This examples describes how to set up molecular data and perform the experiment in arXiv:2004.04174. The goal in providing this code is transparency and reproducibility. This is a living code base and various pieces may be integrated into OpenFermion over time.
The HFVQE experiment seeks to error mitigate the basis rotation circuit primitive. This is achieved by post-selection, variational relaxation of the parameters, and purification. The tutorial demonstrates how to collect data and perform analysis such as extracting fidelity and performing optimization.
Quickstart
The quickstart tutorial provided with this module describes how to initialize and run a Hartree-Fock VQE calculation. It steps through estimating the 1-RDM given a set of parameters for the basis transformation unitary and then provides an example of variational relaxation of the parameters.
Utilities for estimating all quantities described in arXiv:2004.04174 such as fidelities, fidelity witness values, absolute errors, and error bars are also provided.
All software for running the experiment is in the recirq.hfvqe submodule.
The molecular data used in the experiment can be found in the
recirq.hfvqe.molecular_data directory.
Molecular Data
The paper describes the performance of VQE-HF for four hydrogen chain systems and diazene. We provide molecular data files and utilities for generating the hydrogen chain inputs using OpenFermion, Psi4, and OpenFermion-Psi4. The Diazene data can be found in the openfermion-cloud repository. A tutorial on how the data is generated can be found in this ipython notebook.