# Intel Quantum Simulator¶

Intel Quantum Simulator (Intel-QS), also known as qHiPSTER (The Quantum High Performance Software Testing Environment), is a simulator of quantum circuits optimized to take maximum advantage of multi-core and multi-nodes architectures. It is based on a complete representation of the qubit state, but avoids the explicit representation of gates and other quantum operations in terms of matrices. Intel-QS uses MPI (message-passing-interface) protocols to handle the communication between distributed resources that are used to store and manipulate the quantum state.

## Build instructions¶

Intel-QS builds as a shared library which, once linked to the application program, allows to take advantage of the high-performance implementation of circuit simulations. The library can be built on a variety of different systems, from laptop to HPC server systems.

The directory structure of the repository can be found in intel-qs/docs/directory_structure.md.

The library object is: /builb/lib/libiqs.so

### Requirements¶

The following packages are required by the installation:

• CMake tools version 3.12+

• MPICH3 library for enabling the distributed communication

• optional: MKL for distributed random number generation

• optional: PyBind11 (installed via conda, not pip) required by the Python bunding of Intel-QS

The first step is cloning the repository:

  git clone https://github.com/iqusoft/intel-qs.git
cd intel-qs


### Use Intel Parallel Studio compilers to build Intel-QS¶

If you wish to build Intel-QS using the latest Intel compiler technologies, then you need to configure your environment properly according to that tool’s documentation. Assuming that you have installed Intel Parallel Studio in the standard location on your system, you should invoke the following scripts through the source command on Linux.

  source /opt/intel/bin/compilervars.sh -arch intel64 -platform linux
source /opt/intel/compiler_and_libraries/linux/mpi/intel64/bin/mpivars.sh


Now, use CMake to generate the appropriate makefiles to use the Intel Parallel Studio compilers. The installation follows the out-of-source building and requires the creation of the directory build. This directory is used to collect all the files generated during the installation process.

  mkdir build
cd build
CXX=mpiicpc cmake -DIqsMPI=ON -DIqsUtest=ON ..
make


By default, MKL is required when Intel compilers are used.

To re-build Intel-QS with different settings or options, we recommend to delete all content of the build directory and then restart from the CMake command.

### Use standard GNU tools to build Intel-QS¶

If you wish to build Intel-QS using only standard GNU compilers type:

  mkdir build
cd build
CXX=g++ cmake -DIqsMPI=OFF ..
make


By default, MKL is not required when GNU compilers are used. Optionally, MPI can be included by setting the option -DIqsMPI=ON instead. You must ensure that you have at least version 3.1 of MPICH installed for the build to succeed. https://www.mpich.org

### Enable MPI protocol for distributed memory use¶

The above installation enables MPI functionalities to deploy Intel-QS on High Performance Computing and Cloud Computing infrastructures. There is the option of disabling MPI: simply set the CMake option selection to -DIqsMPI=OFF (or just omit the option selection since MPI is disabled by default in the CMake build).

### Enable Latest Vector Capability¶

To compile with the latest instruction set supported by your architecture, there is the option -DIqsNative. Compiled with -DIqsNative=ON, the latest vector instructions available on your machine, e.g. AVX2, AVX512, are used. By default, -DIqsNative=OFF.

If the machine you compile and the machine you run have different vector capabilities, turning on IqsNative=ON might cause run-time problems.

Underneath, this option uses -xhost with Intel compilers and -march=native with GNU compilers.

### Enable Python binding (only available without MPI)¶

By default, whenever MPI is disabled, the building process includes the Python binding for Intel-QS. The binding code uses the Pybind11 library which needs to be installed via ‘conda’ (and not simply with pip) to include the relevant information in CMake. See this page for more info on this issue.

To disable the Python wrap, even without MPI, set the CMake option selection to -DIqsPython=OFF.

### Unit test¶

By default, with MPI either enabled or disabled, the building process includes a suite of unit tests written in the googletest framework. Following the recommended integration, the CMake building process automatically downloads the up-to-date repository of gtest and installs it in the build path.

To disable the unit tests, set the CMake option selection to -DIqsUtest=OFF.

To run the unit tests, from /build launch the executable ./bin/utest.

## Docker: build image and run/execute container¶

Dockerfile includes the instructions to build the docker image of an Ubuntu machine with Intel-QS already installed. The image can be ‘run’ to create a container. The container can be ‘executed’ to login into the machine.

  docker build -t qhipster .
docker run -d -t qhipster
docker ps
docker exec -itd <container_id> /bin/bash


If Docker is used on a Windows host machine, the last line should be substituted by: winpty docker exec -itd <container_id> //bin/bash.

## Getting started with Intel-QS¶

The simplest way of familiarize with the Intel Quantum Simulator is by exploring the tutorials provided in the directory tutorials/. In particular, the code tutorials/get_started_with_IQS.cpp provides step-by-step description of the main commands to: define a qubit register object, perform quantum gates, measure one or multiple qubits.

If the Python bindings were enabled, the same learning can be performed using the iPython notebook tutorials/get_started_with_IQS.ipynb.

## How to contribute¶

Thanks for your interest in the project! We welcome pull requests from developers of all skill levels. If you would like to contribute to Intel-QS, please take a look to our contributing policy and also to the code of conduct. For any bug, we use GitHub issues GitHub issues. Please submit your request there.