# QPDK — Superconducting Quantum Process Design Kit [](https://gdsfactory.github.io/quantum-rf-pdk/) [](https://github.com/gdsfactory/quantum-rf-pdk/actions/workflows/test.yml) [](https://github.com/gdsfactory/quantum-rf-pdk/actions/workflows/test.yml) [](https://gdsfactory.github.io/quantum-rf-pdk/) [](https://gdsfactory.github.io/quantum-rf-pdk/qpdk.pdf) [](https://mybinder.org/v2/gh/gdsfactory/quantum-rf-pdk/HEAD) [](https://pypi.org/p/qpdk) [](https://choosealicense.com/licenses/mit/) **QPDK** is an open-source process design kit (PDK) for superconducting quantum RF applications built on [gdsfactory](https://gdsfactory.github.io/gdsfactory/). It provides a library of parametric quantum circuit components (transmon qubits, CPW resonators, Josephson junctions, etc.), analytical S-parameter models, routing utilities, and test-chip examples. QPDK gives researchers, engineers, and students a scriptable, version-controlled foundation to go from concept to GDSII in minutes. ## Key Features - **Rich component library** — Transmons, fluxonium, unimon qubits, CPW resonators, interdigital capacitors, SQUID junctions, launchers, bump bonds, TSVs, and more. - **Parametric & composable** — Combine Python functions (`@gf.cell`) into hierarchical designs or define full chips in YAML. - **Analytical circuit models** — Fast, differentiable S-parameter simulations powered by [SAX](https://gdsfactory.github.io/sax/) and [JAX](https://github.com/jax-ml/jax). - **Automated routing** — CPW-aware routing strategies with auto-tapers for complex layouts. - **KLayout integration** — Layer definitions, technology files, and cross sections for immediate visual inspection. - **Regression-tested** — GDS regression tests, netlist checks, and model validation. - **Notebook-driven workflows** — Jupyter notebooks for frequency modeling, tolerance analysis, parameter extraction, pulse-level simulation, and optimization. - **[GDSFactory+](https://gdsfactory.com/plus/) integration** — Seamlessly design, verify, and validate chips with the enhanced commercial extension. Includes access to 43+ foundry PDKs, graphical layout and schematic editors directly in VSCode, an AI assistant, and comprehensive verification tools (DRC, LVS, Connectivity checks). See the [QPDK graphical workflow tutorial](https://gdsfactory.com/plus/v2/tutorial/design/graphical-workflow/design-quantum-rf/#explore-and-simulate-a-resonator). ## Notable Components QPDK ships with a broad set of ready-to-use superconducting circuit components. Browse all the components in the [documentation](https://gdsfactory.github.io/quantum-rf-pdk/cells.html). ### Qubits | Transmon | Fluxonium | |------------------------------------------|--------------------------------------------| | Double-pad capacitively shunted qubit | Superinductance-shunted qubit | |  |  | | Unimon | SQUID Junction | |--------------------------------------|------------------------------------------------| | Resonator-embedded junction qubit | Superconducting quantum interference device | |  |  | ### Passive Components | CPW Resonator | Interdigital Capacitor | |------------------------------------------------|---------------------------------------------------------| | Meandering coplanar waveguide resonator | Finger-style lumped-element capacitor | |  |  | ### Composite Components **Transmon with Resonator & Probeline** — Qubit cell with coupled resonator and probeline section:  ## Sample Test Chips QPDK includes some complete, tapeout-ready test chip examples that demonstrate real-world design workflows. ### Qubit Test Chip A four-transmon test chip with coupled readout resonators, probeline routing, flux lines, and launchers. Defined entirely in YAML.  ### Filled Qubit Test Chip The same qubit test chip with magnetic vortex trapping holes filling the ground plane and chip edges.  ### Flip-Chip (Flipmon) Test Chip A four-flipmon test chip demonstrating flip-chip qubit integration with coupled readout resonators, interdigital capacitor inputs, probeline routing, and flux lines — shown here with ground-plane filling and chip edges.  ### Resonator Test Chip A 16-resonator characterization chip with systematically varied CPW widths and gaps across two probelines. Ideal for extracting loss tangents and kinetic inductance. Also check [the notebook demonstrating network model simulations and fabrication tolerance Monte Carlo](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/monte_carlo_fabrication_tolerance.html).  ## Simulation Showcase QPDK comes with worked examples for circuit, quantum, and electromagnetic simulation. Every figure below is taken from one of the [example notebooks](https://gdsfactory.github.io/quantum-rf-pdk/notebooks.html) as rendered in the documentation. Click a title to open the full notebook. ### Circuit & Network Models | [Resonator Test Chip Transmission](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/monte_carlo_fabrication_tolerance.html) | [Fabrication Tolerance Monte Carlo](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/monte_carlo_fabrication_tolerance.html) | |------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------| | Both probelines of the 16-resonator chip, via SAX | Resonance spread from CPW width and gap variations | |  |  | ### Quantum Dynamics & Hamiltonians | [Flux-Tunable Transmon Spectrum](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/scqubits_parameter_calculation.html) | [Pulse-Level Gate Simulation](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/qutip_qip_pulse_simulation.html) | |-------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------| | Energy levels versus external flux with scQubits | X-gate populations and leakage in QuTiP-QIP | |  |  | | [Dispersive Shift](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/pymablock_dispersive_shift.html) | [Differentiable Transmon Optimization](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/circulax_transmon_optimization.html) | |-------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------| | Block-diagonalized dispersive shift with Pymablock | Circulax JAX gradients to target f and anharmonicity | |  |  | ### Electromagnetic Field Solvers | [COMSOL Resonator](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/comsol_cpw_resonator.html) | [HFSS Eigenmode](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/hfss_eigenmode_resonator.html) | [Elmer Capacitance](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/elmer_capacitance_interdigital.html) | |-------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------| | Driven E-field at resonance | Meandered CPW eigenmode field | IDC capacitance vs. FEM remeshing | |  |  |  | **[COMSOL Transmon Capacitance](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/comsol_qubit_capacitance.html)** — Electrostatic potential and field around the double-pad transmon:  The same workflows extend to [HFSS driven-modal](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/hfss_driven_capacitor.html) and [Q2D impedance](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/hfss_q2d_cpw_impedance.html) analyses, [Qucs-S model validation](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/model_comparison_to_qucs.html), and [NetKet](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/netket_transmon_design.html) and [Optuna](https://gdsfactory.github.io/quantum-rf-pdk/notebooks/optimize_capacitor_optuna.html) optimization. ## Quick Start ```python import gdsfactory as gf from qpdk import PDK PDK.activate() # Create a transmon qubit from qpdk.cells.transmon import double_pad_transmon qubit = double_pad_transmon(pad_size=(250, 400), pad_gap=15) qubit.plot() ``` ```python # Build a complete test chip from YAML from gdsfactory.read import from_yaml from qpdk import tech chip = from_yaml( "qpdk/samples/qubit_test_chip.pic.yml", routing_strategies=tech.routing_strategies, ) chip.show() # Opens in KLayout ``` ### Graphical Workflow with GDSFactory+ Prefer a visual workflow? QPDK runs in [GDSFactory+](https://gdsfactory.com/plus/), where you can place components in the schematic editor, inspect the layout, and run circuit simulations without leaving VSCode. The [Quantum-RF graphical workflow tutorial](https://gdsfactory.com/plus/v2/tutorial/design/graphical-workflow/design-quantum-rf/#explore-and-simulate-a-resonator) walks through exploring and simulating a resonator with