Reusable and Circuit-Structure-Preserving Error Mitigation for High-Fidelity Quantum Simulations

Accurately characterizing and mitigating the impact of noise is essential for improving the fidelity of quantum simulations on Noisy Intermediate-Scale Quantum (NISQ) devices. In this work, we introduce a circuit-structure-preserving error-mitigation framework designed for parameterized quantum circuits. Unlike conventional approaches that alter circuit topology or require heavy post-processing, our method preserves the native architecture while systematically diagnosing gate noise. This structure-preserving feature enables robust, high-fidelity simulations even in the presence of significant hardware noise, making the approach particularly effective for small-scale circuits executed at high sampling rates, such as those used in variational algorithms and quantum neural networks. To benchmark its performance, we apply the method to variational quantum simulations of a non-Hermitian ferromagnetic transverse-field Ising chain implemented on IBM Quantum processors. The mitigated results exhibit excellent agreement with exact theoretical predictions across a wide range of noise conditions. Thus, our framework provides a scalable and hardware-efficient strategy for the current hardware.