Symmetry-based perturbation theory for electronic structure calculations

TL;DR

This paper introduces a symmetry-based perturbation theory for electronic structure calculations that leverages Hamiltonian symmetries to improve computational efficiency and accuracy in quantum chemistry.

Contribution

It develops a multi-reference perturbation framework based on Hamiltonian symmetries, enhancing efficiency and robustness over existing methods.

Findings

SBPT reduces computational resources compared to traditional methods.

It provides scalable solutions for second-order corrections.

SBPT yields improved results for certain molecular systems.

Abstract

We develop a multi-reference perturbation theory for electronic structure calculations based on symmetries of the Hamiltonian. The reference Hamiltonian in the symmetry-based perturbation theory (SBPT) is chosen such that it possesses more symmetries than the original Hamiltonian, leading to a larger reduction of computational resources in terms of both the number of configurations in the configuration interaction expansion and the number of required qubits in quantum computing applications. We provide approximate, scalable solutions for the second-order correction, as well as an application to selected configuration interaction. We show that SBPT is an extension of other existing multi-reference perturbation theories and that it can give better results for some molecular systems in a robust way.