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

Abstract:We study a quantum Otto heat engine whose working substance is an anisotropic two-qubit Heisenberg XYZ model. Independent local magnetic fields are used to control each spin individually. The influence of the longitudinal coupling, anisotropy, transverse coupling, and local fields on the net work output and efficiency is systematically examined. Reducing the longitudinal coupling is found to markedly improve both the maximum work and the peak efficiency. The engine performance reaches an optimum at a particular value of the anisotropy parameter. A local work analysis clarifies how work is produced during the cycle. Because of the asymmetric local fields and the intrinsic spin-spin interaction, the two qubits play markedly different thermodynamic roles; the interaction term itself contributes crucially to the total work. We further analyze the variation of quantum entanglement, quantified by concurrence, along the cycle. The results indicate that a pronounced change in entanglement between the hot and cold isomagnetic strokes is closely correlated with the efficiency enhancement. This work offers new insight into the operating principles and control of quantum Otto heat engines.

28 pages, 8 figures. All numerical calculations, symbolic verifications, and figure generation were performed using open-source Python libraries (NumPy, SciPy, Matplotlib). No proprietary commercial software was used in the production of this work. The complete Python source code is available from the corresponding author upon reasonable request

arXiv:2606.12877 [quant-ph]

(or arXiv:2606.12877v2 [quant-ph] for this version)