Bounds on nonequilibrium fluctuations for asymmetrically driven quantum Otto engines.

Area of Science:

• Quantum thermodynamics
• Statistical mechanics
• Nonequilibrium systems

Background:

• Quantum Otto engines offer a platform for studying fundamental thermodynamic principles.
• Understanding nonequilibrium fluctuations is crucial for characterizing engine performance and limitations.

Purpose of the Study:

• To investigate the bounds on nonequilibrium work and heat fluctuations in a four-stroke asymmetrically driven quantum Otto engine.
• To establish relations between work and heat fluctuations for hot and cold reservoirs.
• To connect these bounds with thermodynamic uncertainty relations.

Main Methods:

• Analysis of a quantum Otto engine model using a single qubit as the working medium.
• Derivation of strict relations between fluctuations of work and individual heat.
• Examination of bounds in both engine and refrigerator regimes.

Main Results:

• Identified strict relations between work and heat fluctuations for both hot and cold reservoirs.
• Demonstrated upper and lower bounds on the ratio of nonequilibrium fluctuations of output work to input heat.
• Established a hierarchical relation between relative fluctuations of work and heat, linking to thermodynamic uncertainty relations.

Conclusions:

• The derived bounds are fundamental consequences of considering forward and reverse engine cycles equally.
• The study extends these findings to parametrically driven harmonic oscillator Otto engines.
• These results provide insights into the fundamental limits of quantum heat engines and refrigerators.