) scaling (with N electrons/basis functions and N modes cavity modes each with N F Fock states) of the scQED-CC method in general, including more than two Fock states has been a challenge even for small molecular systems, and limited study has been performed including up to 10 Fock states for a half-filled four-site Hubbard model with direct comparison to the full configuration interaction result. This will have unfavorable scaling on multi-mode cavities with quasi-continuous dispersion relations (where N mode > 10). Nevertheless, QED-CCSD remains one of the most accurate approaches for simulating ab initio polaritons. 107