Time-Aligned Coherence Collapse and Readout Error Bursts in Superconducting Qubit Calibration Data.

Superconducting qubit performance is commonly assessed using snapshot calibration metrics such as coherence time (T2) and readout error probability. While useful for short-term characterization, such static representations obscure temporal structure present in long-term device operation. This technical note presents a time-resolved empirical analysis of publicly available calibration data from the IBM Quantum Athens superconducting quantum processor. By treating calibration records as a chronologically ordered time series, the analysis reveals recurring temporal alignment between abrupt coherence collapses and short-lived bursts of elevated readout error. The analysis is descriptive and model-agnostic by design. No microscopic noise sources, control mechanisms, or causal relationships are inferred. The observations are restricted to pre–error-correction behavior and are intended to document non-stationary, structured behavior that is obscured when calibration data are interpreted solely as static snapshots. These observations are relevant for scheduling, benchmarking, and any methodology that assumes stationary calibration parameters.