Grid-based methods for chemistry simulations on a quantum computer

TL;DR

This paper demonstrates the feasibility of grid-based quantum chemistry simulations using emulated quantum computers with up to 36 qubits, exploring various algorithms for atomic modeling and dynamics.

Contribution

It introduces resource-efficient algorithms for first quantized chemistry simulations on quantum computers, including novel techniques within the split-operator QFT framework.

Findings

Grid-based methods perform well in emulated quantum simulations.

Various algorithms successfully model atomic ground states and dynamics.

First quantized approaches are promising for early fault-tolerant quantum computing.

Abstract

First quantized, grid-based methods for chemistry modelling are a natural and elegant fit for quantum computers. However, it is infeasible to use today's quantum prototypes to explore the power of this approach, because it requires a significant number of near-perfect qubits. Here we employ exactly-emulated quantum computers with up to 36 qubits, to execute deep yet resource-frugal algorithms that model 2D and 3D atoms with single and paired particles. A range of tasks is explored, from ground state preparation and energy estimation to the dynamics of scattering and ionisation; we evaluate various methods within the split-operator QFT (SO-QFT) Hamiltonian simulation paradigm, including protocols previously-described in theoretical papers as well as our own novel techniques. While we identify certain restrictions and caveats, generally the grid-based method is found to perform very well; our results are consistent with the view that first quantized paradigms will be dominant from the early fault-tolerant quantum computing era onward.