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  • Open Access

Quantum Otto engine with field-decoupled idle levels in a non-Hermitian XY model

Maimaitiyiming Tusun* and Fang Zhao†

  • Xinjiang Key Laboratory of Luminescent Minerals and Optical Functional Materials, School of Physics and Electronic Engineering, Xinjiang Normal University, Urumqi 830054, China

  • *Contact author: hawk@xjnu.edu.cn
  • †Contact author: gluons@foxmail.com
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APS Open Sci. 1, 000154 – Published 29 September, 2026

DOI: https://doi.org/10.1103/vf26-wl4f

Abstract

We propose a microscopic realization of the idle-level quantum heat engine architecture based on a two-qubit non-Hermitian XY model with a staggered imaginary magnetic field. The energy spectrum naturally separates into two working levels coupled to the external field and two field-decoupled idle levels entirely independent of it. Tuning the non-Hermitian parameter drives the system from a dissipative accelerator regime into a genuine heat engine regime, while simultaneously enhancing both the net work output and the cycle efficiency. The efficiency enhancement originates from the compression of the idle-level gap, which redistributes level occupations and progressively suppresses the idle-level heat current, signaling the approach to the reverse heat-flow regime that underlies the idle-level engine principle. We map the full thermodynamic phase diagram identifying engine, refrigerator, accelerator, and heater regimes, and decompose the heat current into working-level and idle-level contributions to clarify the microscopic origin of the performance gain. The model is implementable in trapped-ion and NMR quantum simulators. These results establish non-Hermiticity as a versatile control knob for idle-level quantum thermal machines.

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APS Open Sci. 1, 000154– Published 29 September, 2026
Vol. 1
  • Received 25 May 2026
  • Revised 2 August 2026
  • Accepted 21 September 2026
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