Installation instructions

Quantum++ is a header-only library that uses CMake as its build/install system. Quantum++ is platform-independent, supporting UNIX (including macOS) and UNIX-like operating systems (e.g., Linux), as well as Windows.

Pre-requisites

C++17 compliant compiler, e.g., GCC , Clang , MSVC etc.
CMake
Eigen 3 linear algebra library. If missing, it will be installed automatically by CMake as a build dependency.

Optional

Python 3 for building and running the pyqpp Python 3 wrapper
MATLAB compiler shared libraries and include header files, in case you want to enable interoperability with MATLAB. If enabled, allows applications built with Quantum++ to save/load Quantum++ matrices and vectors to/from MATLAB.

Configuring the system

First configure the system via CMake to use an out-of-source build directory (e.g., ./build) by executing (in a terminal/console/command prompt) under the project's root directory

cmake -B build

Building the examples and/or unit tests

To build the examples, execute

cmake --build build --target examples --parallel 8

The above command builds all examples as executables in ./build. The --parallel 8 flag instructs CMake to build in parallel using 8 threads, modify accordingly.

To build the unit tests, execute

cmake --build build/unit_tests --target unit_tests --parallel 8

Tu run the unit tests, execute

ctest --test-dir build

To build only a specific target, execute, e.g.,

cmake --build build --target bb84

The command above builds only the example examples/bb84.cpp and outputs the executable ./build/bb84[.exe].

CMake optional arguments and flags

Note that all CMake flags below that start with QPP_ and QASMTOOLS_ propagate to subprojects that use Quantum++ in their corresponding CMakeLists.txt via findpackage(qpp ...).

Optional argument	Value	Description
`CMAKE_INSTALL_PREFIX`	`/path/to/install`	Installs Quantum++ header files in a non-standard location (e.g., due to lack of admin. rights)

`QPP_MATLAB`	`ON/OFF` [`OFF` by default]	Enables (if available)/disables interoperability with MATLAB, allowing to detect MATLAB installation automatically. If enabled, allows applications to save/load Quantum++ matrices and vectors to/from MATLAB.
`QPP_OPENMP`	`ON/OFF` [`ON` by default]	Enables (if available)/disables OpenMP multi-processing library
`QASMTOOLS_QASM2_SPECS`	`ON/OFF` [`OFF` by default]	Enables/disables using the OpenQASM 2.0 standard instead of Qiskit specifications; see `DISCREPANCIES.md`

`QPP_BIGINT`	`default`, etc. [`default` by default]	Signed big integer type (`qpp::bigint`)
`QPP_FP`	`default`, etc. [`default` by default]	Floating-point type (`qpp::realT`)
`QPP_IDX`	`default`, etc. [`default` by default]	Integer index type (`qpp::idx`)

`SANITIZE`	`ON/OFF` [`OFF` by default]	Enable code sanitizing (only for GCC/Clang)

Installing Quantum++

UNIX/UNIX-like/Windows

To install Quantum++ (after Configuring the system), execute in a terminal/console (UNIX/UNIX-like systems)

sudo cmake --build build --target install

or in an Administrator Command Prompt (Windows)

cmake --build build --target install

The above commands install Quantum++ in /usr/local/include/qpp on UNIX/UNIX-like platforms, and in C:\Program Files (x86)\qpp on Windows platforms.

To uninstall, execute in a terminal/console (UNIX/UNIX-like systems)

sudo cmake --build build --target uninstall

or in an Administrator Command Prompt (Windows)

cmake --build build --target uninstall

FreeBSD

We are proud to be part of the FreeBSD operating system as an official package. If you are running FreeBSD, you can install Quantum++ with

sudo pkg install quantum++

and uninstall it with

sudo pkg remove quantum++

macOS/Linux

If you are running macOS or Linux, you can install Quantum++ via Homebrew with

brew install quantum++

and uninstall it with

brew uninstall quantum++

Building and running a standalone application that uses Quantum++

Below is a minimal CMakeLists.txt of a standalone application that uses Quantum++. For simplicity, we assume that the whole application is located in a single file src/main.cpp, and the CMakeLists.txt is located in the project's root directory.

cmake_minimum_required(VERSION 3.15)
project(standalone)
set(CMAKE_CXX_STANDARD 17)

# If the Quantum++ installation path was non-standard, i.e., specified by
#
# cmake -B build -DCMAKE_INSTALL_PREFIX=/path/to/installed/qpp
#
# then uncomment the following line and replace the installation path with yours

# set(CMAKE_PREFIX_PATH "/path/to/installed/qpp")

find_package(qpp REQUIRED)
add_executable(standalone src/main.cpp)
target_link_libraries(standalone PUBLIC ${QPP_LINK_DEPS} libqpp)

Do not forget to ALWAYS add ${QPP_LINK_DEPS} (verbatim) to target_link_libraries()! (last line of the CMakeLists.txt file above).

Configure the application in an out-of-source directory by executing

cmake -B build

followed by building the application with

cmake --build build

The commands above builds the standalone executable inside the build directory.

Building and running a standalone application that uses Quantum++ without a build system

Quantum++ is a header-only library. Hence, you can technically build an application that uses Quantum++ without using a building system, by simply using the compiler and specifying the location to all required dependencies, like below (assumes UNIX/UNIX-like, adapt accordingly for Windows)

g++ -pedantic -std=c++17 -Wall -Wextra -Weffc++ -fopenmp \
    -O3 -DNDEBUG -DEIGEN_NO_DEBUG
    -isystem $HOME/eigen3 -I $HOME/qpp/include -I $HOME/qpp/qasmtools/include \
     src/main.cpp -o my_qpp_app

If you intend to go via this route, we assume that you are familiar with how compilers work, so we won't add any more explanations to what the line above does.

Additional platform-specific instructions

macOS/OS X specific instructions

We highly recommend installing clang via Homebrew, since the native AppleClang does not offer OpenMP support.
In case you get any compiler or linker errors when OpenMP is enabled, you need to install the libomp package, e.g., execute

brew install libomp

MATLAB support under Windows

If building under Windows with MATLAB support, please add the location of libmx.dll and libmat.dll (the .dll and not the .lib files) to your PATH environment variable. For example, on our platform they are located under C:\Program Files\MATLAB\R2021a\bin\win64.

Python 3 wrapper

pyqpp is a Python 3 wrapper for Quantum++. pyqpp requires the same dependencies as Quantum++, and can be installed using pip

pip install git+https://github.com/softwareQinc/qpp

For more details, please see pyqpp/README.md.

Platform-dependent issues

SunOS/OpenIndiana

The Python3 wrapper pyqpp doesn't compile under SunOS/OpenIndiana due to errors in <cmath> such as

no member named 'llround' in the global namespace; did you mean 'lround'?

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