Spectroscopy of the modes of a non-linear superconducting microwave resonator via inter-mode coupling and bifurcation amplification

Abstract

The Josephson non-linearity provides a route to high sensitivity measurements through the bifurcation of a resonant mode into two metastable dynamical states. We probe the bifurcation regime of a superconducting microwave co-planar resonator incorporating a controlled non-linearity made of an array of SQUIDs. The switching probability between metastable states may be determined by repeated measurements under nominally identical conditions. We show that measurements of this probability and the inter-mode coupling introduced by the SQUIDs may be used for spectroscopy of other resonant modes. We also find the width of the switching-curve is within a factor two of quantitative agreement with Dykman's model, but that the switching probability is affected by a low frequency noise that has its source on-chip.