QUICHE

QUICHE (QUantum Integrated CHEmistry) is a toolkit for studying quantum computing algorithms for quantum chemistry, with a focus on quantum phase estimation (QPE). It integrates a resource estimation backend based on Qualtran, with a QuEST-powered simulation backend. The two backends can be used in isolation or combined using the Python package capable of dispatching between the two.

⚠️ This project is in early active development and should not be considered production-ready. Breaking changes may occur without notice before v1.0.

Features

• Range of quantum phase estimation algorithms including various single- and multi-ancilla methods.
• Wide variety of Hamiltonian simulation techniques, such as Suzuki-Trotter, QDRIFT and qubitisation.
• Extensible, Python-based resource estimation tooling.
• High-performance simulation capabilities.

Installation

QUICHE is available on PyPI as pyquiche. For a basic install, execute

pip install pyquiche

Then import the package from Python

import quiche

Prebuilt wheels are available for Linux (x86_64, aarch64), macOS 15+ (arm64) and Windows (x64), on Python 3.12 or later. They bundle a multithreaded, double precision build of QuEST. On other platforms pip falls back to building from source. That is also needed for custom precision, GPU acceleration or MPI-enabled builds.

Building from source

Building from source compiles the C++ simulation backend locally. This requires CMake, a C++17 compiler and network access to fetch dependencies. MPI- and GPU-enabled builds additionally require the corresponding toolchains, which are not fetched automatically.

The simulation backend depends on:

• QuEST for simulation. Always built from a pinned source archive, since QUICHE depends on internal headers that are not part of the installed interface.
• nanobind for Python bindings. Toggled with QUICHE_BUILD_BINDINGS.
• Catch2 for testing. Toggled with QUICHE_BUILD_TESTS.

nanobind and Catch2 are located with find_package and downloaded via FetchContent if unavailable.

To build the Python package from the published sdist, passing configuration flags through to CMake:

pip install pyquiche --no-binary pyquiche -C cmake.define.ENABLE_DISTRIBUTION=ON

Note: --no-binary is required: without it pip installs the prebuilt wheel and the configuration flags are ignored.

Or to build from a checkout

git clone https://github.com/Quantum-Motion/quiche.git
cd quiche
pip install .

C++ backend only

To build only the C++ simulator backend, along with the examples, execute

cd quiche
cmake -B build -D QUICHE_BUILD_EXAMPLES=ON
cmake --build build

Then execute an example (e.g. the Textbook QPE example)

./build/cpp/examples/qpe-textbook

Other C++ configuration flags can be similarly toggled ON and OFF. See also the QuEST docs for the available simulation flags.

Usage

For Python usage examples see the python/examples directory. For C++ simulator usage examples see the cpp/examples directory.

Contributing

For further information about how you can contribute to QUICHE see the contributing guide.

License

Copyright 2026 Quantum Motion Technologies Ltd. Licensed under the Apache License, Version 2.0.

Funding

This software is supported by Innovate UK and Germany's ZIM via the QUantum-Integrated CHEmistry (QUICHE) project.