Experimental Demonstration of Superconducting Metamaterial Nonlinear Resonators With Well-Isolated Modes

The usual linear superconducting resonators (with equal frequency intervals between nearest-neighbor modes) are right-handed electromagnetic devices, wherein crosstalks between the nearest-neighbor modes are practically unavoidable. Here, we demonstrate the nonlinear superconducting metamaterial resonators, wherein frequency intervals between the nearest-neighbor modes are unequal, by using the composite right/left-handed transmission lines. The microwave transport properties are analyzed by the developed real-space approach, instead of the usual equivalent circuit method. The devices are fabricated by using the usual electron beam evaporation technique, and their microwave transport parameters are measured at 50mK-temperature. The observations are basically consistent with the relevant theoretical predictions and also numerical simulations. Hopefully, the demonstrated nonlinear devices, with well-isolated modes could be used to encode the superconducting qubits for microwave quantum information processing.