Material losses characterization in superconducting resonators based on α and β Tantalum

Implementation of tantalum as a new material platform in transmon qubit has shown promising results with coherence time exceeding 0.3 ms[1]. To understand the underlying cause for record breaking coherence times, the main focus has been on use of alpha phase tantalum to achieve high quality qubits and resonators whereas the beta phase remains largely unexplored. In this work, we compare internal quality factor in lumped element resonators as a function of photon number and temperature. We use various material characterization tools to investigate surface and bulk properties of tantalum. Further, we vary the energy participation ratio in tantalum metal-substrate and metal-air interfaces to estimate the loss tangent and get insight into dominant loss mechanism.
[1] Place, A.P.M., Rodgers, L.V.H., Mundada, P. et al. Nat Commun 12, 1779 (2021).