qsim and qsimh

The libraries qsim and qsimh are high-performance quantum circuit simulators written in C++ and offering a Python API wrapper. qsim is a Schrödinger full state-vector simulator, and qsimh is a hybrid Schrödinger-Feynman simulator. They use gate fusion, AVX/FMA vectorized instructions, and multi-threading using OpenMP to achieve state of the art simulations of quantum circuits. Both can be easily used from Cirq, a framework for writing, manipulating, and running Noisy Intermediate-Scale Quantum (NISQ) circuits.

qsim and qsimh together are available as the Python package qsimcirq. The project whose page on PyPI you are reading now (i.e., qsim) only acts to reference qsimcirq and point people to the that project.