Quantum Simulation of Realistic Materials in First Quantization Using Non-local Pseudopotentials

TL;DR

This paper advances quantum algorithms for electronic structure simulation by incorporating pseudopotentials, enabling more efficient and accurate modeling of realistic materials, including non-cubic unit cells and catalysis scenarios.

Contribution

It introduces the first quantum algorithm for first quantized simulation that accurately includes pseudopotentials, improving efficiency for realistic material simulations.

Findings

Pseudopotentials reduce the number of plane waves needed for accuracy.

Block encoding of pseudopotentials can be achieved without significant cost increase.

First quantization often requires less computational resources than second quantization for large systems.

Abstract

This paper improves and demonstrates the usefulness of the first quantized plane-wave algorithms for the quantum simulation of electronic structure, developed by Babbush et al. and Su et al. We describe the first quantum algorithm for first quantized simulation that accurately includes pseudopotentials. We focus on the Goedecker-Tetter-Hutter (GTH) pseudopotential, which is among the most accurate and widely used norm-conserving pseudopotentials enabling the removal of core electrons from the simulation. The resultant screened nuclear potential regularizes cusps in the electronic wavefunction so that orders of magnitude fewer plane waves are required for a chemically accurate basis. Despite the complicated form of the GTH pseudopotential, we are able to block encode the associated operator without significantly increasing the overall cost of quantum simulation. This is surprising since simulating the nuclear potential is much simpler without pseudopotentials, yet is still the bottleneck. We also generalize prior methods to enable the simulation of materials with non-cubic unit cells, which requires nontrivial modifications. Finally, we combine these techniques to estimate the block-encoding costs for commercially relevant instances of heterogeneous catalysis (e.g. carbon monoxide adsorption on transition metals) and compare to the quantum resources needed to simulate materials in second quantization. We conclude that for computational cells with many particles, first quantization often requires meaningfully less spacetime volume.