Predicting molecular vibronic spectra using time-domain analog quantum simulation

TL;DR

This paper introduces a scalable time-domain analog quantum simulation method for molecular vibronic spectra, demonstrating its effectiveness on a trapped-ion quantum device with accurate results for SO$_2$ spectra.

Contribution

It presents a novel approach for simulating molecular spectra in the time domain using analog quantum simulation, enabling treatment of complex molecules with fewer approximations.

Findings

Successfully simulated SO$_2$ vibronic spectrum with high accuracy

Achieved scalable simulation of complex molecular models

Demonstrated extension to open quantum systems

Abstract

Spectroscopy is one of the most accurate probes of the molecular world. However, predicting molecular spectra accurately is computationally difficult because of the presence of entanglement between electronic and nuclear degrees of freedom. Although quantum computers promise to reduce this computational cost, existing quantum approaches rely on combining signals from individual eigenstates, an approach that is difficult to scale because the number of eigenstates grows exponentially with molecule size. Here, we introduce a method for scalable analog quantum simulation of molecular spectroscopy, by performing simulations in the time domain. Our approach can treat more complicated molecular models than previous ones, requires fewer approximations, and can be extended to open quantum systems with minimal overhead. We present a direct mapping of the underlying problem of time-domain simulation of molecular spectra to the degrees of freedom and control fields available in a trapped-ion quantum simulator. We experimentally demonstrate our algorithm on a trapped-ion device, exploiting both intrinsic electronic and motional degrees of freedom, showing excellent quantitative agreement for a single-mode vibronic photoelectron spectrum of SO$_2$.