Characterization of Magnetic and Infrared Radiation Shielding with High Quality Superconducting Microwave Resonators*

The quantitative characterization of different sources of decoherence is an important step in the optimization of superconducting circuits. Here we present a systematic study of the effect of shielding on CPW resonators and we find that magnetic shielding as well as shielding from IR radiation are both crucial to obtain internal quality factors (Qi) greater than five million in the single photon excitation regime. We investigate samples from different materials (Nb, TiN, Al) and probe the nature of the microwave-frequency loss by varying the power and the temperature, deducing the efficacy of the shielding in terms by way of the power spectral densities of Qi and the resonance frequency. We compare the performance of multiple shielding configurations involving Cryoperm 10, Metglas 2714A and Sn plated Cu coated with IR absorbing epoxy.