Note
This page was generated from tut/full-design-examples/Reference-design-1-Transmon-with-readout-resonator.ipynb.
Reference design 1 — Transmon with readout resonator¶
Build the canonical superconducting-qubit unit cell: one fixed-frequency transmon dispersively coupled to a meandered lambda/4 readout resonator on a shared coplanar-waveguide feedline.
Reference design — attribution. Adapted, with attribution, from the open-source SQDMetal project (Apache-2.0) and its benchmark devices in D. Sommers, P. Pakkiam, Z. Degnan, C.-C. Chiu, D. Gautam, Y.-H. Chen, and A. Fedorov, “Open-Source Highly Parallel Electromagnetic Simulations for Superconducting Circuits,” arXiv:2511.01220 (2025). Re-implemented here with stock Quantum Metal components.
[1]:
# In Colab / Binder, uncomment to install Quantum Metal (lite, no Qt):
# !pip install -q quantum-metal
[2]:
import qiskit_metal as qm
from qiskit_metal import Dict, designs
from qiskit_metal.qlibrary.qubits.transmon_pocket import TransmonPocket
from qiskit_metal.qlibrary.tlines.meandered import RouteMeander
from qiskit_metal.qlibrary.tlines.pathfinder import RoutePathfinder
from qiskit_metal.qlibrary.couplers.coupled_line_tee import CoupledLineTee
from qiskit_metal.qlibrary.terminations.launchpad_wb import LaunchpadWirebond
design = designs.DesignPlanar()
design.overwrite_enabled = True
09:27PM 15s INFO [_start_renderers]: Renderer=gmsh skipped: runtime dependency not installed (renderer_gmsh requires gmsh. Install with: pip install 'quantum-metal[mesh]' (or the legacy alias 'quantum-metal[fem]')).
1. The transmon qubit¶
A single TransmonPocket with one readout connection pad on its top-right corner.
[3]:
TransmonPocket(
design,
"Q1",
options=dict(
pos_x="0mm",
pos_y="-1.5mm",
pad_width="425um",
pocket_height="650um",
connection_pads=dict(readout=dict(loc_W=+1, loc_H=+1)),
),
)
[3]:
name: Q1
class: TransmonPocket
options:
'pos_x' : '0mm',
'pos_y' : '-1.5mm',
'orientation' : '0.0',
'chip' : 'main',
'layer' : '1',
'connection_pads' : {
'readout' : {
'pad_gap' : '15um',
'pad_width' : '125um',
'pad_height' : '30um',
'pad_cpw_shift' : '5um',
'pad_cpw_extent' : '25um',
'cpw_width' : 'cpw_width',
'cpw_gap' : 'cpw_gap',
'cpw_extend' : '100um',
'pocket_extent' : '5um',
'pocket_rise' : '65um',
'loc_W' : 1,
'loc_H' : 1,
},
},
'pad_gap' : '30um',
'inductor_width' : '20um',
'pad_width' : '425um',
'pad_height' : '90um',
'pocket_width' : '650um',
'pocket_height' : '650um',
'hfss_wire_bonds' : False,
'q3d_wire_bonds' : False,
'aedt_q3d_wire_bonds': False,
'aedt_hfss_wire_bonds': False,
'hfss_inductance' : '10nH',
'hfss_capacitance' : 0,
'hfss_resistance' : 0,
'hfss_mesh_kw_jj' : 7e-06,
'q3d_inductance' : '10nH',
'q3d_capacitance' : 0,
'q3d_resistance' : 0,
'q3d_mesh_kw_jj' : 7e-06,
'gds_cell_name' : 'my_other_junction',
'aedt_q3d_inductance': 1e-08,
'aedt_q3d_capacitance': 0,
'aedt_hfss_inductance': 1e-08,
'aedt_hfss_capacitance': 0,
module: qiskit_metal.qlibrary.qubits.transmon_pocket
id: 1
2. Feedline + readout resonator¶
A coplanar feedline runs between two wirebond launchpads through a coupled-line tee, which capacitively taps off a meandered lambda/4 resonator down to the qubit. total_length sets the resonator frequency.
[4]:
CoupledLineTee(
design,
"clt",
options=dict(
pos_x="0mm",
pos_y="1.5mm",
coupling_length="350um",
down_length="300um",
fillet="90um",
open_termination=False,
),
)
LaunchpadWirebond(
design, "LP1", options=dict(pos_x="-4mm", pos_y="1.5mm", orientation="0")
)
LaunchpadWirebond(
design, "LP2", options=dict(pos_x="4mm", pos_y="1.5mm", orientation="180")
)
RoutePathfinder(
design,
"feed_L",
options=dict(
fillet="90um",
pin_inputs=Dict(
start_pin=Dict(component="LP1", pin="tie"),
end_pin=Dict(component="clt", pin="prime_start"),
),
),
)
RoutePathfinder(
design,
"feed_R",
options=dict(
fillet="90um",
pin_inputs=Dict(
start_pin=Dict(component="clt", pin="prime_end"),
end_pin=Dict(component="LP2", pin="tie"),
),
),
)
RouteMeander(
design,
"readout_res",
options=dict(
fillet="90um",
total_length="7mm",
lead=Dict(start_straight="100um", end_straight="100um"),
pin_inputs=Dict(
start_pin=Dict(component="clt", pin="second_end"),
end_pin=Dict(component="Q1", pin="readout"),
),
),
)
[4]:
name: readout_res
class: RouteMeander
options:
'chip' : 'main',
'layer' : '1',
'pin_inputs' : {
'start_pin' : {
'component' : 'clt',
'pin' : 'second_end',
},
'end_pin' : {
'component' : 'Q1',
'pin' : 'readout',
},
},
'fillet' : '90um',
'lead' : {
'start_straight' : '100um',
'end_straight' : '100um',
'start_jogged_extension': '',
'end_jogged_extension': '',
},
'total_length' : '7mm',
'trace_width' : 'cpw_width',
'meander' : {
'spacing' : '200um',
'asymmetry' : '0um',
},
'snap' : 'true',
'prevent_short_edges': 'true',
'hfss_wire_bonds' : False,
'q3d_wire_bonds' : False,
'aedt_q3d_wire_bonds': False,
'aedt_hfss_wire_bonds': False,
'trace_gap' : 'cpw_gap',
'_actual_length' : '7.000000000000003 mm',
module: qiskit_metal.qlibrary.tlines.meandered
id: 7
3. Visualize¶
Next steps¶
Inspect the design tree:
design.components.keys()anddesign.qgeometry.tables.Export GDS for fabrication:
design.renderers.gds.export_to_gds('chip.gds')(Quantum Metal uses the moderngdstkbackend).Simulate: render to Ansys HFSS/Q3D (the validation gold standard) or to the open-source FEM path (Gmsh + Elmer today; AWS Palace on the roadmap) to extract eigenmodes, Q, and the capacitance matrix.
Tweak: every dimension above is a parameter — change
total_lengthto retune resonator frequencies, orpos_x/pos_yto relayout.
[5]:
design.components.keys()
[5]:
['Q1', 'clt', 'LP1', 'LP2', 'feed_L', 'feed_R', 'readout_res']
[6]:
fig = qm.view(design)
qm.show_inline(fig)
For more information, review the Introduction to Quantum Computing and Quantum Hardware lectures below
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Lecture Video | Lecture Notes | Lab |
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Lecture Video | Lecture Notes | Lab |
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Lecture Video | Lecture Notes | Lab |
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Lecture Video | Lecture Notes | Lab |
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Lecture Video | Lecture Notes | Lab |
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Lecture Video | Lecture Notes | Lab |