Figure 8

Ratio of quantum fluctuations to the coherent background excitation number for the mid-resonator,$\mathbf{〈}{\stackrel{\mathbf{ˆ}}{\mathit{\delta }\mathit{a}}}_{\mathbf{2}}^{\mathbf{†}}{\stackrel{\mathbf{ˆ}}{\mathit{\delta }\mathit{a}}}_{\mathbf{2}}\mathbf{〉}\mathbf{/}\mathbf{|}{\mathit{\alpha }}_{\mathbf{2}}{\mathbf{|}}^{\mathbf{2}}$as a function of$\mathit{J}\mathbf{/}\mathit{\gamma }$and$\mathit{U}\mathbf{/}\mathit{\gamma }$in the strong driving regime with$\mathbf{\Omega }\mathbf{/}\mathit{\gamma }\mathbf{=}\mathbf{5}$. For higher drives Ω the ratio becomes smaller and also stays small up to larger nonlinearities U.