Diagram driven computer generation of equation-of-motion coupled cluster equations for perturbed quantum oscillators

Abstract

We consider a set of quantum harmonic oscillators subjected to perturbations expressible as a power series in position and momentum. A diagrammatic scheme is developed, by which to generate equation-of-motion coupled cluster (EoM-CC) equations for the calculation of the perturbed energy spectrum of the system. The diagrammatic scheme is then adapted into a Python code, capable of generating the necessary equations and computer code associated with any arbitrary order of the perturbation and coupled cluster excitation levels. The generated equations are made readily accessible for numerical evaluation, alongside convergence schemes and the application of iterative Bogoliubov transformations.