Bridging chemistry and Gaussian boson sampling: A photonic hierarchy of approximations for molecular vibronic spectra

TL;DR

This paper explores how photonic approximations can efficiently simulate molecular vibronic spectra, showing that Gaussian boson sampling is not always necessary and proposing a hierarchy of methods.

Contribution

It establishes a hierarchy of photonic approximations for vibronic spectra, linking traditional chemistry methods with photonic implementations, and demonstrates experimental improvements for specific molecules.

Findings

Photonic hierarchy can outperform GBS in simulating spectra for certain molecules.

Linear coupling approximation corresponds to sampling from multiple coherent states.

Experimental results show improved similarity scores for formic acid.

Abstract

Simulating vibronic spectra is a central task in physical chemistry, offering insight into important properties of molecules. Recently, it has been experimentally demonstrated that photonic platforms based on Gaussian boson sampling (GBS) are capable of performing these simulations. However, whether an actual GBS approach is required depends on the molecule under investigation. To develop a better understanding on the requirements for simulating vibronic spectra, we explore connections between theoretical approximations in physical chemistry and their photonic counterparts. Mapping these approximations into photonics, we show that for certain molecules the GBS approach is unnecessary. We place special emphasis on the linear coupling approximation, which in photonics corresponds to sampling from multiple coherent states. By implementing this approach in experiments, we demonstrate improved similarities over previously reported GBS results for formic acid and identify the particular attributes that a molecule must exhibit for this, and other approximations, to be valid. These results highlight the importance in forming deeper connections between traditional methods and photonic approaches.