Losses of flipchip transmon and co-planar waveguide resonator

More and more hybrid qubits involving semiconductor-superconductor hybrids have been proposed through the past years. However, the integration into a transmon architecture may lead to additional losses from the semiconductor substrates which motivates the separation of high coherence superconducting circuit and the semiconductor into separate chips that are then combined galvanically using bump bond in a flip-chip architecture. Here, we present our fabrication flow for flip-chip device that include a seed-layer of gold to enable efficient and reproducible electroplating of Indium. We show experiment results of both transmon and co-planar waveguide resonators in a flipchip environment, and quantify the loss mechanism limited our devices.