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Version 3.1 - 11 January 2022

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Build status - CircleCI Linux/macOS Build status


Quantum++ is a modern C++ general purpose quantum computing library, composed solely of template header files. Quantum++ is written in standard C++17 and has very low external dependencies, using only the Eigen 3 linear algebra header-only template library and, if available, the OpenMP multi-processing library.

Quantum++ is not restricted to qubit systems or specific quantum information processing tasks, being capable of simulating arbitrary quantum processes. The main design factors taken in consideration were the ease of use, high portability, and high performance. The library's simulation capabilities are only restricted by the amount of available physical memory. On a typical machine (Intel i5 8Gb RAM) Quantum++ can successfully simulate the evolution of 25 qubits in a pure state or of 12 qubits in a mixed state reasonably fast.

To report any bugs or ask for additional features/enhancements, please submit an issue with an appropriate label.

If you are interested in contributing to this project, feel free to contact us. Alternatively, fork the repository, create a custom branch, add your contribution, then finally create a pull request. If we accept the pull request, we will merge your custom branch with the latest main/development branch. The latter will eventually be merged into a future release version. To contribute, it is preferable to have a solid knowledge of modern C++ (preferably C++17 or later), including templates and the standard library, a basic knowledge of quantum computing and linear algebra, and working experience with Eigen 3.

For additional Eigen 3 documentation see For a simple Eigen 3 quick ASCII reference see

Copyright (c) 2013 - 2022 softwareQ Inc. All rights reserved.


Quantum++ is distributed under the MIT license. Please see the LICENSE file for more details.

Installation instructions and further documentation

Please see the installation guide and the comprehensive Wiki for further documentation and detailed examples.

To generate the full official API documentation in both LaTeX and HTML formats run doxygen on the Doxyfile file. The tool dot from the Graphviz package must be installed (sudo apt-get install graphviz on Ubuntu/Debian Linux, or brew install graphviz on macOS). Running doxygen will generate the documentation directory doc containing both the HTML and LaTeX documentation.

The HTML documentation file will be accessible by opening doc/html/index.html with the browser of your choice. To generate a PDF file of the documentation, run

latexmk -pdf refman.tex

from the doc/latex directory or compile the file doc/latex/refman.tex with your LaTeX compiler. This will create the doc/latex/refman.pdf documentation file. Consult your favourite LaTeX manual for how to compile/build LaTeX files under your specific operating system.

Python 3 wrapper

pyqpp is a Python 3 wrapper for Quantum++. pyqpp requires the same dependencies as Quantum++, and can be installed using pip:

pip install git+

Important: If the installation fails due to your system being unable to detect the location of the Eigen3 matrix library, set the environment variable EIGEN3_INSTALL_DIR to point to the location of the Eigen3 library (include the include/eigen3 part of the path).

For more details, please see pyqpp/ .