# Simulating Molecular Spectroscopy with Circuit Quantum Electrodynamics

## TL;DR

This paper demonstrates that a superconducting quantum simulator can generate molecular spectra for both equilibrium and non-equilibrium states, offering a new approach to understanding molecular spectroscopy through quantum simulation.

## Contribution

It introduces the first experimental use of a superconducting quantum simulator to generate and analyze molecular spectra, including non-equilibrium states and molecules with varied electronic-vibronic coupling.

## Key findings

- Successfully simulated vibronic molecular spectra
- Applicable to molecules with diverse electronic-vibronic coupling
- Accessible spectra not easily obtained in laboratory conditions

## Abstract

Spectroscopy is a crucial laboratory technique for understanding quantum systems through their interactions with electromagnetic radiation. Particularly, spectroscopy is capable of revealing the physical structure of molecules, leading to the development of the maser - the forerunner of the laser. However, real-world applications of molecular spectroscopy are mostly confined to equilibrium states, due to computational and technological constraints; a potential breakthrough can be achieved by utilizing the emerging technology of quantum simulation. Here we experimentally demonstrate that a superconducting quantum simulator is capable of generating molecular spectra for both equilibrium and non-equilibrium states, reliably producing the vibronic structure of the molecules. Furthermore, our quantum simulator is applicable not only to molecules with a wide range of electronic-vibronic coupling strength characterized by the Huang-Rhys parameter, but also to molecular spectra not readily accessible under normal laboratory conditions. These results point to a new direction for predicting and understanding molecular spectroscopy, exploiting the power of quantum simulation.