QPDK step by step. ## Examples & Notebooks - **[PDK cells in the documentation](https://gdsfactory.github.io/quantum-rf-pdk/cells.html)** — Collection of all available geometries. - **[`qpdk/samples/`](https://github.com/gdsfactory/quantum-rf-pdk/tree/main/qpdk/samples)** — Example layouts and simulations including qubit test chips, resonator arrays, routing demos, and 3D export. - **[`notebooks/`](https://gdsfactory.github.io/quantum-rf-pdk/notebooks.html)** — Jupyter notebooks covering: - Resonator frequency modeling and S-parameter analysis - Circuit simulation with [SAX](https://github.com/flaport/sax) - Monte Carlo fabrication tolerance analysis - Hamiltonian parameter extraction with [scqubits](https://github.com/scqubits/scqubits) - Pulse-level quantum gate simulation with [QuTiP](https://qutip.org/) - Capacitor geometry optimization with [Optuna](https://optuna.org/) - Dispersive shift calculation with [Pymablock](https://pymablock.readthedocs.io/en/latest/) - Transmon design optimization with [NetKet](https://www.netket.org/) - **[GDSFactory+ Quantum-RF tutorial](https://gdsfactory.com/plus/v2/tutorial/design/graphical-workflow/design-quantum-rf/#explore-and-simulate-a-resonator)** — Graphical design and simulation of a resonator with QPDK in GDSFactory+. - **[gsim example notebooks](https://gdsfactory.github.io/gsim/)** — Electromagnetic simulation examples using Palace and Meep with gdsfactory. ## Installation We recommend using [`uv`](https://astral.sh/uv/) for package management. [`just`](https://github.com/casey/just) is used for project-specific recipes. ### Installation for Users Install the package with: ```bash uv pip install qpdk ``` Or with pip: ```bash pip install qpdk ``` Optional dependencies for the analytical models and simulation tools (SAX, scqubits, JAX) can be installed with: ```bash uv pip install "qpdk[models]" ``` `models` is one of several extras — `hfss`, `circulax`, `netket`, `pymablock`, `qutip`, `ray`, `scqubits` and `graphics` pull in the remaining simulation backends, and extras compose (`"qpdk[models,netket]"`). See [Installing optional extras](https://gdsfactory.github.io/quantum-rf-pdk/notebooks.html#installing-optional-extras) for what each one installs and which notebooks need it. ### KLayout Technology Installation To use the PDK in KLayout (for viewing GDS files with correct layers and technology settings), install the technology files: ```bash python -m qpdk.install_tech ``` #### NOTE After installation, restart KLayout to ensure the new technology appears. ### Installation for Contributors For contributors, please follow the [installation and development workflow instructions](https://gdsfactory.github.io/quantum-rf-pdk/contributing.html.md). ## Project Structure ```text quantum-rf-pdk/ ├── qpdk/ Core Python package │ ├── cells/ Component definitions (transmons, resonators, capacitors, …) │ ├── models/ Analytical models, mostly S-parameters │ ├── samples/ Example layouts and complete test chips │ ├── klayout/ KLayout technology files │ └── tech.py Layer stack, cross sections, routing strategies ├── tests/ Regression, integration and unit tests ├── notebooks/ Jupyter notebooks for design and simulation workflows └── docs/ Sphinx documentation (HTML + PDF) ``` ## Documentation - [QPDK documentation (HTML)](https://gdsfactory.github.io/quantum-rf-pdk/) - [QPDK documentation (PDF)](https://gdsfactory.github.io/quantum-rf-pdk/qpdk.pdf) - [gdsfactory documentation](https://gdsfactory.github.io/gdsfactory/) ## Contributing We welcome contributions of all sizes: new components, improved models, bug fixes, documentation, and notebook tutorials. Please see the [contributing guide](https://gdsfactory.github.io/quantum-rf-pdk/contributing.html.md) to get started. To build a PDK for your own fabrication process on top of QPDK, see [Customizing QPDK for Your Process](https://gdsfactory.github.io/quantum-rf-pdk/customizing.html.md). ## Support For commercial support, training, and custom PDK development, please visit [gdsfactory+ (gdsfactory.com/plus)](https://gdsfactory.com/plus/). ## License QPDK is released under the [MIT License](https://github.com/gdsfactory/quantum-rf-pdk/blob/main/LICENSE).