[](https://arxiv.org/abs/2110.05899) [](https://quantum-journal.org/papers/q-2022-07-20-768/)

Description

TFermion is a library that allows to calculate the expected cost T-gate cost of performing Quantum Phase Estimation with different methods for arbitrary molecules and Hamiltonians. It uses methods from OpenFermion and Pyscf and interfaces with PubChem to download the corresponding molecular data.

You can read our paper at TFermion: A non-Clifford gate cost assessment library of quantum phase estimation algorithms for quantum chemistry.

The current implemented methods (we list the arxiv papers) are:

• qdrift, the qDRIFT method from https://arxiv.org/abs/1811.08017.
• rand_ham, the Random Hamiltonian simulation method from https://arxiv.org/abs/1811.08017.
• taylor_naive, the Naïve Taylorization method from from https://arxiv.org/abs/1506.01020.
• taylor_on_the_fly, the Taylor on-the-fly method from https://arxiv.org/abs/1506.01020.
• configuration_interaction, the method from https://arxiv.org/abs/1506.01029.
• low_depth_trotter, the Trotterization method in plane waves from https://arxiv.org/abs/1706.00023.
• low_depth_taylor, the Naïve Taylorization method in plane waves from https://arxiv.org/abs/1706.00023.
• low_depth_taylor_on_the_fly, the on-the-fly Taylorization method in plane waves from https://arxiv.org/abs/1706.00023.
• shc_trotter, similar to low_depth_trotter but using the SHC bound from https://arxiv.org/abs/2107.07238, developing over the work of https://arxiv.org/abs/2012.09194.
• linear_t, the method from https://arxiv.org/abs/1805.03662.
• sparsity_low_rank, the method from https://arxiv.org/abs/1902.02134.
• interaction_picture, the method from https://arxiv.org/abs/1805.00675.

Other methods not yet implemented include:

• The double rank factorization from https://arxiv.org/abs/2007.14460.
• The tensor hypercontraction method from https://arxiv.org/abs/2011.03494.
• The qubitization and interaction picture methods from https://arxiv.org/abs/1807.09802 and https://arxiv.org/abs/2105.12767.
• Other Trotter methods with different bounds such as those from https://arxiv.org/abs/2107.07238.

How to install

First, install dependencies

# clone project   
git clone https://github.com/PabloAMC/TFermion

# install chemistry libraries
pip install openfermion pyscf

# install wrappers for chemistry libraries
pip install openfermionpsi4 openfermionpyscf

# install auxiliary libraries
pip install pandas numpy h5py scipy sympy matplotlib

How to run

python main.py [molecule name] [method name]

Examples

You can find some snippet examples in the folder snippets

Contributing

We would love TFermion to become an useful tool for reseachers. If you want to join this mission, drop us a line at pabloamo@ucm.es. Things that can be done include implementing new methods (see the snippet in the snippet folder), or counting qubits. Also, some adaptation for periodic systems might be useful.

Authorship

Citation

@article{casares2022tfermion,
  doi = {10.22331/q-2022-07-20-768},
  url = {https://doi.org/10.22331/q-2022-07-20-768},
  title = {{TF}ermion: {A} non-{C}lifford gate cost assessment library of quantum phase estimation algorithms for quantum chemistry},
  author = {Casares, Pablo A. M. and Campos, Roberto and Martin-Delgado, M. A.},
  journal = {{Quantum}},
  issn = {2521-327X},
  publisher = {{Verein zur F{\"{o}}rderung des Open Access Publizierens in den Quantenwissenschaften}},
  volume = {6},
  pages = {768},
  month = jul,
  year = {2022}
}

Contributors

Pablo A. M. Casares (Universidad Complutense de Madrid) and Roberto Campos (Universidad Complutense de Madrid).

License

Apache 2.0 license.