  We present an ab initio correlated approach to study molecules that interact
strongly with quantum fields in an optical cavity. Quantum electrodynamics
coupled cluster theory provides a non-perturbative description of
cavity-induced effects in ground and excited states. Using this theory, we show
how quantum fields can be used to manipulate charge transfer and photochemical
properties of molecules. We propose a strategy to lift electronic degeneracies
and induce modifications in the ground state potential energy surface close to
a conical intersection.
