[](https://quest.qtechtheory.org) [](https://GitHub.com/QuEST-Kit/QuEST/releases/) [](https://quest-kit.github.io/QuEST/modules.html) [](https://github.com/QuEST-Kit/QuEST/actions) [](LICENCE.txt) The **Quantum Exact Simulation Toolkit** is a high performance simulator of quantum circuits, state-vectors and density matrices. QuEST uses **multithreading**, **GPU acceleration** and **distribution** to run lightning first on laptops, desktops and networked supercomputers. QuEST *just works*; it is stand-alone, requires no installation, and is trivial to compile and run. QuEST hybridises [OpenMP](https://www.openmp.org/) and [MPI](https://www.mpi-forum.org/) with _huge_ compiler support to run on all sorts of multicore, multi-CPU and distributed hardware, uses [HIP](https://docs.amd.com/bundle/HIP-Programming-Guide-v5.3) to run on AMD GPUs, integrates [cuQuantum](https://developer.nvidia.com/cuquantum-sdk) and [Thrust](https://developer.nvidia.com/thrust) for cutting-edge performance on modern NVIDIA GPUs, and has a custom kernel backend to run on older CUDA-compatible GPUs. And it hides these deployment modes behind a single, seamless interface. [](http://www.open-std.org/jtc1/sc22/wg14/www/standards.html#9899) [](https://isocpp.org/wiki/faq/cpp11)    [](https://www.openmp.org/) [](https://www.mpi-forum.org/) [](https://developer.nvidia.com/cuda-zone) [](https://docs.amd.com/bundle/HIP-Programming-Guide-v5.3) [](https://developer.nvidia.com/cuquantum-sdk) QuEST is developed by the [QTechTheory](http://qtechtheory.org/) group at the University of Oxford, and [these authors](https://github.com/QuEST-Kit/QuEST/blob/master/AUTHORS.txt). To learn more: - see the [tutorial](https://github.com/QuEST-Kit/QuEST/blob/master/examples/README.md) - view the [documentation](https://quest-kit.github.io/QuEST/modules.html) - visit the [website](https://quest.qtechtheory.org/) - see some [examples](https://github.com/QuEST-Kit/QuEST/blob/master/examples/) - read the [whitepaper](https://www.nature.com/articles/s41598-019-47174-9), which featured in Scientific Report's [Top 100 in Physics](https://www.nature.com/collections/ecehgdfcba/) :trophy: [](https://doi.org/10.1038/s41598-019-47174-9) [](mailto:quest@materials.ox.ac.uk) --------------------------------- ## :tada:  Introduction QuEST has a simple interface, which is agnostic to its runtime environment, between CPUs, GPUs and over networks. ```C hadamard(qubits, 0); controlledRotateX(qubits, 0, 1, angle); double prob = calcProbOfOutcome(qubits, 0, outcome); ``` Yet, it is flexible ```C Vector v; v.x = 1; v.y = .5; v.z = 0; rotateAroundAxis(qubits, 0, angle, v); ComplexMatrix2 u = { .real = {{.5, .5}, { .5,.5}}, .imag = {{.5,-.5}, {-.5,.5}}}; unitary(qubits, 0, u); mixDepolarising(qubits, 0, prob); ``` and extremely powerful ```C ComplexMatrixN u = createComplexMatrixN(5); int ctrls[] = {0, 1, 2}; int targs[] = {5, 20, 15, 10, 25}; multiControlledMultiQubitUnitary(qubits, ctrls, 3, targs, 5, u); ComplexMatrixN k1, k2, k3 = ... mixMultiQubitKrausMap(qubits, targs, 5, {k1, k2, k3}, 3); double val = calcExpecPauliHamil(qubits, hamiltonian, workspace); applyTrotterCircuit(qubits, hamiltonian, time, order, repetitions); ``` --------------------------------- ## :white_check_mark:  Features QuEST supports: - :ballot_box_with_check:   **density matrices** for precise simulation of noisy quantum computers - :ballot_box_with_check:   **general unitaries** with any number of control and target qubits - :ballot_box_with_check:   **general decoherence channels** of any dimension - :ballot_box_with_check:   **general Hermitian operators** in the Pauli basis - :ballot_box_with_check:   **many *many* operators**, including even [Pauli gadgets](https://quest-kit.github.io/QuEST-develop-doc/group__unitary.html#ga34aa4865c92f9aa5d898c91286c9eca5), [analytic phase functions](https://quest-kit.github.io/QuEST-develop-doc/group__operator.html#ga467f517abd18dbc3d6fced84c6589161) and [Trotter circuits](https://quest-kit.github.io/QuEST-develop-doc/group__operator.html#ga35b6321c578a8c69470132b5ee95f930) - :ballot_box_with_check:   **many tools to analyse** quantum states, such as calculations of [probability](https://quest-kit.github.io/QuEST-develop-doc/group__calc.html#gad0cc08d52cad5062553d6f78126780cc), [fidelity](https://quest-kit.github.io/QuEST-develop-doc/group__calc.html#gaa266ed6c8ae5d0d0f49e1ac50819cffc), and [expected value](https://quest-kit.github.io/QuEST-develop-doc/group__calc.html#ga82f17e96a4cb7612fb9c6ef856df3810) - :ballot_box_with_check:   **variable precision** through a `qreal` numerical type which can use single, double or quad precision - :ballot_box_with_check:   **QASM output** to verify simulated circuits - :ballot_box_with_check:   **direct access to amplitudes** for rapid custom modification of the quantum state - :ballot_box_with_check:   **native compilation** on MacOS, Linux and Windows, through Clang, GNU, Intel, and MSVC compilers --------------------------------- ## :book:  Documentation - The [tutorial](/examples/README.md) includes instructions for - [compiling](/examples/README.md#compiling) QuEST - [running](/examples/README.md#running) QuEST locally and on supercomputers - [testing](/examples/README.md#testing) QuEST using the comprehensive [unit tests](https://quest-kit.github.io/QuEST/group__unittest.html)

