A recent study revealed how different methods for simulating molecular vibrations - important for understanding how molecules absorb and emit light – map to various light-based simulators with varying complexity. Jan-Lucas Eickmann and colleagues conducted the work in collaboration with HQS Quantum Simulations as part of the PhoQuant project. The research was led by Dr. Michael Stefszky and Prof. Christine Silberhorn at the Institute of Photonic Quantum Systems (PhoQS) at the University of Paderborn.
Their study demonstrates that optical simulators can replicate traditional computational chemistry methods in a highly structured and predictable way. They’ve shown that there is a „ladder“ of light-based simulation methods, with each step corresponding to well-known approximation techniques from chemistry, known as linear coupling (or linear), parallel and Duschinsky approximations.
Even with the simplest version of the presented light-based simulator schemes (i.e. linear coupling) they successfully reproduced the spectral signatures of several molecules in experiments and compared their measurements to numerical simulations of the more sophisticated light-based simulation methods, i.e. parallel and Duschinsky approximations. „I was surprised to see that many molecules can already be described sufficiently well using the simpler linear coupling approach. We’ve achieved a high experimental fidelity by avoiding the squeezing and interferometer imperfections, and compensating for optical losses” commented Jan-Lucas on the results.
Beyond showing that many molecules are already well modelled with the simplest approach, the researchers also identified molecules that genuinely require more advanced photonic simulators. By strengthening this interdisciplinary understanding the researchers hope to find new, exciting possible use cases for light-based simulators.
J.-L. Eickmann, et al., Bridging chemistry and Gaussian boson sampling: a photonic hierarchy of approximations for molecular vibronic spectra, npj Quantum Information (2026); DOI: https://doi.org/10.1038/s41534-026-01250-x
