Two-dimensional Superconducting Multimode Resonators for Surface Loss Extraction

Recent advancements in superconducting qubit coherence times by switching to tantalum capacitors demonstrates that understanding and improving materials is indispensable toward creating quantum processors. Superconducting microwave resonators have been widely used to study the materials losses in superconducting circuits, especially losses due to interface dielectrics. However, demonstrated methods for surface loss extraction require processing steps that are not used in, and thus not representative of, state-of-the-art fabrication procedures. In this talk we present a set of two-dimensional multimode resonators on sapphire that can be used to extract interface dielectric losses locally and with small uncertainty. By using slotline mode and nested structures of conventional resonator geometries, we can obtain a well-conditioned participation ratio matrix for different modes that accurately identifies the most lossy interface. Our design can be used to guide improvements in qubit fabrication.