Key Takeaways
=============

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

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   * - **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.