- Open Access
Boson Sampling Enhanced Quantum Chemistry
PRX Quantum 6, 040357 – Published 5 December, 2025
DOI: https://doi.org/10.1103/gw1c-5b58
Abstract
In this work, we give a hybrid quantum-classical algorithm for solving electronic structure problems of molecules using only linear quantum optical systems. The variational ansatz we proposed is a hybrid of noninteracting boson dynamics and classical computational chemistry methods, specifically, the Hartree-Fock method and the configuration interaction method. The boson part is built by a linear optical interferometer, which is easier to realize compared with the well-known unitary coupled cluster (UCC) ansatz composed of quantum gates in conventional variational quantum eigensolver, and the classical part is merely classical processing acting on the Hamiltonian. The appearance of permanents in the boson part has its physical intuition to provide different kinds of resources from commonly used single, double, and higher excitations in classical methods and the UCC ansatz to explore chemical quantum states. Such resources can help enhance the accuracy of methods used in the classical parts. We give a scalable hybrid homodyne and photon-number measurement procedure for evaluating the energy value, which has intrinsic abilities to mitigate photon loss errors, and discuss the extra measurement cost induced by the no Pauli exclusion principle for bosons with its solutions. To demonstrate our proposal, we run numerical experiments on several molecules and obtain their potential energy curves reaching chemical accuracy.
Physics Subject Headings (PhySH)
Popular Summary
Quantum chemistry aims to predict molecular behavior at the atomic level, essential for innovations in drugs, materials, and energy. Yet, classical computers struggle with the exponential complexity of electron interactions. Quantum computers promise efficiency, but noisy intermediate-scale quantum (NISQ) devices face error and circuit depth challenges. Crucially, how can we harness quantum advantages for chemistry simulations using feasible hardware? And how do we bridge quantum optics with chemical computations to overcome these limits? Addressing these is significant, as it could speed up discoveries by enabling accurate predictions of chemical reactions and molecular properties beyond the reach of classical computing.
We present a hybrid quantum-classical algorithm using passive linear quantum optical systems—known for robust, low-noise photons—to solve electronic potential energy surface problems. Our approach harnesses boson sampling: noninteracting photons traverse a simple linear optical interferometer, generating “permanents,” mathematical objects that offer a unique quantum resource for exploring molecular states. This complements classical methods like Hartree-Fock and configuration interaction, creating a variational ansatz that is experimentally simpler than gate-based circuits.
We devise a scalable hybrid measurement scheme with homodyne and photon-number detectors, inherently mitigating photon losses and handling bosons’ lack of electron-like exclusion rules. Numerical simulations on molecules like lithium hydride and beryllium dihydride yield potential energy curves at chemical accuracy.
This work paves the way for optical quantum advantages in NISQ-era chemistry, inspiring scalable hardware implementations and broader applications in quantum simulation. This method can help experimentalists prioritize the impactful improvements and clarify when photonics should be combined with classical computation to tackle increasingly challenging chemistry.
Article Text
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