Key Takeaways

Use these points as the practical Q3D learning summary for QClang users.

RLGC Matrices	R, L, G, C matrices from Q3D are the primary inputs to circuit Hamiltonian models. Even small parasitic entries shift qubit frequencies by 10–100 MHz.
Superconducting Regime	At 4K, Al and Nb become superconducting → R→0, (L_k) dominates. Normal-metal values from Q3D need T-dependent correction.
Surface Participation	SPR × tan δ controls T₁. Design rule: minimise p_MA below 5 ppm via thick metal, wider CPW gaps, and clean interfaces.
Derived Outputs	Ec, Ej, g, chi, ζ, Γ_P are all computed from Q3D matrices. Iterating Q3D → Hamiltonian → optimise is the standard qubit design loop.