Fix #1137 and #908: replace README.rst with Markdown version & update content (#1143)

This replaces the reStructuredText version of the README file with a
Markdown version, for better compatibility with our practices in our
other repos. In addition, it removes the OpenFermion logo to follow the
updated branding guidelines for Quantum AI. It also slightly reorganizes
the content, as well as provides a BibTeX version of the citation info,
and finally, adds the standard Google disclaimer and our QAI logo at the
bottom.

Author: mhucka

README.md

@@ -0,0 +1,213 @@
+<div align="center">
+
+# OpenFermion
+
+Electronic structure package for quantum computers.
+
+[![Compatible with Python versions 3.10 and higher](https://img.shields.io/badge/Python-3.10+-fcbc2c.svg?style=flat-square&logo=python&logoColor=white)](https://www.python.org/downloads/)
+[![Licensed under the Apache 2.0 license](https://img.shields.io/badge/License-Apache%202.0-3c60b1.svg?logo=opensourceinitiative&logoColor=white&style=flat-square)](https://github.com/quantumlib/OpenFermion/blob/main/LICENSE)
+[![OpenFermion project on PyPI](https://img.shields.io/pypi/v/OpenFermion.svg?logo=semantic-release&logoColor=white&label=Release&style=flat-square&color=fcbc2c)](https://pypi.org/project/OpenFermion)
+[![OpenFermion downloads per month from PyPI](https://img.shields.io/pypi/dm/openfermion?logo=PyPI&color=d56420&logoColor=white&style=flat-square&label=Downloads)](https://img.shields.io/pypi/dm/OpenFermion)
+
+[Features](#features) &ndash;
+[Installation](#installation) &ndash;
+[Plugins](#plugins) &ndash;
+[Documentation](#documentation) &ndash;
+[Contributing](#contributing-to-openfermion) &ndash;
+[Citing](#citing-openfermion) &ndash;
+[Authors](#authors) &ndash;
+[Contact](#contact)
+
+</div>
+
+## Features
+
+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](https://arxiv.org/abs/1710.07629).
+
+## Installation
+
+Installing the latest **stable** OpenFermion requires the Python package installer
+[pip](https://pip.pypa.io). (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/`](https://github.com/quantumlib/OpenFermion/tree/main/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.
+
+### User installation
+
+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:
+
+```shell
+python -m pip install --user openfermion
+```
+
+### Developer installation
+
+To install the latest version of OpenFermion in development mode, run the following commands:
+
+```shell
+git clone https://github.com/quantumlib/OpenFermion
+cd OpenFermion
+python -m pip install -e .
+```
+
+## Plugins
+
+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!
+
+### High-performance simulators
+
+*   [OpenFermion-FQE](https://github.com/quantumlib/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.
+
+### Circuit compilation plugins
+
+*   [Forest-OpenFermion](https://github.com/rigetticomputing/forestopenfermion) to support
+    integration with [Forest](https://www.rigetti.com/forest).
+*   [SFOpenBoson](https://github.com/XanaduAI/SFOpenBoson) to support integration with [Strawberry
+    Fields](https://github.com/XanaduAI/strawberryfields).
+
+### Electronic structure package plugins
+
+*   [OpenFermion-Psi4](http://github.com/quantumlib/OpenFermion-Psi4) to support integration with
+    [Psi4](http://psicode.org).
+*   [OpenFermion-PySCF](http://github.com/quantumlib/OpenFermion-PySCF) to support integration with
+    [PySCF](https://github.com/sunqm/pyscf).
+*   [OpenFermion-Dirac](https://github.com/bsenjean/Openfermion-Dirac) to support integration with
+    [DIRAC](http://diracprogram.org/doku.php).
+*   [OpenFermion-QChem](https://github.com/qchemsoftware/OpenFermion-QChem) to support integration
+    with [Q-Chem](https://www.q-chem.com).
+
+## Documentation
+
+Documentation for OpenFermion can be found at
+[quantumai.google/openfermion](https://quantumai.google/openfermion) and the following links:
+
+*   [Installation](https://quantumai.google/openfermion/install)
+*   [API Docs](https://quantumai.google/reference/python/openfermion/all_symbols)
+*   [Tutorials](https://quantumai.google/openfermion/tutorials/intro_to_openfermion)
+
+You can run OpenFermion's interactive Jupyter Notebooks, such as the introductory tutorial, in
+[Colab](https://colab.research.google.com/github/quantumlib/OpenFermion/blob/main/examples/intro_to_openfermion.ipynb)
+or
+[MyBinder](https://mybinder.org/v2/gh/quantumlib/OpenFermion/main?filepath=examples%2Fintro_to_openfermion.ipynb).
