Reduced Longitudinal Coupling Boosts Efficiency in Two-Qubit Quantum Otto Heat Engine

Reducing longitudinal coupling markedly improves both the maximum work output and peak efficiency in a quantum Otto heat engine powered by an anisotropic two-qubit Heisenberg XYZ model, according to a study published in Quantum Information Processing.

In the investigated engine, independent local magnetic fields are used to control each spin individually. The authors systematically examined the influence of longitudinal coupling, anisotropy, transverse coupling, and local fields on the net work output and efficiency.

Beyond the enhancements observed when reducing longitudinal coupling, the performance of the heat engine reaches an optimum at a particular value of the anisotropy parameter.

A local work analysis clarifies how work is produced during the cycle, revealing that the two qubits play markedly different thermodynamic roles because of the asymmetric local fields and the intrinsic spin–spin interaction.

The evaluation demonstrates that the intrinsic spin–spin interaction term itself contributes crucially to the total work generated during the engine cycle.

The study further analyzed the variation of quantum entanglement, quantified by concurrence, along the cycle, finding that a pronounced change in entanglement between the hot and cold isomagnetic strokes is closely correlated with efficiency enhancement.

According to the researchers, the study offers new insight into the operating principles and control of quantum Otto heat engines.

Subject of Research: Quantum Otto heat engine performance in an anisotropic Heisenberg XYZ model

Article Title: Quantum Otto engine powered by an anisotropic Heisenberg XYZ model under independent local magnetic fields

Article References: Li, M., Tusun, M., Zhao, F., Abudoula, H., & Wei, T. (2026). Quantum Otto engine powered by an anisotropic Heisenberg XYZ model under independent local magnetic fields. Quantum Information Processing, 25(11), Article 367. https://doi.org/10.1007/s11128-026-05385-w

Image Credits: AI Generated

DOI: 10.1007/s11128-026-05385-w

Keywords: quantum Otto engine, Heisenberg XYZ model, two-qubit system, anisotropic coupling, longitudinal coupling, transverse coupling, independent local magnetic fields, quantum thermodynamics, net work output, peak efficiency, local work analysis, spin-spin interaction, quantum entanglement, concurrence, isomagnetic strokes, asymmetric local fields, efficiency enhancement