Classical and quantum stochastic resonance

Speaker: Professor Sue Coppersmith 
Affiliation: University of New South Wales

Abstract

Stochastic resonance, where noise synchronizes a system’s response to an external drive, is a phenomenon that occurs in a wide variety of noisy systems ranging from the dynamics of neurons to the periodicity of ice ages. This talk will introduce stochastic resonance as originally formulated for classical systems, and then present theory and experiments on a quantum system that exhibits stochastic resonance — the quantum tunnelling of the magnetisation of a single Fe atom measured using spin-polarised scanning tunnelling microscopy. Stochastic resonance is shown deep in the quantum regime, where fluctuations are driven by tunnelling of the magnetization, as well as in a semi-classical crossover region where thermal excitations set in. An analytic theory with no adjustable parameters agrees quantitatively with experiment, and provides a path towards probing dynamics on time scales shorter than can be resolved experimentally.