QuEST

Introduction

The Quantum Exact Simulation Toolkit is a high performance simulator of universal quantum circuits, state-vectors and density matrices. QuEST is written in C, hybridises OpenMP and MPI, and can run on a GPU. Needing only compilation, QuEST is easy to run both on laptops and supercomputers (in both C and C++), where it can take advantage of multicore, GPU-accelerated and networked machines to quickly simulate circuits on many qubits.

QuEST has a simple interface, independent of its run environment (on CPUs, GPUs or over networks),

hadamard(qubits, 0);

controlledNot(qubits, 0, 1);

rotateY(qubits, 0, .1);

though is flexible

Vector v;
v.x = 1; v.y = .5; v.z = 0;
rotateAroundAxis(qubits, 0, 3.14/2, v);

and powerful

// sqrt(X) with pi/4 global phase
ComplexMatrix2 u = {
    .real = {{.5, .5}, { .5,.5}},
    .imag = {{.5,-.5}, {-.5,.5}}};
unitary(qubits, 0, u);

int controls[] = {1, 2, 3, 4, 5};
multiControlledUnitary(qureg, controls, 5, 0, u);

QuEST can simulate decoherence on mixed states, output QASM, perform measurements, apply general unitaries with any number of control and target qubits, and boasts cheap/fast access to the underlying numerical representation of the state. QuEST offers precision-agnostic real and imaginary (additionally include QuEST_complex.h) number types, the precision of which can be modified at compile-time, as can the target hardware.

Learn more about QuEST at quest.qtechtheory.org, or read the whitepaper. If you find QuEST useful, feel free to cite

Jones, T., Brown, A., Bush, I. et al. 
QuEST and High Performance Simulation of Quantum Computers. 
Sci Rep 9, 10736 (2019) doi:10.1038/s41598-019-47174-9

@article{Jones2019,
  title={{QuEST} and high performance simulation of quantum computers},
  author={Jones, Tyson and Brown, Anna and Bush, Ian and Benjamin, Simon C},
  journal={Scientific reports},
  volume={9},
  number={1},
  pages={1--11},
  year={2019},
  publisher={Nature Publishing Group}
}

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Documentation

Full documentation is available at quest.qtechtheory.org/docs, and the API is available here (all functions listed here). See also the tutorial.

For developers: To regenerate the API doc after making changes to the code, run doxygen doxyconfig/config in the root directory. This will generate documentation in Doxygen_doc/html, the contents of which should be copied into docs/). Make sure that PROJECT_NUMBER in doxyconfig/config is up to date!

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Getting started

QuEST is contained entirely in the files in the QuEST/ folder. To use QuEST, copy this folder to your computer and include QuEST.h in your C or C++ code, and compile using cmake with the provided CMakeLists.txt file. See the tutorial for an introduction. We also include example submission scripts for using QuEST with SLURM and PBS.

Quick Start

MacOS & Linux

MacOS and Linux users can clone this repository to your machine through the terminal:

git clone https://github.com/quest-kit/QuEST.git
cd QuEST

Compile the example using

mkdir build
cd build
cmake ..
make

then run it with

./demo

Windows

Windows users should install Build Tools for Visual Studio, CMake and MinGW-w64. Then, in a Developer Command Prompt for VS, run

git clone "https://github.com/quest-kit/QuEST.git"
cd QuEST

mkdir build
cd build
cmake .. -G "MinGW Makefiles"
make

demo.exe

Tests

Additionally, you can run QuEST's rigorous unit tests in your own environment, which should take no longer than ten minutes.

mkdir build
cd build
cmake .. -DTESTING=ON
make 
make test

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Contact

To file a bug report or feature request, raise a github issue. For additional support, email quest@materials.ox.ac.uk. You can view the list of contributors to QuEST in AUTHORS.txt.

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Acknowledgements

We sincerely thank the following external contributors to QuEST.

• HQS Quantum simulations for contributing mixDamping on CPU.
• Kshitij Chhabra for patching some validation bugs.
• Drew Silcock for patching the multithreaded build on MacOS.
• Zach van Rijn for patching the multithreading code for GCC-9 OpenMP-5 compatibility
• @SachinCompton for patching the GPU CMake Release build

QuEST uses the mt19937ar 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 by Randy Meyers and Dr. Thomas Plum

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Licence

QuEST is released under a MIT Licence

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Related projects -- QuEST utilities and extensions

• QuESTlink: a Mathematica package allowing symbolic circuit manipulation and high performance simulation with remote accelerated hardware.
• 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.