Work extraction from long-lived quantum coherence of a three-level system

TL;DR

This paper investigates how long-lived quantum coherence in a three-level system can be harnessed as a resource for work extraction, proposing protocols that convert coherence into useful energy and analyzing their efficiency.

Contribution

It introduces novel thermodynamic protocols that convert quantum coherence into work, demonstrating maximal work extraction from coherence in a single-shot cycle.

Findings

Quantum coherence can be transformed into population asymmetry for work extraction.

The proposed protocol achieves maximal extractable work measured by free energy difference.

Long-lived coherence provides thermodynamic advantages for quantum thermal machines.

Abstract

We analyze work extraction protocols using the long-lived quantum coherence of a three-level quantum system, which is coupled to a thermal bath through dipole-monopole interactions. We identify situations where persistent quantum coherence arises, i.e., for systems with degenerate excited states with aligned transition dipoles or nearly degenerate systems with small energy splittings. By designing two innovative thermodynamic protocols involving energy-preserving unitary operations, we show that quantum coherence can be transformed into population asymmetry, serving as a quantum resource for work extraction. As the system approaches final thermal equilibrium, the initial quantum coherence effectively acts as fuel, being progressively consumed. Specifically, we propose an optimized protocol capable of extracting the maximal extractable work (MEW), measured by the free energy difference (FED), from quantum coherence in a single-shot thermodynamic cycle. Our results highlight the thermodynamic advantages of long-lived coherence in a three-level quantum system and could influence future designs of coherence-driven quantum thermal machines.