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.

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 the provided makefile. 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.

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

cp examples/tutorial_example.c .
make

then run it with

./demo

and afterward, clean up with

make clean
rm tutorial_example.c

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, run cd tests then ./runTests.sh to test QuEST runs correctly in your environment, as specified in makefile.

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.

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

QuEST is released under a MIT Licence