Strongly driven Josephson circuits for engineering parametric interactions

An outstanding roadblock towards the emergence of large scale quantum devices is the finite lifetime of the underlying qubits. One possible solution is to use a subtle interplay between coherent drives and nonlinear dissipation to protect and manipulate quantum information. This nonlinear dissipation is engineered through parametric methods where a strong off-resonant pump mediates a nonlinear interaction between the system of interest and its bath. The efficiency of this protection scales with the drive strength. In real Josephson circuits, this favorable scaling collapses for a critical drive strength. The purpose of this work is to understand this limitation, and design circuits which circumvent this breakdown. We experimentally investigate the behaviour of two circuit topologies in the presence of strong drives, and discuss the implications for strong qubit readout, and engineered parametric interactions.