OBSERVATION OF QUANTUM COHERENCE BY MEANS OF TEMPORAL BELL-TYPE INEQUALITIES

Violation of temporal Bell inequalities, based on the premises of real ism and non-invasive measurability, provides a criterion for exhibitin g macroscopic quantum coherence. Although the experimental refutation of this kind of inequality is extremely difficult when macroscopic sys tems are involved, we can get some insight into the problem by studyin g systems at an intermediate scale. In this case, the non-invasive mea surability assumption does not hold; the inhibition of dynamics for co ntinuous monitoring (quantum Zeno effect) is one consequence of this. However, directly testable Bell-type inequalities can be derived if on e replaces the non-invasive measurability assumption by a stationarity condition. Accordingly to a realist approach, such inequalities shoul d hold for any (strictly) two-state stochastic process. Here Ne propos e an experimental situation where violations of such inequalities may possibly be observed.