at all times. The toy model shows how puzzles such as Wigner’s friend’s experience of being in a superposition, conflicts between different agents’ descriptions of the experiment, the positioning of the Heisenberg’s cut and the apparent lack of objectivity of measurement outcomes can be explained within a classical model where there exists an objective state of affairs about every physical system at all times. Within the model, the debate surrounding the original Wigner’s friend thought experiment and its resolution have striking similarities with arguments concerning the nature of the second law of thermodynamics. The same conclusion however does not apply to more recent extensions of the gedankenexperiment featuring multiple encapsulated observers, and shows that such extensions are indeed necessary avoid simple classical explanations.

scholarly journals The second law of thermodynamics under unitary evolution and external operations

2015 ◽  
Vol 354 ◽  
pp. 338-352 ◽  
Author(s):  
Tatsuhiko N. Ikeda ◽  
Naoyuki Sakumichi ◽  
Anatoli Polkovnikov ◽  
Masahito Ueda
Keyword(s):  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Unitary Evolution

scholarly journals Maxwell’s Demon in Quantum Mechanics

Entropy ◽  
2020 ◽  
Vol 22 (3) ◽  
pp. 269
Author(s):  
Orly Shenker ◽  
Meir Hemmo
Keyword(s):  
Quantum Mechanics ◽  
Thought Experiment ◽  
Classical Mechanics ◽  
Second Law Of Thermodynamics ◽  
Quantum Mechanical ◽  
Second Law ◽  
Arrow Of Time ◽  
Maxwell’S Demon ◽  
Counter Example ◽  
Maxwell's Demon

Maxwell’s Demon is a thought experiment devised by J. C. Maxwell in 1867 in order to show that the Second Law of thermodynamics is not universal, since it has a counter-example. Since the Second Law is taken by many to provide an arrow of time, the threat to its universality threatens the account of temporal directionality as well. Various attempts to “exorcise” the Demon, by proving that it is impossible for one reason or another, have been made throughout the years, but none of them were successful. We have shown (in a number of publications) by a general state-space argument that Maxwell’s Demon is compatible with classical mechanics, and that the most recent solutions, based on Landauer’s thesis, are not general. In this paper we demonstrate that Maxwell’s Demon is also compatible with quantum mechanics. We do so by analyzing a particular (but highly idealized) experimental setup and proving that it violates the Second Law. Our discussion is in the framework of standard quantum mechanics; we give two separate arguments in the framework of quantum mechanics with and without the projection postulate. We address in our analysis the connection between measurement and erasure interactions and we show how these notions are applicable in the microscopic quantum mechanical structure. We discuss what might be the quantum mechanical counterpart of the classical notion of “macrostates”, thus explaining why our Quantum Demon setup works not only at the micro level but also at the macro level, properly understood. One implication of our analysis is that the Second Law cannot provide a universal lawlike basis for an account of the arrow of time; this account has to be sought elsewhere.

scholarly journals Entropy and Maxwell’s Demon: The Degree of Disorderliness in Concept

2021 ◽  
Vol 01 (1) ◽  
pp. 14-18
Author(s):  
Bijan K. Paul ◽  
Keyword(s):  
Present Article ◽  
Thought Experiment ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Maxwell’S Demon ◽  
Maxwell's Demon

The present article is motivated toward delving into the concept of entropy, a fundamental consequence of the second law of thermodynamics with particular emphasis on the thought experiment by James C. Maxwell, famously known as the “Maxwell’s demon”, which in turn enables our visualization of the connection of entropy with information.

scholarly journals An Observable Prerequisite for the Existence of Persistent Currents

2018 ◽  
Author(s):  
Jacob Szeftel ◽  
Nicolas Sandeau ◽  
Michel Abou Ghantous
Keyword(s):  
Classical Model ◽  
Second Law Of Thermodynamics ◽  
Superconducting Materials ◽  
Second Law ◽  
Persistent Currents ◽  
Joule Effect ◽  
Ohm’S Law ◽  
Normal Metals ◽  
Superconducting Sample ◽  
Ohm's Law

