Strongly coupled quantum Otto cycle with single qubit bath

TL;DR

This paper models a quantum Otto cycle involving a single qubit bath, deriving exact dynamics that include non-Markovian effects, and provides analytical expressions for efficiency and power in various regimes.

Contribution

It introduces a strongly coupled two-qubit model with an exact master equation, extending thermodynamic analysis beyond weak coupling and deriving explicit performance metrics.

Findings

Exact master equation in GKLS form for specific parameters

Closed-form expressions for efficiency and power

Demonstrates non-Markovian effects in quantum thermodynamics

Abstract

We discuss a model of a closed quantum evolution of two-qubits where the joint Hamiltonian is so chosen that one of the qubits acts as a bath and thermalize the other qubit which is acting as the system. The corresponding exact master equation for the system is derived. Interestingly, for a specific choice of parameters the master equation takes the Gorini-Kossakowski-Lindblad-Sudarshan (GKLS) form with constant coefficients, representing pumping and damping of a single qubit system. Based on this model we construct an Otto cycle connected to a single qubit bath and study its thermodynamic properties. Our analysis goes beyond the conventional weak coupling scenario and illustrates the effects of finite bath including non-Markovianity. We find closed form expressions for efficiency (coefficient of performance), power (cooling power) for heat engine regime (refrigerator regime) for different modifications of the joint Hamiltonian.