  Superconducting qubits are a leading candidate for quantum computing but
display temporal fluctuations in their energy relaxation times T1. This
introduces instabilities in multi-qubit device performance. Furthermore,
autocorrelation in these time fluctuations introduces challenges for obtaining
representative measures of T1 for process optimization and device screening.
These T1 fluctuations are often attributed to time varying coupling of the
qubit to defects, putative two level systems (TLSs). In this work, we develop a
technique to probe the spectral and temporal dynamics of T1 in single junction
transmons by repeated T1 measurements in the frequency vicinity of the bare
qubit transition, via the AC-Stark effect. Across 10 qubits, we observe strong
correlations between the mean T1 averaged over approximately nine months and a
snapshot of an equally weighted T1 average over the Stark shifted frequency
range. These observations are suggestive of an ergodic-like spectral diffusion
of TLSs dominating T1, and offer a promising path to more rapid T1
characterization for device screening and process optimization.
