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Updated: Oct 28, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Intracavity photon statistics from correlated molecular electronic structure
1Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA.
Abstract:
Quantum optics characterizes light through photon correlations, motivating their connection to correlated ab initio molecular electronic structure. In this study, intracavity photon statistics of cavity-coupled molecules are computed from QED coupled-cluster (QED-CCSD-22) densities and validated against exact diagonalization of the Pauli-Fierz Hamiltonian. A change of coordinate origin or dipole convention displaces the ground state coherently, so second-order and higher cumulants of the cavity field are independent of these conventions even for molecular ions. The photon subsystem of QED Hartree-Fock is exactly coherent, so the invariant statistics describe fluctuations beyond this electron-photon product reference. The field fluctuations are super-Poissonian, and their degree of second-order coherence depends primarily on cavity frequency in the tested weak-coupling regime, falling from 18.5 to 4.9 for H2 as the cavity is detuned from 5 to 20 eV. The third cumulant identifies non-Gaussian fluctuations and changes sign under reversal of the coupling direction.
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