Correlated Qubit Degradation Events and Their Physical Classification from Cloud Quantum Processor Telemetry

We analyze 10.4 million calibration measurements from three IBM Heron superconducting quantumprocessors and identify two physically distinct classes of correlated multi-qubit degradationevents using only routine cloud-accessible telemetry. A column-wise permutation test reveals statisticallysignificant excess of simultaneous T1 crashes (42.8× expected at ≥ 10 simultaneous,p < 0.0001), simultaneous T2 crashes (4.8× at ≥ 10, p < 0.001), and simultaneous CZ gate-errorspikes (23.4× at ≥ 20, p < 0.0001; excess reaching 15,000× at ≥ 30). All three signals replicateacross backends (Fisher combined p < 10−7). Classifying high-crash snapshots by which parametersdegrade reveals two event types: Type A events degrade T1, T2, and CZ gate fidelity simultaneously(Cohen’s d = −0.94 for crashed-qubit T2), consistent with quasiparticle poisoning from high-energyparticle impacts; Type B events degrade T2 alone without affecting T1 or gate errors, consistentwith correlated dephasing noise. Type B events recover more slowly than Type A, persisting overmultiple calibration cycles with the same qubits remaining affected. T1-only events are rare acrossbackends, consistent with the expectation that relaxation degradation typically accompanies dephasing.Different qubits crash each time (mean Jaccard similarity ≤ 0.04), and readout fidelityremains unaffected in both event types. These correlated events—previously detectable only withdedicated particle detectors—are identifiable, classifiable, and operationally actionable from existingcloud calibration data without hardware modification.