Towards Quantum Simulation of Chemical Dynamics with Prethreshold Superconducting Qubits

TL;DR

This paper investigates the use of the single excitation subspace (SES) method on superconducting qubits for simulating chemical dynamics, extending classical approaches to lower energies and analyzing computational efficiency for future quantum hardware.

Contribution

It introduces a quantum simulation approach using SES on superconducting qubits for molecular collisions, extending classical methods to lower energies and assessing computational efficiency.

Findings

Classical SCMOCC method extended to lower collision energies.

Feasibility analysis of SES quantum simulation hardware.

Potential for simulating large molecular systems with future quantum processors.

Abstract

The single excitation subspace (SES) method for universal quantum simulation is investigated for a number of diatomic molecular collision complexes. Assuming a system of $n$ tunably-coupled, and fully-connected superconducting qubits, computations are performed in the $n$-dimensional SES which maps directly to an $n$-channel collision problem within a diabatic molecular wave function representation. Here we outline the approach on a classical computer to solve the time-dependent Schr\"odinger equation in an $n$-dimensional molecular basis - the so-called semiclassical molecular-orbital close-coupling (SCMOCC) method - and extend the treatment beyond the straight-line, constant-velocity approximation which is restricted to large kinetic energies ($\gtrsim 0.1$ keV/u). We explore various multichannel potential averaging schemes and an Ehrenfest symmetrization approach to allow for the application of the SCMOCC method to much lower collision energies (approaching 1 eV/u). In addition, a computational efficiency study for various propagators is performed to speed-up the calculations on classical computers. These computations are repeated for the simulation of the SES approach assuming typical parameters for realistic pretheshold superconducting quantum computing hardware. The feasibility of applying future SES processors to the quantum dynamics of large molecular collision systems is briefly discussed.