Non-Invasive 64-Qubit Diagnostic System with Decreasing Scaling Law: TRUE Zigzag Protocol on IBM Quantum Hardware

We report the first experimental validation of a scalable, non-invasive quantum processor diagnostic system at 64-qubit scale. The TRUE Zigzag protocol characterizes T1 and T2 coherence properties of all target qubits simultaneously within a single job execution, producing a complete qubit health map from only three job submissions. Tested on IBM Quantum's ibm_fez backend (8,192 shots), the system graded all 64 qubits from EXCELLENT to UNSTABLE with baseline-to-after stability of 0.985→0.985, confirming non-invasive operation. Central discovery — Decreasing Scaling Law: Average diagnostic disturbance measured 0.252% at 8 qubits, 0.146% at 32 qubits, and 0.148% at 64 qubits, representing 92.7% improvement over linear scaling predictions. The 64Q/32Q ratio of 1.01× demonstrates plateau behavior, indicating no accuracy loss at arbitrarily larger scales. All three IBM Quantum Job IDs are publicly disclosed for independent verification. Full per-qubit data (CSV), experimental metadata (JSON), and visualization (PNG) are included. Patent: KR 10-2025-0180416