Lindbladian approach for many-qubit thermal machines: enhancing the performance with geometric heat pumping by interaction

TL;DR

This paper develops a Lindblad-based framework for analyzing many-qubit quantum thermal machines, highlighting geometric heat pumping effects and how interactions influence performance bounds.

Contribution

It introduces a systematic expansion approach that separates geometric and dissipative effects, providing explicit thermodynamic expressions and bounds for interacting qubit systems.

Findings

Geometric heat pumped per cycle is bounded by $k_B T N_q \\ln 2$ for non-interacting qubits.

Interactions and asymmetric couplings can surpass the geometric heat pumping bound.

Numerical analysis shows the impact of qubit interactions on dissipated power and performance.

Abstract

We present a detailed analysis of slowly driven quantum thermal machines based on interacting qubits within the framework of the Lindblad master equation. By implementing a systematic expansion in the driving rate, we derive explicit expressions for the rate of work of the driving forces, the heat currents exchanged with the reservoirs, and the entropy production up to second order, ensuring full thermodynamic consistency in the linear-response regime. The formalism naturally separates geometric and dissipative contributions, identified by a Berry curvature and a metric in parameter space, respectively. Analytical results show that the geometric heat pumped per cycle is bounded by $k_B T N_q \ln 2$ for $N_q$ non-interacting qubits, in direct analogy with the Landauer limit for entropy change. This bound can be surpassed when qubit interactions and asymmetric couplings to the baths are introduced. Numerical results for the interacting two-qubit system reveal a non-trivial role of the interaction between qubits and the coupling between the qubits and the baths in the behavior of the dissipated power. The approach provides a general platform for studying dissipation, pumping, and performance optimization in driven quantum devices operating as heat engines.