Paper 13 - Cross-Device and Cross-Temperature Noise Structure in Variational Gibbs-State Preparation: A Full-Tomography Held-Out Reanalysis

Overview This study investigates how quantum noise affects variational Gibbs-state preparation on trapped-ion quantum computers. What Was Analyzed The analysis uses full two-qubit tomography instead of relying only on a single quantity such as fidelity or effective temperature. It compares complete quantum states across different field settings, three trapped-ion devices, and two temperature regimes. Noise Models Compared Several noise descriptions are tested, including scalar depolarization, Pauli-channel models, coherent-error corrections, and generalized amplitude damping (GAD). Predictive Testing The models are trained on selected conditions and then tested on unseen conditions without refitting. This allows the analysis to measure whether a noise model remains useful outside the data used to fit it. Main Result A shared GAD-based model shows the most stable predictive behaviour across the tested devices and temperatures. In the strongest frozen cross-temperature test, parameters fitted at beta = 5 are applied directly at beta = 1 without refitting. The model: improves all 9 of 9 QPU cases reduces mean Hilbert-Schmidt distance from 0.08644669 to 0.07277861 gives a 15.81% reduction in mean error Interpretation The results support a shared damping-like noise-model family within the tested system. However, the fitted parameters are not universal, and the study does not claim a unique microscopic noise mechanism, universal hardware-noise parameters, retrocausality, or a universal physical law. Reproducibility The calculations are also implemented in QDL Research Suite v1.9.0, allowing the main numerical results to be reproduced and independently checked. Software DOI: 10.5281/zenodo.23181558