Qcombo: A Python Package for Automated Commutator Calculations of Quantum Many-Body Operators

Abstract

qcombo is a Python package for the symbolic evaluation of commutators between general quantum many-body operators expressed in normal-ordered form using the generalized Wick theorem. The package provides an automated and systematic framework for generating the corresponding algebraic expressions, significantly reducing the risk of human error in lengthy and complex analytical derivations. It is designed to assist the development and implementation of modern many-body methods in nuclear physics, quantum chemistry, and related fields. The functionality and workflow of the package are demonstrated through an application to the in-medium similarity renormalization group (IMSRG) method, which has been widely used for nuclear ab initio calculations. As a representative example, qcombo is employed to automatically generate the complete set of multi-reference IMSRG flow equations with operators truncated at the normal-ordered three-body level.

Figures (1)

• Figure 1: Flowchart of the main routine easyCombo in the qcombo package. The workflow includes the construction of commutators, application of contraction rules, regularization of intermediate expressions, simplification of algebraic terms, and generation of outputs in both LaTeX and amc formats.