Manipulating Two-Photon-Absorption of Cavity Polaritons by Entangled Light

We demonstrate that two-photon excitations to bipolariton states created by placing several molecules in an optical cavity can be manipulated by quantum light. Entangled photons can access classically dark bipolariton states by modifying the quantum interferences of two-photon transition pathways involving different single-polariton intermediate states and time-ordering of the two photon beams.