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An Otto engine is a four-stroke engine that uses a mixture of gasoline and air as the working fuel. The fuel is injected into the cylinder, and the piston is moved completely down so that the cylinder is at maximum volume. By moving the piston up, adiabatic compression takes place. The spark plug ignites the gasoline-air mixture, and the burning fuel adds heat to the system at a constant volume. The heated mixture expands adiabatically and gets further cooled by exhausting heat, and this cyclic...
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Converting work to heat is an irreversible process, and the purpose of a heat engine is to reverse the effect partially. Heat engines aim to increase the efficiency of the reversal, that is, maximize the work retrieved from heat. If the efficiency of a heat engine were 100%, it would imply reversing the process completely without introducing any other effect. Thus, it would violate the second law of thermodynamics.
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The Carnot engine works between two heat reservoirs of fixed temperatures. The Carnot cycle begs the following question: Is it possible to devise a heat engine that is more efficient than a Carnot engine between two fixed temperatures? The answer lies in designing a Carnot refrigerator.
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The hypothetical Carnot cycle consists of an ideal gas subjected to two isothermal and two adiabatic processes. Since the internal energy of an ideal gas depends only on its temperature, which is the same before and after the completion of the Carnot cycle, there is no change in its internal energy. Hence, using the first law of thermodynamics, the total heat exchanged by the ideal gas equals the total work done. Thus, we can quantify the efficiency of the Carnot cycle via the heat exchanged...
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Operational Constraints in Quantum Otto Engines: Energy-Gap Modulation and Majorization.

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Large Scale Energy Efficient Sensor Network Routing Using a Quantum Processor Unit
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Quantum Heat Engines with Complex Working Media, Complete Otto Cycles and Heuristics.

Ramandeep S Johal1, Venu Mehta1

  • 1Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S.A.S. Nagar, Manauli PO 140306, Punjab, India.

Entropy (Basel, Switzerland)
|September 28, 2021
PubMed
Summary

This study explores quantum Otto engines using coupled spins, revealing performance conditions linked to majorization. The findings offer insights into quantum heat engine efficiency beyond classical limits.

Keywords:
Otto efficiencyXXX spin-modelcomplete Otto cycleheuristicsmajorizationquantum Otto cyclequantum heat enginequantum thermodynamics

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Area of Science:

  • Quantum thermodynamics
  • Quantum information science
  • Statistical mechanics

Background:

  • Quantum thermal machines leverage non-classical resources like interactions within the working medium.
  • Previous work showed Heisenberg exchange interaction enhances quantum Otto engine efficiency, with an upper bound tighter than Carnot efficiency.

Purpose of the Study:

  • To examine the performance of a quasi-static quantum Otto engine with two arbitrary-magnitude spins.
  • To determine the necessary conditions for engine performance and efficiency upper bounds for coupled spins.
  • To connect quantum heat engine performance with the concept of majorization.

Main Methods:

  • Analysis of extreme case scenarios for coupled and uncoupled spin models.
  • Formulation of heuristics to infer necessary performance conditions.
  • Investigation of complete Otto cycles within the average cycle.

Main Results:

  • Heuristics derived for necessary conditions governing engine performance.
  • Established a link between quantum heat engine performance and majorization.
  • Identified insights into average performance through the study of complete Otto cycles.

Conclusions:

  • The study provides a framework for understanding quantum Otto engine performance with arbitrary spin magnitudes.
  • The connection to majorization offers a new perspective on quantum thermodynamic resource theory.
  • The findings contribute to the development of more efficient quantum thermal devices.