Identification and mitigation of conducting package losses for quantum superconducting devices

Low-loss superconducting rf devices are required when used for quantum computation. Here, we present a series of measurements and simulations showing that conducting losses in the packaging our resonator affect maximum achievable internal quality factors (Qi) thin-film Al quarter-wave resonators with fundamental resonant frequencies varying between 4.9 5.8 GHz. By utilizing different widths gaps, volumes stored electromagnetic energy were sampled, thus affecting Qi. When backside sapphire substrate device is adhered to Cu package silver glue, monotonic decrease Qi found as sampling volume increased. This result induced currents large surface resistance regions dissipation underneath substrate. placing hole using material package, Ohmic increase larger size resonators.