Ergotropic advantage in a measurement-fueled quantum heat engine

Area of Science:

• Quantum thermodynamics
• Quantum information science
• Statistical mechanics

Background:

• Existing quantum heat engines often rely on thermal reservoirs.
• Quantum measurements can be used as an alternative energy source.
• Previous models explored four-stroke cycles with quantum measurement apparatuses.

Purpose of the Study:

• To investigate a coupled two-qubits heat engine utilizing generalized spin component measurements.
• To introduce and analyze a novel five-stroke cycle incorporating an ergotropy-extracting stroke.
• To compare the performance of the five-stroke engine with existing four-stroke and three-stroke models.

Main Methods:

• Modeling a coupled two-qubits system as a heat engine.
• Implementing generalized measurements of spin components.
• Introducing an ergotropy-extracting stroke into a quantum cycle.
• Analyzing performance metrics for different measurement directions (z-z, x-x).

Main Results:

• The five-stroke engine with ergotropy extraction outperforms four-stroke and three-stroke counterparts.
• For z-z measurements, the ergotropic stroke enhances performance, with the three-stroke engine matching the five-stroke performance.
• For arbitrary working media and non-selective measurements, the five-stroke work output equals the sum of four-stroke and three-stroke outputs.

Conclusions:

• A five-stroke quantum heat engine utilizing generalized measurements and ergotropy extraction demonstrates superior performance.
• The choice of measurement direction and post-measurement state ordering significantly impacts engine performance.
• Ergotropy extraction is a viable strategy for enhancing quantum heat engine efficiency.