Bifurcation, mode coupling and noise in a nonlinear multimode superconducting RF resonator

TL;DR

This paper explores a superconducting nonlinear resonator using Josephson junctions, demonstrating bifurcation amplification and mode spectroscopy, with results approaching quantum model predictions but limited by on-chip noise.

Contribution

It introduces a tunable nonlinear superconducting resonator that enables bifurcation amplification and mode coupling spectroscopy, advancing quantum microwave device capabilities.

Findings

Sensitivity close to quantum model predictions

Demonstrated mode coupling spectroscopy

Noise source identified as on-chip

Abstract

The addition of nonlinearity to an harmonic resonator provides a route to complex dynamical behaviour of resonant modes, including coupling between them. We present a superconducting device that makes use of the nonlinearity of Josephson junctions to introduce a controlled, tunable, nonlinear inductance to a thin film coplanar waveguide resonator. Considering the device as a potential quantum optical component in the microwave regime, we create a sensitive bifurcation amplifier and then demonstrate spectroscopy of other resonant modes via the intermode coupling. We find that the sensitivity of the device approaches within a factor two quantitative agreement with a quantum model by Dykman, but is limited by a noise that has its source(s) on-chip.