Qcombo: A Python Package for Automated Commutator Calculations of Quantum Many-Body Operators
arXiv:2603.24399
The paper introduces Qcombo, a Python package that automates symbolic commutator calculations for quantum many-body operators using the generalized Wick theorem, and demonstrates its use in generating IMSRG flow equations up to three-body normal ordering.
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.
17 pages with 1 figure