Measurements of thermal switching between metastable flux states in a rf-SQUID with intermediate damping.

Josephson devices and, in particular, RF-SQUIDs are ideal systems to test quantum phenomena at macroscopic level. In the view of an experiment of macroscopic quantum coherence, as a preliminary test we developed and fabricated on the same chip a set of thin-film RF-SQUIDs shunted with thin-film resistors of different values, to investigate the behavior of the RF-SQUIDs in different dissipation regimes. Here we present measurements on a moderately damped RF-SQUID, shunted with an 11 ? resistor. In function of the temperature, we recorded the RF-SQUID characteristics (total magnetic flux vs applied magnetic flux) and studied the statistical distribution of the flux values at which the RF-SQUID switches from one metastable flux state to another. The RF-SQUID is read-out by a DC-SQUID integrated on the same chip.