- The [documentation](https://quest-kit.github.io/QuEST/modules.html) is divided into the following modules (collated [here](https://quest-kit.github.io/QuEST/QuEST_8h.html)) - [data structures](https://quest-kit.github.io/QuEST/group__type.html) - [initialisations](https://quest-kit.github.io/QuEST/group__init.html) - [unitaries](https://quest-kit.github.io/QuEST/group__unitary.html) - [gates](https://quest-kit.github.io/QuEST/group__normgate.html) - [decoherence](https://quest-kit.github.io/QuEST/group__decoherence.html) - [operators](https://quest-kit.github.io/QuEST/group__operator.html) - [calculations](https://quest-kit.github.io/QuEST/group__calc.html) - [QASM](https://quest-kit.github.io/QuEST/group__qasm.html)

- Additional utilities for debugging and testing are documented below - [debugging](https://quest-kit.github.io/QuEST/group__debug.html) - [unit tests](https://quest-kit.github.io/QuEST/group__unittest.html) - [testing utilities](https://quest-kit.github.io/QuEST/group__testutilities.html) > **For developers**: QuEST's doc is automatically regenerated when the `master` branch is updated via [Github Actions](https://github.com/features/actions). To locally regenerate the doc, run `doxygen doxyconfig/config` in the root directory, which generates html documentation in `Doxygen_doc/html`. --------------------------------- ## :rocket:  Getting started To rocket right in, download QuEST with [git](https://git-scm.com/) at the terminal ```bash git clone https://github.com/quest-kit/QuEST.git cd QuEST ``` Compile the [tutorial](/examples/README.md) example ([source](/examples/tutorial_example.c)) using [cmake](https://cmake.org/) and [make](https://www.gnu.org/software/make/) ```bash mkdir build cd build cmake .. make ``` then run it with ```bash ./demo ```
> **Windows** users should install [Build Tools](https://visualstudio.microsoft.com/downloads/#build-tools-for-visual-studio-2019) for Visual Studio, and [CMake](https://cmake.org/download/), and run the above commmands in the *Developer Command Prompt for VS*, though using build commands > ```bash > cmake .. -G "NMake Makefiles" > nmake > ``` > If using MSVC and NMake in this way fails, users can forego GPU acceleration, download > [MinGW-w64](https://sourceforge.net/projects/mingw-w64/), and compile via > ```bash > cmake .. -G "MinGW Makefiles" > make > ``` --------------------------------- ## :heart:  Acknowledgements We sincerely thank the following external contributors to QuEST. - [Jakub Adamski](https://github.com/jjacobx) for optimising distributed communication of max-size messages. - [Bruno Villasenor Alvarez](https://github.com/bvillasen) of [AMD](https://www.amd.com/en.html) for porting the GPU backend to [HIP](https://github.com/ROCm-Developer-Tools/HIP), for compatibility with AMD GPUs. - [HQS Quantum simulations](https://quantumsimulations.de/) for contributing `mixDamping` on CPU. - [Kshitij Chhabra](https://github.com/kshitijc) for patching some validation bugs. - [Drew Silcock](https://github.com/drewsilcock) for patching the multithreaded build on MacOS. - [Zach van Rijn](https://github.com/zv-io) for patching the multithreading code for GCC-9 OpenMP-5 compatibility. - [SchineCompton](https://github.com/SchineCompton) for patching the GPU CMake release build. - [Christopher J. Anders](https://github.com/chr5tphr) for patching the multithreading (when default off) and GPU builds (revising min cmake). - [Gleb Struchalin](https://github.com/glebx-f) for patching the cmake standalone build. - [Milos Prokop](https://github.com/Milos9304) for serial prototyping of `initDiagonalOpFromPauliHamil`. QuEST uses the [mt19937ar](http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/emt19937ar.html) Mersenne Twister algorithm for random number generation, under the BSD licence. QuEST optionally (by additionally importing `QuEST_complex.h`) integrates the [language agnostic complex type](http://collaboration.cmc.ec.gc.ca/science/rpn/biblio/ddj/Website/articles/CUJ/2003/0303/cuj0303meyers/index.htm) by Randy Meyers and Dr. Thomas Plum --------------------------------- ## :newspaper:  Related projects - [QuESTlink](https://questlink.qtechtheory.org)
a Mathematica package enabling symbolic circuit manipulation, analytic simulation, visualisation and high performance simulation with remote accelerated hardware. - [pyQuEST](https://github.com/rrmeister/pyQuEST/tree/master)
a python interface to QuEST, based on Cython, developed within the [QTechTheory](https://qtechtheory.org) group. Please note, pyQuEST is currently in the alpha stage. - [PyQuEST-cffi](https://github.com/HQSquantumsimulations/PyQuEST-cffi)
a python interface to QuEST based on cffi developed by HQS Quantum Simulations. Please note, PyQuEST-cffi is currently in the alpha stage and not an official QuEST project.