Macroscopic quantum effects in Josephson systems

Macroscopic quantum effects in Josephson systems have attracted great inter est in the scientific community both for the physics involved and in view o f applications. We present data on macroscopic quantum tunneling on Josephs on junctions. Actually the most fashinating topic is the observation of mac roscopic quantum coherence in rf-SQUID, This effect also has implications f or quantum computing, because a quantum two-state system represents a singl e quantum bit, which is the elementary unit of a quantum computer, In this context, here we present a new method to measure quantum coherence between different fluxoid states of an rf-SQUID by using the procedure of "adiabati c inversion". This method offers the possibility of measuring tunneling and dechoerence times in the system.