qpdk 0.4.0

QPDK is an open-source process design kit (PDK) for superconducting quantum RF applications built on 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 and 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+ 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).

Notable Components

QPDK ships with a broad set of ready-to-use superconducting circuit components. Browse all the components in the documentation.

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.

Quick Start

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()

# 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

Examples & Notebooks

• PDK cells in the documentation — Collection of all available geometries.
• qpdk/samples/ — Example layouts and simulations including qubit test chips, resonator arrays, routing demos, and 3D export.
• notebooks/ — Jupyter notebooks covering:
  • Resonator frequency modeling and S-parameter analysis
  • Circuit simulation with SAX
  • Monte Carlo fabrication tolerance analysis
  • Hamiltonian parameter extraction with scqubits
  • Pulse-level quantum gate simulation with QuTiP
  • Capacitor geometry optimization with Optuna
  • Dispersive shift calculation with Pymablock
  • Transmon design optimization with NetKet
• gsim example notebooks — Electromagnetic simulation examples using Palace and Meep with gdsfactory.

Installation

We recommend using uv for package management. just is used for project-specific recipes.

Installation for Users

Install the package with:

uv pip install qpdk

Or with pip:

pip install qpdk

Optional dependencies for the analytical models and simulation tools (SAX, scqubits, JAX) can be installed with:

uv pip install qpdk[models]

KLayout Technology Installation

To use the PDK in KLayout (for viewing GDS files with correct layers and technology settings), install the technology files:

python -m qpdk.install_tech

Installation for Contributors

For contributors, please follow the installation and development workflow instructions.

Project Structure

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)
• QPDK documentation (PDF)
• gdsfactory documentation

Contributing

We welcome contributions of all sizes: new components, improved models, bug fixes, documentation, and notebook tutorials. Please see the contributing guide to get started.

Support

For commercial support, training, and custom PDK development, please visit gdsfactory+ (gdsfactory.com/plus).

License

QPDK is released under the MIT License.