Figure 4

The coherent excitation number{\mathit{n}}_{\mathbf{2}}\mathbf{=}{\mathbf{|}{\mathit{\alpha }}_{\mathbf{2}}\mathbf{|}}^{\mathbf{2}}in the second transmission line resonator as a function of the nonlinearity\mathit{U}\mathbf{/}\mathit{\gamma }and the tunneling rate\mathit{J}\mathbf{/}\mathit{\gamma }for in-phase laser input\mathit{\phi }\mathbf{=}\mathbf{0}and\mathbf{\Omega }\mathbf{/}\mathit{\gamma }\mathbf{=}\mathbf{5}. Stronger drives lead to even higher excitation numbers n_2.