+
+## Contributing to OpenFermion
+
+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](https://help.github.com/articles/about-pull-requests/) 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](https://www.python.org/dev/peps/pep-0008/) guidelines and use the corresponding
+    [linter](https://pypi.python.org/pypi/pep8) 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](https://quantumai.google/openfermion).
+*   We use [GitHub issues](https://github.com/quantumlib/OpenFermion/issues) for tracking requests
+    and bugs. Please post questions to the [Quantum Computing Stack
+    Exchange](https://quantumcomputing.stackexchange.com/) with an `openfermion` tag.
+
+## Citing OpenFermion<a name="how-to-cite-openfermion"></a><a name="how-to-cite"></a>
+
+OpenFermion is the work of many people. When using OpenFermion for research projects, please cite
+the [published paper](https://doi.org/10.1088/2058-9565/ab8ebc):
+
+> 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](https://zenodo.org/records/15604843).
+
+## Authors
+
+[Ryan Babbush](https://ryanbabbush.com) (Google),
+[Jarrod McClean](https://jarrodmcclean.com) (Google),
+[Nicholas Rubin](https://github.com/ncrubin) (Google),
+[Kevin Sung](https://github.com/kevinsung) (University of Michigan),
+[Ian Kivlichan](https://aspuru.chem.harvard.edu/ian-kivlichan/) (Harvard),
+[Dave Bacon](https://github.com/dabacon) (Google),
+[Xavier Bonet-Monroig](https://github.com/xabomon) (Leiden University),
+[Yudong Cao](https://github.com/yudongcao) (Harvard),
+[Chengyu Dai](https://github.com/jdaaph) (University of Michigan),
+[E. Schuyler Fried](https://github.com/schuylerfried) (Harvard),
+[Craig Gidney](https://github.com/Strilanc) (Google),
+[Brendan Gimby](https://github.com/bgimby) (University of Michigan),
+[Pranav Gokhale](https://github.com/singular-value) (University of Chicago),
+[Thomas Häner](https://github.com/thomashaener) (ETH Zurich),
+[Tarini Hardikar](https://github.com/TariniHardikar) (Dartmouth),
+[Vojtĕch Havlíček](https://github.com/VojtaHavlicek) (Oxford),
+[Oscar Higgott](https://github.com/oscarhiggott) (University College London),
+[Cupjin Huang](https://github.com/pertoX4726) (University of Michigan),
+[Josh Izaac](https://github.com/josh146) (Xanadu),
+[Zhang Jiang](https://ti.arc.nasa.gov/profile/zjiang3) (NASA),
+[William Kirby](https://williammkirby.com) (Tufts University),
+[Xinle Liu](https://github.com/sheilaliuxl) (Google),
+[Sam McArdle](https://github.com/sammcardle30) (Oxford),
+[Matthew Neeley](https://github.com/maffoo) (Google),
+[Thomas O'Brien](https://github.com/obriente) (Leiden University),
+[Bryan O'Gorman](https://ti.arc.nasa.gov/profile/bogorman) (UC Berkeley, NASA),
+[Isil Ozfidan](https://github.com/conta877) (D-Wave Systems),
+[Max Radin](https://github.com/max-radin) (UC Santa Barbara),
+[Jhonathan Romero](https://github.com/jromerofontalvo) (Harvard),
+[Daniel Sank](https://github.com/DanielSank) (Google),
+[Nicolas Sawaya](https://github.com/nicolassawaya) (Harvard),
+[Bruno Senjean](https://github.com/bsenjean) (Leiden University),
+[Kanav Setia](https://github.com/kanavsetia) (Dartmouth),
+[Hannah Sim](https://github.com/hsim13372) (Harvard),
+[Damian Steiger](https://github.com/damiansteiger) (ETH Zurich),
+[Mark Steudtner](https://github.com/msteudtner) (Leiden University),
+[Qiming Sun](https://github.com/sunqm) (Caltech),
+[Wei Sun](https://github.com/Spaceenter) (Google),
+[Daochen Wang](https://github.com/daochenw) (River Lane Research),
+[Chris Winkler](https://github.com/quid256) (University of Chicago),
+[Fang Zhang](https://github.com/fangzh-umich) (University of Michigan),
+and [Emiel Koridon](https://github.com/Emieeel) (Leiden University).
+
+We are happy to include future contributors as authors on later releases.
+
+## Contact
+
+For any questions or concerns not addressed here, please email [email protected].
+
+## Disclaimer
+
+This is not an officially-supported Google product. This project is not eligible for the [Google
+Open Source Software Vulnerability Rewards
+Program](https://bughunters.google.com/open-source-security).
+
+Copyright 2017 The OpenFermion Developers.
+
+<div align="center">
+  <a href="https://quantumai.google">
+    <img width="15%" alt="Google Quantum AI"
+         src="https://raw.githubusercontent.com/quantumlib/OpenFermion/refs/heads/main/docs/images/quantum-ai-vertical.svg">
+  </a>
+</div>