Thermodynamic Stability Metric Provides Early Warning of Qubit Degradation on IBM Quantum Hardware

We present empirical evidence that a thermodynamic stability metric Φ = I × ρ − α × S serves as a leading indicator of qubit degradation on IBM Quantum hardware. Analysis of 445 qubits across three backends (ibm_fez, ibm_marrakesh, ibm_torino) over 30 days demonstrates 100% detection rate against IBM-reported status transitions with average lead time of 163 hours (6.8 days) and maximum lead time of 480 hours (20 days). The coherence ratio ρ = T2/T1 accounts for 70–78% of component contribution in machine learning models, suggesting a substantially larger role for coherence information in stability monitoring than is reflected in prior qubit-selection heuristics. Cross-backend transfer achieves 98.4% balanced accuracy without retraining. These results establish Φ as an early warning indicator for quantum processor maintenance scheduling.