PauliEngine: Fast Arithmetics for Quantum Operators

See more in arXiv:2601.02233

This project is currently in beta. Some features are incomplete or still under development.
The following items are planned or not yet fully implemented:

• A detailed online Documentation of PauliEngines functionality.

• Installation via pip.

• A comprehensive test suite.

Examples

Operator Construction

import pauliengine as pe
# Example : Z on qubit 0 with coefficient 1.0
p1 = pe.PauliString ((1.0, {0: "Z"}))

# Example : X on qubit 1 with coefficient "a" ( symbolic )
p2 = pe.PauliString (("a", {1: "X"}))

# Example : OpenFermion style
p3 = pe.PauliString ((1.0, [("X", 0), ("Y", 2) ]))

Standard Operations

# Addition:
p4 = p2 + p3
# Multiplication
p5 = p4 * p1
# fast commutators
c = p1.commutator(p2)

Parametrized Operators

# create PauliString objects
p1 = pe.PauliString ((1.0 , {0: "Z"})) # not parametrized
p2 = pe.PauliString (("a", {1: "X"}))  # parametrized
# assemble operator
H = QubitHamiltonian([p1 , p2 ])

In beta version, mixed types need to be created like this (create atomic PauliStrings, then assemble operator)

Operations on Parametrized Operators

# Differentiate
dH = H.diff ("a")
# Substitute
H2 = H.subs ({"a": 2.0})

Installation and Build Guide

This guide explains how to install and build SymEngine and integrate it into a C++ project on Windows using Conan, CMake, and Visual Studio.

Note: When the project is built without SymEngine, runtime performance drops significantly!

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Prerequisites

Before you begin, make sure you have the following installed:

• Git (installed and accessible from the command line)

• CMake (installed and added to your PATH)

• Python (for installing Conan)

Step 1: Install Conan

Install Conan via pip:

pip  install  conan

conan  profile  detect

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Step 2: Install SymEngine

MacOS only

conan install --build=symengine/0.14.0

Step 3 Clone Project

Clone the project into desired directory. If nanobind is missing, clone nanobind with the option --recursive into src.

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Step 4: Integrate SymEngine in Your Project

In the directory src

conan  install  .  --output-folder=build  --build=missing

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Step 5: Configure with CMake

cd  build

cmake  ..  -DCMAKE_TOOLCHAIN_FILE=conan_toolchain.cmake

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Step 6: Build the Project

cmake  --build  .  --config  Release

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Step 7: Using the module

When building this project as a Python extension module using nanobind, the resulting file type depends on the operating system:

• Linux: .so

• macOS: .so

• Windows: .pyd

Although Linux and macOS both generate .so files, they use different binary formats (ELF on Linux, Mach-O on macOS). On Windows, Python loads native modules using the .pyd extension, which is similar to a DLL.

The final compiled extension module will be located in:

src/build/Release

This file can now be used in any Python project, and its functionality can be accessed via:

 import PauliEngine