OpenFermion is an open-source Python package for compiling and analyzing quantum algorithms to simulate fermionic systems, including quantum chemistry. Among other features, it includes data structures and tools for obtaining and manipulating representations of fermionic and qubit Hamiltonians. More information can be found in the release paper.

Installing the latest stable OpenFermion requires the Python package installer pip. (Make sure that you are using an up-to-date version of it.)

Currently, OpenFermion is tested on Mac, Windows, and Linux. We recommend using Mac or Linux because the electronic structure plugins are only compatible on these platforms. However, for those who would like to use Windows, or for anyone having other difficulties with installing OpenFermion or its plugins, we provide instructions for creating and using a Docker image – see the docker/ subdirectory. The Docker image provides a virtual environment with OpenFermion and select plugins pre-installed. The Docker installation should run on any operating system where Docker can be used.

To install the latest PyPI release of OpenFermion as a Python package for the current user (which avoids modifying system Python packages), run the following command:

python -m pip install --user openfermion

To install the latest version of OpenFermion in development mode, run the following commands:

git clone https://github.com/quantumlib/OpenFermion cd OpenFermion python -m pip install -e .

OpenFermion relies on modular plugin packages for significant functionality. Specifically, plugins are used to simulate and compile quantum circuits and to perform classical electronic structure calculations. Follow the links below to learn more!

• OpenFermion-FQE is a high-performance emulator of fermionic quantum evolutions specified by a sequence of fermion operators, which can exploit fermionic symmetries such as spin and particle number.

• Forest-OpenFermion to support integration with Forest.
• SFOpenBoson to support integration with Strawberry Fields.

• OpenFermion-Psi4 to support integration with Psi4.
• OpenFermion-PySCF to support integration with PySCF.
• OpenFermion-Dirac to support integration with DIRAC.
• OpenFermion-QChem to support integration with Q-Chem.

Documentation for OpenFermion can be found at quantumai.google/openfermion and the following links:

• Installation
• API Docs
• Tutorials

You can run OpenFermion's interactive Jupyter Notebooks, such as the introductory tutorial, in Colab or MyBinder.

We'd love to accept your contributions and patches to OpenFermion. There are a few small guidelines you need to follow.

• Contributions to OpenFermion must be accompanied by a Contributor License Agreement (CLA). You (or your employer) retain the copyright to your contribution; the CLA simply gives us permission to use and redistribute your contributions as part of the OpenFermion project. Please visit https://cla.developers.google.com/ to see your current agreements on file or to sign a new one.
• All submissions, including submissions by project members, require review. We use GitHub pull requests for this purpose. Consult the appropriate GitHub Help documentation for more information on using pull requests.
• Please make sure your new code comes with extensive tests! We use automatic testing to make sure all pull requests pass tests and do not decrease overall test coverage by too much.
• Please also make sure to follow the OpenFermion source code style. We mostly follow Python's PEP 8 guidelines and use the corresponding linter to check for it.
• Code should always be accompanied by documentation. Formatted OpenFermion documentation is generated automatically and can be found on the Quantum AI web site.
• We use GitHub issues for tracking requests and bugs. Please post questions to the Quantum Computing Stack Exchange with an openfermion tag.

OpenFermion is the work of many people. When using OpenFermion for research projects, please cite the published paper:

Jarrod R McClean, Nicholas C Rubin, Kevin J Sung, Ian D Kivlichan, Xavier Bonet-Monroig, Yudong Cao, Chengyu Dai, E Schuyler Fried, Craig Gidney, Brendan Gimby, Pranav Gokhale, Thomas Häner, Tarini Hardikar, Vojtěch Havlíček, Oscar Higgott, Cupjin Huang, Josh Izaac, Zhang Jiang, Xinle Liu, Sam McArdle, Matthew Neeley, Thomas O'Brien, Bryan O'Gorman, Isil Ozfidan, Maxwell D Radin, Jhonathan Romero, Nicolas P D Sawaya, Bruno Senjean, Kanav Setia, Sukin Sim, Damian S Steiger, Mark Steudtner, Qiming Sun, Wei Sun, Daochen Wang, Fang Zhang, and Ryan Babbush. (2020). OpenFermion: The Electronic Structure Package for Quantum Computers. Quantum Science and Technology, 5(3), 034014.

For formatted citations and records in other formats, as well as records for all releases of OpenFermion past and present, please visit the OpenFermion page on Zenodo.

Ryan Babbush (Google), Jarrod McClean (Google), Nicholas Rubin (Google), Kevin Sung (University of Michigan), Ian Kivlichan (Harvard), Dave Bacon (Google), Xavier Bonet-Monroig (Leiden University), Yudong Cao (Harvard), Chengyu Dai (University of Michigan), E. Schuyler Fried (Harvard), Craig Gidney (Google), Brendan Gimby (University of Michigan), Pranav Gokhale (University of Chicago), Thomas Häner (ETH Zurich), Tarini Hardikar (Dartmouth), Vojtĕch Havlíček (Oxford), Oscar Higgott (University College London), Cupjin Huang (University of Michigan), Josh Izaac (Xanadu), Zhang Jiang (NASA), William Kirby (Tufts University), Xinle Liu (Google), Sam McArdle (Oxford), Matthew Neeley (Google), Thomas O'Brien (Leiden University), Bryan O'Gorman (UC Berkeley, NASA), Isil Ozfidan (D-Wave Systems), Max Radin (UC Santa Barbara), Jhonathan Romero (Harvard), Daniel Sank (Google), Nicolas Sawaya (Harvard), Bruno Senjean (Leiden University), Kanav Setia (Dartmouth), Hannah Sim (Harvard), Damian Steiger (ETH Zurich), Mark Steudtner (Leiden University), Qiming Sun (Caltech), Wei Sun (Google), Daochen Wang (River Lane Research), Chris Winkler (University of Chicago), Fang Zhang (University of Michigan), and Emiel Koridon (Leiden University).

We are happy to include future contributors as authors on later releases.

For any questions or concerns not addressed here, please email quantum-oss-maintainers@google.com.

This is not an officially-supported Google product. This project is not eligible for the Google Open Source Software Vulnerability Rewards Program.

Copyright 2017 The OpenFermion Developers.