Figure 2From: Nonlinearity and nonclassicality in a nanomechanical resonator State fidelity \(\pmb{F(\varepsilon)}\) between the ground state of the undriven Duffing oscillator achieved through a perturbative approach \(\pmb{\vert \psi_{0} \rangle }\) and that estimated numerically by diagonalising the Hamiltonian model in Eq. ( 2 ) using the first 51 number states. Back to article page