Perspectives of an experiment for detecting macroscopic quantum coherence

In the second half of 1993 we presented to INFN a proposal of an experiment for detecting macroscopic quantum coherence with a system of SQUIDs. It was based essentially on ideas presented first by Leggett and collaborators and developed in many articles in the 1980s. The experimental work started in the 1994 just after the approval of the INFN. As an introduction, the experimental method and the setup we choose in order to perform a set of measurements on a system of SQUIDs is described. Then the measuring procedures and their purposes are explained and discussed. As a future perspective, a possible test on the existence of the quantum gravity is discussed. According to a theoretical proposal by John Ellis and collaborators, the quantum gravitational "friction" could induce the transition from QM behavior of microscopic states to the classical behavior of macroscopic states, i.e., states containing an Avogadro number (M-pl/M-e) of elementary particles, as may be obtained in a SQUID.