Tunneling in rf-SQUIDs and tests of quantum mechanics at the macroscopic level

Superconducting devices such as rf-SQUIDs have been proposed to test the va lidity of quantum mechanics by means of Bell-like inequalities involving di fferent-time correlation probabilities for measurements of magnetic flux. W e calculate the quantum mechanical violations to such temporal Bell inequal ities taking into account the effect of the measurement process on the prob ability distribution for the outcomes. We define a general criterion quanti fying the observability of the violations and show that it is not fulfilled for the various experimental configurations proposed so far.