Stochastic Resonance with a Single Metastable State

TL;DR

This paper investigates thermal instability and stochastic resonance in NbN superconducting resonators, revealing how nonlinearity near bifurcation points enhances weak signals and is limited by thermal relaxation rates.

Contribution

It provides experimental and theoretical analysis of metastable state lifetimes and signal amplification near bifurcation in superconducting resonators.

Findings

Strong amplification of weak signals near bifurcation.

Bandwidth limited by thermal relaxation rate.

Sub-harmonics appear at high input modulation frequencies.

Abstract

We study thermal instability in NbN superconducting stripline resonators. The system exhibits extreme nonlinearity near a bifurcation, which separates a monostable zone and an astable one. The lifetime of the metastable state, which is locally stable in the monostable zone, is measure near the bifurcation and the results are compared with a theory. Near bifurcation, where the lifetime becomes relatively short, the system exhibits strong amplification of a weak input modulation signal. We find that the frequency bandwidth of this amplification mechanism is limited by the rate of thermal relaxation. When the frequency of the input modulation signal becomes comparable or larger than this rate the response of the system exhibits sub-harmonics of various orders.