Stochastic resonance vs. resonant activation

– The phenomenon of stochastic resonance by which it is possible to boost the transduction of information by tuning into noise is experimentally and numerically contrasted with the phenomenon of resonant activation, i.e. the occurrence of a minimal, averaged residence time at an optimal time-scale in the presence of barrier modulations. The experimental system consists of a periodically modulated bistable colloidal Brownian dynamics. Interestingly enough, the two phenomena may occur simultaneously in the same system, although typically in quite different parameter regimes. The application of a suitable dose of noise can significantly enhance the synchronization of a system’s response to periodic signals. The most intriguing example for this is stochastic resonance (SR) where the response of a nonlinear system to a periodic signal is optimized by the presence of a certain amount of noise [1]. SR is a generic effect and has been experimentally observed in digital devices and an abundance of physical systems [1–6]. In addition, there emerges continuing evidence suggesting the role of SR for intrinsic use and function in biological systems [7]. Another widely studied phenomenon manifesting the constructive role of noise in physical systems is resonant activation (RA) [8–11]. Here, the cooperative interplay between the barrier modulation process and thermal noise assisting barrier crossing events can cause an enhancement of the reaction kinetics. As such, RA is a generic effect for the barrier crossing dynamics of temporally modulated energy landscapes [8–14]. Despite the apparent similarity of SR and RA, it is important to realize a fundamental difference between the two phenomena: While in SR the constructive role of noise is to optimize and synchronize the actual response when metastable states are periodically modulated [1,7] the RA phenomenon maximizes the time-averaged escape rate over a time-modulated energy barrier. Therefore, it is expected that a system’s response to a periodic signal generally cannot be optimized simultaneously for SR and RA, but is either optimized for the strength of the modulated response (at the expense of the transition rate) or for the optimal, shortest mean Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-0-410627 Erschienen in: Europhysics Letters (EPL) ; 74 (2006), 6. S. 937-943 https://dx.doi.org/10.1209/epl/i2006-10052-6