“…The competition between strong photon-qubit coupling, giving rise to an effective photonic repulsion (localization), and the photon hopping between cavities (delocalization) leads to a phase diagram featuring Mott lobes reminiscent of those of ultracold atoms in optical lattices as described by the BHM. The realization of the JCHM has been proposed in various solid-state or quantum-optical systems, e.g., with nitrogen-vacancy (NV) centers in diamond [7][8][9], quantum dot excitons [17], superconducting qubits [13], and trapped ions [18]. Device integration, high tunability, and individual addressability of each cavity make wide parameter regimes easily accessible.…”