Thermodynamics of local baths in the context of work extraction

TL;DR

This paper demonstrates that work can be extracted from locally thermal two-qubit systems with or without initial entanglement by using local and global unitaries in the presence of thermal baths at different temperatures, even after removing quantum correlations.

Contribution

It introduces a protocol for work extraction from locally thermal states with quantum entanglement or no entanglement, utilizing local and global unitaries with thermal baths at different temperatures.

Findings

Work can be extracted via local unitaries during entanglement removal.

Additional work can be extracted from the final product state using global unitaries.

Work extraction is possible even without initial entanglement.

Abstract

We consider locally thermal states (for two qubits) with certain amount of quantum entanglement present between them. Unlike previous protocols we show how work can be extracted by performing local unitary operations on this state by allowing those two qubits to interact with thermal baths of different temperatures, thereby gradually removing the entanglement between them till they reach a direct product state. Also we demonstrate that, further work can be extracted from this direct product state by performing global unitary operation, thereby establishing that work can be extracted from a system composed of locally thermal subsystems even after removing quantum correlations between them if the subsystems are thermalized at different temperatures. Also we show that even if we consider a initial state where there is no entanglement between the two qubits, we can also extract work locally using our method.