Simulation pathways

A Quantum Metal design reaches an electromagnetic solver along one of several paths. Which one to take depends on what you need to compute and what you can install. The tutorials use all of them, often on the same kind of device, so a result from one path can be checked against another.

Pathway

Computes

Install

Where in Metal

Tutorials

Ansys HFSS / Q3D (commercial)

eigenmodes and energy participation (EPR); driven S/Z/Y parameters; capacitance matrices for the lumped-oscillator model (LOM)

Ansys Electronics Desktop with a license; pip install "quantum-metal[ansys]"

renderers hfss, q3d, aedt_hfss, aedt_q3d; analyses.simulation (EigenmodeSim, LumpedElementsSim, ScatteringImpedanceSim); LOManalysis

3.3; 4.01–4.05; 4.11–4.18; 4.21–4.23; pyaedt multiplanar; A.4–A.7

gmsh + ElmerFEM (open source)

capacitance matrices (electrostatics) for LOM

pip install "quantum-metal[mesh]" plus the ElmerFEM binaries (ElmerGrid, ElmerSolver on PATH; see README_Open_FEM_Stack.md)

QGmshRenderer, QElmerRenderer

3.5; 4.19; A.4; the two-qubit cell of the 17-qubit chip

gmsh + scikit-fem (open source, pure Python)

eigenmodes with lumped junction inductors; EPR, avoided-crossing, induced-EMF and impedance-matrix couplings; port impedance matrices; capacitance matrices

pip install "quantum-metal[skfem]" pymetis (pymetis optional)

qiskit_metal.analyses.fem (the solver) and qiskit_metal.analyses.em.package_modes (the analytic models); not yet a renderer

4.41–4.45

AWS Palace via SQDMetal (open source)

eigenmodes, capacitance, driven and inductance studies on MPI; lumped and wave ports, EPR

SQDMetal (install from GitHub) and the Palace solver (MPI binary: build from source or a container). pypalace is another Palace toolkit with a Quantum Metal gmsh export.

SQDMetal takes a QDesign directly today. A native path — renderer_name="palace" in the simulation classes, built on QGmshRenderer — is being designed; see the RFC in sqdlab/SQDMetal#67

none in Quantum Metal yet; an end-to-end tutorial is part of the integration plan

Choosing a path

  • Eigenmodes, EPR, S-parameters, and an Ansys license: HFSS, the most complete path in Quantum Metal today.

  • Capacitance and LOM without a license: ElmerFEM for larger models (it runs in parallel and supports higher-order elements); the scikit-fem solver for small ones or where installing binaries is not possible.

  • Eigenmodes and couplings without a license: the scikit-fem solver, for cells and arrays of simple qubits. Tutorials 4.43–4.45 reproduce a published HFSS study of a 10 × 10 transmon array to within a few percent.

  • Large full-wave models, wave ports, losses, clusters: Palace, through SQDMetal today; natively once the integration above lands.

  • Teaching, Colab, continuous integration: the scikit-fem solver needs only pip.

What the open-source paths do not do yet

  • ElmerFEM is connected for electrostatics only; its eigenmode and electromagnetic-wave solvers are not wired into Quantum Metal yet.

  • The scikit-fem solver uses lowest-order elements and zero-thickness metal, handles metal islands and junction lines but not ground planes with cutouts or CPWs, and runs in one process (up to about a million unknowns).

  • Neither has wave ports or losses (Palace does).

Plans

The roadmap sections “Open FEM stack” and “Solver backends” describe how these paths are meant to meet in Quantum Metal: shared, solver-neutral abstractions in core (ports, mesh-size control, named physical groups, boundary conditions, net naming, and a declared list of what each backend supports) that ElmerFEM, the scikit-fem solver, Palace and — in principle — Ansys all read, reached from the same simulation classes by renderer name; and how solver results are tested. The Palace design is discussed in sqdlab/SQDMetal#67. Design notes for the scikit-fem solver: docs/architecture/open_fem_scikit_fem.md in the repository.