Extreme Nonlinear Phenomena in NbN Superconducting Stripline Resonators

We study a microwave superconducting stripline resonator made of NbN on a Sapphire wafer. Novel, self-sustained modulation of the reflected power off the resonator, at frequencies of up to 60MHz, has been recently reported. Here we show experimentally that near the self modulation threshold, the device exhibits a giant nonlinearity, which manifests itself in an extremely high intermodulation gain, accompanied by a very strong noise squeezing and period doubling of various orders. Such a device is highly suitable for serving as a readout device in quantum data processing systems.