Quantum mechanics versus macroscopic realism: Is the flux there when nobody looks?

Abstract

It is shown that, in the context of an idealized ``macroscopic quantum coherence'' experiment, the predictions of quantum mechanics are incompatible with the conjunction of two general assumptions which are designated ``macroscopic realism'' and ``noninvasive measurability at the macroscopic level.'' The conditions under which quantum mechanics can be tested against these assumptions in a realistic experiment are discussed.