ffsim 0.0.4

Faster simulations of fermionic quantum circuits.

ffsim

Faster simulations of fermionic quantum circuits.

What is ffsim?

ffsim is a software library for simulating fermionic quantum circuits that preserve particle number and the Z component of spin. This category includes many quantum circuits used for quantum chemistry simulations. By exploiting the symmetries and using specialized algorithms, ffsim can simulate these circuits much faster than a generic quantum circuit simulator.

Experimental disclaimer: ffsim is currently an experimental release. Breaking changes may be introduced without warning.

Features

• Fast simulation of fermionic quantum circuits that preserve particle number and the Z component of spin. ffsim supports the simulation of basic fermionic gates and includes specialized routines for simulation of molecular Hamiltonians in the "double-factorized" representation.
• Compatible with PySCF. State vectors use the same indexing convention as PySCF's fci module.

Limitations

• There is no support for operations that do not preserve particle number and the Z component of spin.

Installation

From PyPI

ffsim is available on PyPI. It can be installed by running the command

pip install ffsim

From source

Installing ffsim from source requires a Rust compiler to be present on the system. A Rust compiler can be installed by following the instructions here. Once the Rust compiler is installed, ffsim can be installed by running the command

pip install .

from the root directory of the code repository.

Installing from source has only been tested in a Linux environment.

Known issues

• It may be a bit tricky to get OpenBLAS to link successfully. If you have issues, try the following:
  • Run pip install patchelf.
  • Run pip install -e . twice in a row.

Development

To set up ffsim for development, install it from source in editable mode along with the development requirements:

pip install -e ".[dev]"

If you add or modify any Rust modules, rebuild them by running the command

maturin develop --release

Tests and other code checks are managed using tox. To run the default tox environments, simply run

tox

To run a specific environment, for example, to run the lint checks, do

tox run -e lint

You can also use pytest to run the tests directly. For example,

pytest tests/