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Related Concept Videos

Entropy01:18

Entropy

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The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
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Entropy and the Second Law of Thermodynamics01:20

Entropy and the Second Law of Thermodynamics

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The second law of thermodynamics can be stated quantitatively using the concept of entropy. Entropy is the measure of disorder of the system.
The relation  between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...
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Entropy Change in Reversible Processes01:10

Entropy Change in Reversible Processes

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In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
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The Second Law of Thermodynamics01:14

The Second Law of Thermodynamics

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In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Scientists refer to the measure of randomness or disorder within a system as entropy. High entropy means high disorder and low energy. To better understand entropy, think of a student’s bedroom. If no energy or work were put into it, the room would quickly become messy. It would exist in a very disordered state, one of high entropy. Energy must be...
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Second Law of Thermodynamics02:49

Second Law of Thermodynamics

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In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic...
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Entropy within the Cell01:22

Entropy within the Cell

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A living cell's primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers in the universe are completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, heat energy is defined as the energy transferred from one system to another that...
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Entropy production from maximum entropy principle: A unifying approach.

Adalberto D Varizi1, Pedro S Correia1

  • 1Departamento de Ciências Exatas e Tecnológicas, <a href="https://ror.org/01zwq4y59">Universidade Estadual de Santa Cruz</a>, 45662-900, Ilhéus, Bahia, Brazil.

Physical Review. E
|September 19, 2024
PubMed
Summary

This study unifies definitions of entropy production, a key concept in thermodynamics, by using the maximum entropy principle. It provides a general framework applicable to quantum measurements and quantum channels.

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Area of Science:

  • Thermodynamics
  • Quantum Information Theory
  • Statistical Mechanics

Background:

  • Entropy production quantifies irreversible processes and is central to the second law of thermodynamics.
  • Current definitions of entropy production lack universal consensus, leading to conflicting interpretations.
  • Entropy production is fundamentally linked to information incompleteness.

Purpose of the Study:

  • To establish a unified framework for defining entropy production.
  • To reconcile prominent and seemingly contradictory definitions of entropy production.
  • To extend the definition of entropy production to quantum systems with incomplete information.

Main Methods:

  • Application of Jaynes' maximum entropy principle.
  • Development of a general framework for entropy production.
  • Analysis of tomographically incomplete quantum measurements.
  • Investigation of quantum channel actions on quantum systems.

Main Results:

  • A unified definition of entropy production is established.
  • The framework successfully integrates diverse existing definitions.
  • The definition is applicable to scenarios with incomplete quantum information.

Conclusions:

  • The maximum entropy principle provides a robust foundation for defining entropy production.
  • This work resolves ambiguities and offers a consistent approach to entropy production.
  • The generalized definition enhances the understanding of irreversible processes in quantum information science.