Modeling Parasitic Mode Coupling in Superconducting Qubits

Qubit coherence can be limited by parasitic couplings to spurious electromagnetic modes associated with the qubit chip structures and device packaging. A detailed understanding of these interactions is therefore critical for optimizing qubit performance. In this work, we use a combination of numerical and analytical approaches to derive an equivalent LC network model that captures the coupling of qubits to unwanted parasitic modes. We compare model results to experimental data from transmon qubit circuits.