Surface participation and dielectric loss in flipchip superconducting qubits

Superconducting transmon qubits are widely used for quantum information processing, however, these qubits are often limited by dielectric loss. To mitigate the losses in the transmon qubits, it has recently been proposed that hybrid qubits involving semiconductor-superconductor hybrids may enhance the lifetime of superconducting qubits. On the other hand, 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. In this work, we quantitatively extract surface dielectric dissipation in transmon qubit under flip-chip structure through experimental and numerical study and we draw conclusion for how these losses may impact future hybrid qubits.