# Quantum simulation of molecular spectroscopy in trapped-ion device

## TL;DR

This paper reports the first experimental demonstration of molecular vibrational spectroscopy using a trapped-ion quantum system, showcasing a promising approach for large-scale quantum simulations of complex molecules.

## Contribution

It experimentally implements a molecular spectroscopic process in a trapped-ion system using Gaussian transformations, advancing quantum simulation capabilities.

## Key findings

- Successful reconstruction of molecular spectroscopic signals
- Implementation of multimode Gaussian transformations via Raman lasers
- Paves the way for large-scale quantum molecular simulations

## Abstract

Molecules are the most demanding quantum systems to be simulated by quantum computers because of their complexity and the emergent role of quantum nature. The recent theoretical proposal of Huh et al. (Nature Photon., 9, 615 (2015)) showed that a multi-photon network with a Gaussian input state can simulate a molecular spectroscopic process. Here, we report the first experimental demonstration of molecular vibrational spectroscopy of SO$_{2}$ with a trapped-ion system. In our realization, the molecular scattering operation is decomposed to a series of elementary quantum optical operations, which are implemented through Raman laser beams, resulting in a multimode Gaussian (Bogoliubov) transformation. The molecular spectroscopic signal is reconstructed from the collective projection measurements on phonon modes of the trapped-ion system. Our experimental demonstration would pave the way to large-scale molecular quantum simulations, which are classically intractable.