Polaritonic Ground and Excited State Energies on Superconducting Processors*

In polaritonic chemistry, strong light-matter interactions between molecular matter and cavity photons can alter chemical reactions. While classical first-principles approaches exist to describe such systems, their complexity scales exponentially with system size. Quantum algorithms offer a potentially more efficient route toward simulating such systems. In this work, on IBM's superconducting quantum processors, we compute the ground- and excited-state properties of a polaritonic system: H₂ in an optical cavity. To compute ground-state energies, we use the variational quantum eigensolver algorithm with a physically motivated and resource-efficient quantum electrodynamics unitary coupled cluster ansatz [1]. Then, we use the quantum electrodynamics equation-of-motion method to compute excited-state energies and transition dipole moments. By tuning the bond length and light-matter coupling strength, we generate polaritonic potential energy surfaces which can be used for quantum dynamics simulations of polaritonic systems. This work highlights the potential importance of quantum algorithms for polaritonic systems.

[1] F. Pavoševic and J. Flick, J. Phys. Chem. Lett., 12, 37, 9100–9107 (2021).