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Related Concept Videos

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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 models, the...
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A change in the internal energy of a system depends on the the net heat transfer into the system and the net work done by the system. The first law of thermodynamics, which is a generalized form of energy conservation, relates these three quantities mathematically. It states that the change in the internal energy equals the difference between the heat transfer and work done by the system.
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Energy additivity as a requirement for universal quantum thermodynamical frameworks.

Luis Rodrigo Neves1, Frederico Brito2,3

  • 1Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brasil. rodrigoneves@usp.br.

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Summary

A new framework for quantum thermodynamics proposes that internal energy must include environmental effects for consistency. This research reveals that internal energies in a two-qubit model are neither additive nor conservative, highlighting potential unphysical features.

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Area of Science:

  • Quantum Thermodynamics
  • Statistical Mechanics
  • Quantum Information Theory

Background:

  • Developing a universal thermodynamic framework for strongly coupled quantum systems is challenging.
  • Existing definitions of internal energy often neglect environmental interactions, leading to inconsistencies.
  • Autonomous quantum systems require a generalized approach to thermodynamics.

Purpose of the Study:

  • To propose a universal definition of internal energy that accounts for environmental interactions.
  • To establish a rigorous framework for energy additivity in quantum systems.
  • To investigate the properties of internal energy in a specific two-qubit quantum universe model.

Main Methods:

  • Introduction of an abstract framework for effective Hamiltonian-based approaches.
  • Definition of weak and strong forms of energy additivity.
  • Analysis of a two-qubit quantum universe model using the minimal dissipation approach.
  • Derivation of exact master equations and calculation of effective Hamiltonians and internal energies.

Main Results:

  • Internal energies in the two-qubit model are shown to be neither additive nor conservative.
  • The proposed framework allows for a consistent definition of internal energy, including environmental effects.
  • The study identifies unphysical features arising from non-additive and non-conservative internal energies.

Conclusions:

  • A universal notion of internal energy in quantum thermodynamics must incorporate environmental contributions.
  • The minimal dissipation approach reveals non-physical characteristics in simple quantum systems.
  • Further research is needed to refine thermodynamic frameworks for complex quantum systems.