A classical model is presented for persistent currents in superconductors. Their existence is argued to be warranted because their decay would violate the second law of thermodynamics. This conclusion is achieved by analyzing comparatively Ohm's law and the Joule effect in normal metals and superconducting materials. Whereas Ohm's law applies in identical terms in both cases, the Joule effect is shown to cause the temperature of a superconducting sample to \textit{decrease}. An experiment is proposed to check the validity of this work in superconductors of both types I and II.

scholarly journals Gibbs Distribution from Sequentially Predictive Form of the Second Law

2021 ◽  
Vol 185 (1) ◽  
Author(s):  
Ken Hiura
Keyword(s):  
Empirical Distribution ◽  
Random Number Generator ◽  
Heat Engine ◽  
Second Law Of Thermodynamics ◽  
Testing Procedure ◽  
Gibbs Distribution ◽  
Second Law ◽  
Control Parameters ◽  
Strong Law ◽  
External Agent

AbstractWe propose a prequential or sequentially predictive formulation of the work extraction where an external agent repeats the extraction of work from a heat engine by cyclic operations based on his predictive strategy. We show that if we impose the second law of thermodynamics in this situation, the empirical distribution of the initial microscopic states of the engine must converge to the Gibbs distribution of the initial Hamiltonian under some strategy, even though no probability distribution are assumed. We also propose a protocol where the agent can change only a small number of control parameters linearly coupled to the conjugate variables. We find that in the restricted situation the prequential form of the second law of thermodynamics implies the strong law of large numbers of the conjugate variables with respect to the control parameters. Finally, we provide a game-theoretic interpretation of our formulation and find that the prequential work extraction can be interpreted as a testing procedure for random number generator of the Gibbs distribution.

scholarly journals Hidden Dissipation and Irreversibility in Maxwell’s Demon

Entropy ◽  
2022 ◽  
Vol 24 (1) ◽  
pp. 93
Author(s):  
Paul W. Fontana
Keyword(s):  
Thought Experiment ◽  
A Priori ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
External Work ◽  
Maxwell’S Demon ◽  
Thermodynamic Irreversibility ◽  
Maxwell's Demon ◽  
Stringent Limit ◽  
Thermodynamic Limits

Maxwell’s demon is an entity in a 150-year-old thought experiment that paradoxically appears to violate the second law of thermodynamics by reducing entropy without doing work. It has increasingly practical implications as advances in nanomachinery produce devices that push the thermodynamic limits imposed by the second law. A well-known explanation claiming that information erasure restores second law compliance fails to resolve the paradox because it assumes the second law a priori, and does not predict irreversibility. Instead, a purely mechanical resolution that does not require information theory is presented. The transport fluxes of mass, momentum, and energy involved in the demon’s operation are analyzed and show that they imply “hidden” external work and dissipation. Computing the dissipation leads to a new lower bound on entropy production by the demon. It is strictly positive in all nontrivial cases, providing a more stringent limit than the second law and implying intrinsic thermodynamic irreversibility. The thermodynamic irreversibility is linked with mechanical irreversibility resulting from the spatial asymmetry of the demon’s speed selection criteria, indicating one mechanism by which macroscopic irreversibility may emerge from microscopic dynamics.

First and second laws of thermodynamics: relationship, “inconsistency”, hidden effects

2020 ◽  
pp. 63-73
Author(s):  
A. M. Savchenko ◽  
Yu. V. Konovalov ◽  
A. V. Laushkin
Keyword(s):  
Free Energy ◽  
Internal Energy ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Entropy Of Mixing ◽  
Ideal Mixing ◽  
Laws Of Thermodynamics ◽  
Relationship Of ◽  
The Relationship

The relationship of the first and second laws of thermodynamics based on their energy nature is considered. It is noted that the processes described by the second law of thermodynamics often take place hidden within the system, which makes it difficult to detect them. Nevertheless, even with ideal mixing, an increase in the internal energy of the system occurs, numerically equal to an increase in free energy. The largest contribution to the change in the value of free energy is made by the entropy of mixing, which has energy significance. The entropy of mixing can do the job, which is confirmed in particular by osmotic processes.

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