quantlop 0.0.2

High-performance quantum simulator for matrix-free Hamiltonian evolution

quantlop

High-performance quantum simulator for matrix-free Hamiltonian evolution

Introduction

quantlop is a high-performance simulator for the time evolution of quantum systems whose Hamiltonians can be written as sparse sums of Pauli words. It integrates with PennyLane, so Hamiltonians can be defined with familiar Python operators while the compute-intensive work runs in C++.

Rather than constructing the full Hamiltonian matrix, quantlop applies each Pauli word as a linear operator directly to the state vector. It then uses a Krylov method to numerically approximate the action of the matrix exponential. This matrix-free approach dramatically reduces memory usage and avoids costly dense-matrix operations, making larger simulations more practical.

Installation

The project requires Python 3.11 or later and a C++20-compatible compiler.

pip install quantlop

On macOS, install the OpenMP runtime before installing quantlop:

brew install libomp
pip install quantlop

Usage example

import numpy as np
import pennylane as qp
import quantlop

# set number of qubits
nq = 3

# define Hamiltonian in Pauli basis
op = 0.5 * qp.Z(0) @ qp.Z(1) + 0.2 * qp.Y(0) @ qp.X(2)
ham = quantlop.Hamiltonian.from_pennylane(op, nq)

# prepare initial state vector
psi = np.zeros(2**nq, dtype=complex)
psi[0] = 1.0

# evolve state vector
evolved_psi = quantlop.evolve(ham, psi)

Multi-threading

Evolution is serial by default. Set num_threads to a positive integer to use that many OpenMP threads, or to "auto" to use the CPU count reported by the operating system:

evolved_psi = quantlop.evolve(ham, psi, num_threads="auto")

Development

The Python package is built with scikit-build-core, while the numerical C++ code is kept in the standalone quantlop_core CMake target.

Run the Python test suite with:

python -m pip install -e .[dev]
python -m pytest -v

Run the native C++ test suite with:

cmake -S . -B build
cmake --build build
ctest --test-dir build --output-on-failure

Install the pre-commit hook to format Python and C++ files automatically:

pre-commit install