Controlled stochastic amplification of a weak signal in a superconducting quantum interferometer
O.G. Turutanov, V.Yu. Lyakhno
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
V.N. Karazin Kharkiv National University, 4 Svobody sq., Kharkiv 61002, Ukraine
Kyiv Academic University, Kyiv 03142, Ukraine
Received June 26, 2018, published online November 26, 2018
The amplification of a weak low-frequency harmonic signal due to stochastic resonance (SR) effect is observed in a single-junction superconducting quantum interferometer (RF SQUID loop) when quasi-white Gaussian noise magnetic flux is applied to the loop. It is experimentally shown that, at suboptimal flux noise intensity which is insufficient for SR, the mean rate of transitions between the metastable states of the loop, and thus the signal gain, can be controlled by an additional deterministic alternating magnetic flux with frequency being much higher than that of the useful signal to provide the maximal possible gain. The frequency characteristics of a multi-tone composite signal amplification in the cases of controlled stochastic amplification and “pure” stochastic resonance are compared to each other.
Key words: RF SQUID, stochastic resonance, controlled stochastic resonance, ScS contact, Josephson junction.