The Significance of the MQC Experiment

It is generally agreed that quantum mechanics (QM) describes brilliantly the behavior of matter at the atomic and subatomic level. However, many people, including the author, believe that if it is taken seriously at the level of everyday life, it leads to insuperable difficulties, exemplified by the fate of Schrödinger's unfortunate cat. If, therefore, one is prepared to envisage seriously the possibility that if QM is pushed sufficiently far it may break down or have to be supplemented by some new and currently unforeseeable principle, then the obvious axis along which to try to "push" it is that which brings us closest to the world of everyday life. Thus, we are motivated to try to define which exact feature most sharply distinguishes those applications of QM at the everyday level that appear paradoxical: to seek, in fact, a quantitative measure of the degree of "Schrödinger's-cattiness" of various physical situations. Although this is no doubt a subjective question, I explore two plausible candidates: one involving the divergence, in the two branches of the (notional) quantum superposition, of some "macroscopic" physical quantity; the other invoking the idea of "disconnectivity" - a notion that has much in common with the concept of "degree of entanglement" currently employed in the context of EPR-Bell-type experiments. Having tried to isolate and define the "axis" along which we are trying to push QM, I then discuss the main generic obstacles to this program, which may be summarized as (1) quasi-classicality, (2) decoherence, and (3) Franck-Condon suppression. Finally, I emphasize the importance not only of verifying (or not) that QM continues to predict correctly the experimental behavior as we progress along the relevant axis, but of confronting its predictions with those of a class of alternative, "macrorealistic" theories. I comment on the implications of various possible outcomes to this confrontation.