Chaos measurements in Josephson tunnel junctions

On the experimental side, the presence of chaos is detected by measuring the noise it produces; so far, many authors have performed such measurements, consistent with expectations for chaotic noise. They also reveal features which are not explained on the basis of chaos. The cause of this discrepancy is discussed and other experimental features are reported. The authors conclude it should be recalled that by incorporating thermal noise into numerical simulations, besides confirming the existence of a strong noise rise due to thermal induced hopping, found what is called thermal induced chaos, i.e. the existence of truly choatic states is periodic when the thermal noise is removed. The coexistence of at least three intrinsic mechanisms (strict chaos, thermal induced chaos and thermal induced hopping) greatly complicates the experimental investigation of the noise rise in such a system so that frequency and temperature dependence of the noise levels are required to sort out the presence of different mechanisms