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;
u.r0c0 = (Complex) {.real=.5, .imag= .5};
u.r0c1 = (Complex) {.real=.5, .imag=-.5}; 
u.r1c0 = (Complex) {.real=.5, .imag=-.5};
u.r1c1 = (Complex) {.real=.5, .imag= .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 gates with any number of control qubits, and provides cheap/fast access to the underlying statevector. 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.

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](CMakeLists.txt file). See the tutorial for an introduction, and view the full API here.

We also include example submission scripts for using QuEST with SLURM and PBS.

Quick Start

Copy or clone this repository to your machine. E.g. in the desired directory, enter

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

at terminal. You can then compile the example using

mkdir build
cd build
cmake ..
make

then run it with

./demo

and afterward, clean up with

make clean

or, to remove the build directory entirely, from the root directory

rm -r build

The program will print information about your execution environment and some simple operations on a three qubit system. See the tutorial for a better introduction.

Additionally, you can run unit tests to see if QuEST runs correctly in your environment, using

make test

This requires Python 3.4+.

Documentation

View the API here, and check compatible compiler versions here.

For developers: To recreate the full documentation after making changes to the code, run doxygen doxyconf in the root directory. This will generate documentation in Doxygen_doc/html, and can be accessed through index.html in that folder.

Acknowledgements

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

Thanks to HQS Quantum simulations for contributing the applyOneQubitDampingError function.

Licence

QuEST is released under a MIT Licence

Related projects -- QuEST utilities and extensions

• 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.