Quantum behavior of underdamped Josephson device

We present an experimental characterization of Nb/AlOx/Nb Josephson devices in the quantum regime. Josephson junctions and fully integrated Josephson devices consisting of an rf SQUID coupled to a read-out system based on a dc SQUID have been measured. Data on the decay rates from the metastable states show evidence of macroscopic quantum tunneling with a very low dissipation level and a high isolation of the devices from the external environment.