Evaluating Qubit Coherence Statistics in the Presence of Time-Correlated Fluctuations*

Reducing loss in superconducting qubit circuits is critical for enabling the development of large-scale quantum computing architectures. This task is especially challenging in the face of variability resulting from device-to-device differences and fluctuating device properties. In this work, we investigate the T₁ statistics for set of 54 nominally identical, high-coherence transmon qubits (T₁, T₂ Ramsey, T₂ Echo ~ 100 µs) and use this large data set to study the scaling of the error in the ensemble mean T₁ estimate as a function of number of devices and sampling time. We then apply this knowledge to assess the statistical significance of weakly contributing loss mechanisms.