Coherence of Superconducting Whispering Gallery Resonators

Quantum signal processing applications rely on the design of microwave resonators with quality factors at the single photon level exceeding a million. We present a novel on-chip whispering gallery mode resonator formed by two superconducting rings on separate wafers facing each other. The mode energy is principally housed in the lossless vacuum between the rings. We measure internal quality factors of a few million at the single photon level. The superconducting whispering gallery resonator is easily integrable with superconducting qubits. It also constitutes a new tool to characterize thin film material properties.