  An amplification of a weak low-frequency harmonic signal is experimentally
observed in a single-junction-superconducting quantum interferometer (RF SQUID
loop) due to stochastic transitions between two or more metastable states of
the loop under the applied noise flux of varying intensity (the effect of
stochastic resonance, SR). In addition to the usual scenario of the SR in a
bistable system with Gaussian noise, the transitions between multiple
metastable states of the multi-well SQUID loop potential under the influence of
a binary noise is observed. This can be interpreted as a kind of noise
"spectroscopy" of the metastable states of the SQUID loop with different values
of the trapped magnetic flux.
