Microwave vortex dynamics in superconducting granular aluminum resonators

The high kinetic inductance of granular aluminum resonators presents a novel regime for studying vortex dynamics in superconductors. Vortices are quantized bundles of magnetic flux that penetrate through a superconductor for sufficiently large magnetic fields. Vortices trapped in regions of large microwave currents typically contribute excess loss for superconducting resonators and qubits. However, in highly disordered films, such as granular aluminum, we observe an anomalously low microwave loss due to vortices. We measure granular aluminum resonators at different magnetic field strengths, resonator frequencies, and temperature. We compare the vortex response in this system with that in more conventional superconducting films.