qiskit

Qiskit Metal: quarter-wave CPW resonator

A superconducting readout resonator (lambda/4 coplanar waveguide) capacitively coupled to a feedline, laid out with Qiskit Metal. The resonator length is computed from a target frequency, so changing the frequency re-generates the layout.

qiskit-metal-resonator/
├── environment.yml     conda env with the version pins qiskit-metal needs
├── src/
│   ├── analysis.py     analytic CPW model: impedance, eps_eff, lambda/4 length <-> frequency, lumped LC
│   └── resonator.py    builds the layout, exports GDS + a PNG preview (or opens the GUI)
├── tests/              pytest checks for analysis.py
└── output/             generated resonator.gds / resonator.png (git-ignored)

Run

conda env create -f environment.yml && conda activate qmetal
python src/resonator.py --freq 6.5          # writes output/resonator.gds and .png
python src/resonator.py --freq 7.0 --gui    # interactive Qt GUI (needs a display)
pytest tests

Defaults: 6.5 GHz, 10 um centre conductor / 6 um gap (~51 ohm on silicon), 9 x 6 mm chip.

How the length is chosen

eps_eff = (1 + eps_r)/2 (thick silicon substrate, eps_r = 11.45), so v = c/sqrt(eps_eff) and l = v / (4 f), about 4.62 mm at 6.5 GHz. The coupler tee’s own arm is subtracted from the meander length. The routed length is printed as routed_meander_um.

Limits of this model

The estimate ignores kinetic inductance, metal thickness and the loading from the coupler and the open end, so the real frequency will sit a little below the target. Verify and tune with an eigenmode simulation (Ansys HFSS through qiskit_metal.analyses) or a Sonnet sweep before fabrication.

Next steps