Laszlo E. Szabo

“In an earlier era of ‘natural philosophy’, physics and philosophy of physics were quite inseparably intertwined, but in the modern age of proliferating specialization, fruitful communication across the disciplines has become the exception rather than rule. We would like to think that the workshop1 and this volume are symptomatic of an ongoing process of reunification, one which can pave the way toward exceptional progress in this fundamental and highly challenging area, and others as well” — the editors Richard A. Healey and Geoffrey Hellman write in the Preface. The main topic of the ten articles in this volume, Quantum Measurement, indeed, requires both physical and philosophical considerations

The aim of this paper is to provide an introduction to Fine's interpretation of quantum mechanics and to show how it can solve the EPR-Bell problem. In the real spin-correlation experiments the detection/emission inefficiency is usually ascribed to independent random detection errors, and treated by the “enhancement hypothesis.” In Fine's interpretation the detection inefficiency is an effect not only of the random errors in the analyzer + detector equipment, but is also the manifestation of a pre-settled (hidden) property of the particles. I present one of Fine's 2×2 prism models for the EPR experiment and compare it with the recent experimental results. In the second part of the paper I prove the existence of a wide class of n×n prism models with reasonable detection/emission efficiencies, satisfying the usually required symmetries. Contrary to the common persuasion, the efficiencies in these models do not necessarily tend to zero if n→∞

In 1935, Einstein, Podolsky, and Rosen (EPR) published an important paper in which they claimed that the whole formalism of quantum mechanics together with what they called a “Reality Criterion” imply that quantum mechanics cannot be complete. That is, there must exist some elements of reality that are not described by quantum mechanics. They concluded that there must be a more complete description of physical reality involving some hidden variables that can characterize the state of affairs in the world in more detail than the quantum mechanical state. This conclusion leads to paradoxical results. As Bell proved in 1964, under some further but quite plausible assumptions, this conclusion that there are hidden variables implies that, in some spin-correlation experiments, the measured quantum mechanical probabilities should satisfy particular inequalities (Bell-type inequalities). The paradox consists in the fact that quantum probabilities do not satisfy these inequalities. And this paradoxical fact has been confirmed by several laboratory experiments since the 1970s. Some researchers have interpreted this result as showing that quantum mechanics is telling us nature is non-local, that is, that particles can affect each other across great distances in a time too brief for the effect to have been due to ordinary causal interaction. Others object to this interpretation, and the problem is still open and hotly debated among both physicists and philosophers. It has motivated a wide range of research from the most fundamental quantum mechanical experiments through foundations of probability theory to the theory of stochastic causality as well as the metaphysics of free will.