SQUID systems for macroscopic quantum coherence and quantum computing

Among the various devices proposed as elements of a quantum computer, the r f-SQUID is a very promising candidate. In fact, systems based on this eleme nt can be adjusted in situ, can be coupled by means of superconducting tran sformers, can be prepared individually and measured with superconducting el ectronics. Moreover, many progresses were made in these years which showed quantum effects in this system. The present paper describes a complete devi ce developed in order to get a direct measurement of the quantum coherent o scillation. The knowledge of this time, together with its limiting factors, is a prerequisite for fabricating a qubit based on rf-SQUIDs.