Nonlinear physics in superconducting microwave circuits

Abstract

The use of superconducting microwave circuits, known for their extremely low losses, has been widespread in observing various physical phenomena. Particularly in the era of quantum computing, superconducting microwave resonators play a crucial role in reading and controlling superconducting qubits. Additionally, optoemchanical systems dealing with the interaction between microwave photons in superconducting circuits and nanomechanical oscillators play a significant role in quantum sensing and quantum transduction. However, research on the nonlinearity of superconducting circuits has not received as much attention. We observed interesting phenomena in the nonlinearity of superconducting microwave circuits, such as the frequency grid phenomenon observed in niobium-based microwave optical components. Furthermore, by utilizing the fact that the dynamic inductance of a superconducting microwave resonator changes with superconducting quasi-particles, we demonstrated the effective tuning of microwave resonance frequencies by applying electric gate voltages in titanium nitride-based superconducting microwave resonators.