Improving quality by noise

Stochastic resonance can be observed when moderated noise added to a bi-stable system helps to detect a weak signal (i.e., to increase the signal-to-noise ratio). For lower noise intensities, the signal does not cause the device to cross threshold, so little signal is passed through it. For large noise intensities, the output is dominated by the noise, also leading to a low signal-to-noise ratio. For moderate intensities, the noise allows the signal to reach threshold, but the noise intensity is not so large as to swamp it. This effect manifest itself in different physical and biological systems, including neuron system, solid state systems, the earth's orbit cycles, or even old photos restoration (see above images).

It is commonly accepted that stochastic resonance required three basic components:

• an energetic activation barrier
• a weak coherent input
• noise

In the recently published work [1], Dr. S. Saveliev and collaborators have shown that stochastic resonance can be induced merely by geometrical properties of the system without involvement of any energetic barrier whatsoever.

This opens a new avenue for applications of the stochastic resonance to a broader class of physical systems. For instance, now Dr. Saveliev, his MSc student Mr R. Glavey and Dr. M. Gaifullin work on the realization of the stochastic resonance in superconducting vortex systems.

 
[1] P.K. Ghosh, F. Marchesoni, S.E. Savel’ev, and Franco Nori, Phys. Rev. Lett 104, 020601 (2010).