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Entropy Change in Reversible Processes01:10

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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.
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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.
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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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Quantum-Classical Entropy Analysis for Nonlinearly-Coupled Continuous-Variable Bipartite Systems.

Ángel S Sanz1

  • 1Department of Optics, Faculty of Physical Sciences, Universidad Complutense de Madrid, Pza. Ciencias 1, Ciudad Universitaria, 28040 Madrid, Spain.

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|February 25, 2022
PubMed
Summary
This summary is machine-generated.

Investigating classical analogs of quantum states, this study reveals that entropy measures delocalization and correlations, not entanglement production, in coupled quartic oscillators. These findings bridge quantum and classical descriptions in phase space.

Keywords:
Wigner distribution functionentanglemententropy measurementopen quantum systemsquantum dynamicsquantum foundationsquantum–classical correspondence

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Area of Science:

  • Quantum Mechanics
  • Statistical Mechanics
  • Chaos Theory

Background:

  • The correspondence principle is crucial in quantum mechanics, prompting exploration of classical analogs for quantum states in phase space.
  • Wigner distribution functions are used to represent quantum states in phase space, but contain interference terms.
  • Understanding the relationship between quantum and classical descriptions is key to unifying these fields.

Purpose of the Study:

  • To investigate classical analogs of quantum states by removing interference terms from Wigner functions.
  • To compare the dynamical evolution of quantum and classical entropies in a bipartite system.
  • To analyze the behavior of these entropies under regular and chaotic conditions for different quantum states.

Main Methods:

  • Numerical computation of linear and von Neumann entropies for a continuous-variable bipartite system.
  • Investigating two nonlinearly coupled quartic oscillators.
  • Considering Gaussian, cat, and Bell-type quantum states.

Main Results:

  • Entropies quantify system delocalization (both quantum and classical) rather than entanglement production.
  • An increase in entropy correlates with increased correlations between system parts.
  • Quantum entanglement is linked to increased correlations, mirroring classical behavior.

Conclusions:

  • Classical analogs derived from Wigner functions reveal system delocalization and correlations.
  • Entropy trends provide insights into the shared information and correlations within quantum and classical systems.
  • The study highlights how correlations, rather than entanglement itself, are reflected in entropy changes.