Macroscopic quantum effects in Josephson systems

Macroscopic quantum effects in Josephson systems have attracted great interest in the scientific community both for the physics involved and in view of applications. We present data on macroscopic quantum tunneling on Josephson junctions. Actually the most fascinating topic is the observation of macroscopic quantum coherence in rf-SQUID. This effect also has implications for quantum computing, because a quantum two-state system represents a single 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 "adiabatic inversion". This method offers the possibility of measuring tunneling and decoherence times in the system.