Characterizing and Mitigating Vortex Loss in Superconducting Microwave Resonators

High-quality-factor superconducting thin-film microwave resonators are essential for qubit and detector applications, thus, minimizing dissipation is critical. Stray magnetic fields in the device environment can lead to trapped vortices that contribute loss if trapped in regions of large microwave currents. We use an adiabatic demagnetization refrigerator to study vortex loss in aluminum resonators, both lumped-element kinetic inductance detectors and coplanar waveguides, cooled in magnetic fields of a few hundred microtesla and below. By characterizing devices with various configurations of flux-trapping holes patterned in the superconducting film, we compare the effect of flux trap placement on resonator loss.