Investigation into Charge Noise in a Tantalum Transmon on Sapphire Substrate across Higher Energy Levels*

Tantalum has recently emerged as a promising material for superconducting qubit fabrication. Transmon qubits constructed out of this metal can possess energy relaxation times greater than 300 µs and as such present an attractive platform for noise studies in higher energy levels. Here we present interwoven measurements of qubit spectroscopy, Ramsey decays, energy relaxation, and Echo decays across the low-lying one and two photon transitions. By observing the charge offset as a function of time, we validate the connection between charge dispersion present in qubit spectroscopy and Ramsey measurements, both in a single transition and across levels. In addition, we observe that discrete jumps in the charge offset dominate the long time charge dynamics, suggesting the charge environment fluctuates between a few metastable states. Finally, we observe occasional events of frequency instability that affect only one charge parity band but across multiple levels. We interpret these occurrences as a charge-parity dependent fluctuation of Josephson junction properties as opposed to a resonant Two-Level System interaction.