Comparative Coherence Decay of GHZ, W, and Product States Under Idle Noise in IBM Heron Quantum Processors: Extended Analysis with Dynamical Decoupling

Version 2. 1: Extended experimental analysis comparing coherence decay of GHZ, W, and product states on IBM Heron quantum processors (r1, r2, r3). Key findings: - GHZ states decay 2. 4–13. 8× slower than product states across three processor generations- Dynamical decoupling with virtual Z-pulses (DD-Z) provides marginal improvement (+0. 6%), while physical X-pulses (DD-X) degrade coherence by -24. 4%- W-state performance is architecture-dependent: superior on r1/r3, inferior on r2- Weak non-Markovian noise signatures detected at 5 µs delay window This version extends v1. 0 (DOI: 10. 5281/zenodo. 18274447) with W-state analysis, comprehensive DD protocol testing, and the DD-Z vs DD-X discovery. Backends: ibmₜorino (r1), ibmfez (r2), ibmboston (r3) Configuration: 3-5 qubits, 4000 shots, delays 0-100, 000 dt