Probing Micro-eV States at the Material Interfaces of Superconducting Devices

Micro-eV states in amorphous materials and at material interfaces have long plagued planar superconducting circuits. These states interfere with qubit lifetimes and often set the limit on resonator quality factors in the single photon regime. We propose a superconducting resonant circuit that enables characterization of these states for planar devices. Using a biased-bridge interdigitated capacitor circuit we apply a slow-varying (megahertz) electric field on the defect states and sweep their energies. We will discuss different experiments, including probes of energy distributions, dipole moments, and reaching the strong photon-µeV state coupling limit in these devices.