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 cross talks 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 50 mK 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.