Protection of qubits by nonlinear resonances

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We show that quantized superconducting circuits are non-integrable at the classical level of description, adorned by nonlinear resonances amidst stochastic sea. The stable (elliptic) and unstable (hyperbolic) points occur in a way that by choosing the parameters of a system close to elliptic points, the dynamics is stable. Quantum mechanically, any disturbance has to tunnel the separatrix to reach the elliptic point. Thus, nonlinearity of the system provides protection. Based on these fundamental considerations from the Kolmogorov–Arnold–Moser theorem, we propose criteria for protection of qubits from any disturbance.