Ab initio quantum dynamics using coupled-cluster

TL;DR

This paper introduces OATDCC, a novel polynomially scaling, size-consistent, and extensive method for simulating quantum dynamics of many-particle systems by generalizing coupled-cluster techniques to the time domain with adaptive orbitals.

Contribution

It develops the orbital-adaptive time-dependent coupled-cluster (OATDCC) method, extending coupled-cluster to quantum dynamics with adaptive orbitals, improving scalability and flexibility.

Findings

OATDCC inherits size-consistency and extensivity from CC.

The method provides a hierarchy of approximations to multi-configurational time-dependent Hartree.

Numerical experiments demonstrate the method's effectiveness.

Abstract

The curse of dimensionality (COD) limits the current state-of-the-art {\it ab initio} propagation methods for non-relativistic quantum mechanics to relatively few particles. For stationary structure calculations, the coupled-cluster (CC) method overcomes the COD in the sense that the method scales polynomially with the number of particles while still being size-consistent and extensive. We generalize the CC method to the time domain while allowing the single-particle functions to vary in an adaptive fashion as well, thereby creating a highly flexible, polynomially scaling approximation to the time-dependent Schr\"odinger equation. The method inherits size-consistency and extensivity from the CC method. The method is dubbed orbital-adaptive time-dependent coupled-cluster (OATDCC), and is a hierarchy of approximations to the now standard multi-configurational time-dependent Hartree method for fermions. A numerical experiment is also given.