Since the purpose of the paper1 in question was to examine the responses to Schrödinger’s cat paradox that are engendered by three particular approaches to quantum mechanics, it is appropriate to comment only on the extent to which the given responses do indeed represent the views of proponents of the various interpretations. For the cases of quantum logic and the many worlds interpretation, I believe that the author has indeed captured the essence of a response that a supporter of that interpretation would give. But I should hope that a supporter of the Copenhagen interpretation would not give the response attributed to him, for it completely misses the point.
Since the purpose of the paper1 in question was to examine the responses to Schrödinger’s cat paradox that are engendered by three particular approaches to quantum mechanics, it is appropriate to comment only on the extent to which the given responses do indeed represent the views of proponents of the various interpretations. For the cases of quantum logic and the many worlds interpretation, I believe that the author has indeed captured the essence of a response that a supporter of that interpretation would give. But I should hope that a supporter of the Copenhagen interpretation would not give the response attributed to him, for it completely misses the point.
The resolutions to the paradox of Schrödinger’s cat engendered by three major perspectives on quantum mechanics—quantum logic, the many worlds interpretation, and the Copenhagen interpretation—are discussed. The core of each perspective is revealed in the process. Each resolution to Schrödinger’s cat has a counterpart which solves the logical paradox known as the unexpected hanging. The rather striking parallels serve to emphasize several points. First, the quantum paradox is an epistemological and not a physical one. Second, the three interpretations mentioned, unlike some others, are faithful to this understanding. And third, the pitfalls in these two paradoxes have a somewhat universal character.
Mainly due to the EPR trio having declared quantum mechanics as ‘not complete’ and given the acid criticisms of Schrödinger, including his famous cat paradox , many physicists felt encouraged to introduce new interpretations to confront a vaguely assembled orthodox interpretation . Indeed, there are numerous interpretations of quantum mechanics, so numerous that we have decided not to even enter into the interpretational arena, leaving that to the professionals and citing their encyclopedic works instead. In this regard, we are compelled to quote Dyson: ‘We still have passionate arguments between believers of various interpretations… The reason for these arguments is that various interpreters are trying to describe the quantum world in words… and the language is inappropriate for the purpose.’ Here, a humble approach to this subject is taken whilst opting for pragmatism.
For many years the physical interpretation of quantum theory has been dominated by the “wave-particle duality” attitude of the “Copenhagen school.” This point of view is eloquently described in Bohr's collection of essays on the subject. Despite persistent concerns with apparent paradoxes and limitations to this interpretation (as exemplified by Schrodinger's cat, the paradox of Einstein, Podolsky and Rosen, among others), the Copenhagen view persists de facto in the daily life of the modern physicist. Traditional quantum theory has so successfully explained such a vast amount of data in atomic and molecular physics, solid state physics (and to a lesser extent, elementary particle physics) that little doubt can exist concerning its essential validity. As a consequence of the overwhelming practical success of the “Copenhagen interpretation, ” the latter has acquired the status of dogma. For many years, therefore, most physicists have found it expedient to relegate the puzzling aspects of the theory to philosophers, and mathematicians. Nevertheless, a persistent interest in this subject has produced a significant and fascinating literature, reviewed by Jammer. In recent years, concerns over the proper meaning to be ascribed to quantum theory have produced an increasingly deep and incisive series of investigations. These investigations fall generally into two categories: either (1) discussion of the philosophical content of the theory, or (2) analyses of the mathematical variants of the theory and their connection with differing interpretational schemes. Physicists tend to be detached from a commitment to philosophical issues, because of their realization of the transient character of the meanings attached to theories of the day. As a simple illustration of this we can mention the profound differences between nonrelativistic and relativistic quantum mechanics.
Long ago, and almost in parallel with the “orthodox” Copenhagen/standard interpretation, other interpretations of quantum mechanics were proposed. Giving an exhaustive discussion of all points of view that have been put forward since then would probably be an impossible task. Moreover, while one can distinguish big families among the interpretations, it is also possible to combine them in many ways, with an almost infinite number of nuances. The Copenhagen/standard interpretation itself, as we have seen, is certainly not a monolithic construction, but can be declined in various forms. In this chapter, we will therefore limit ourselves to a general description of the major families of interpretations. We will begin with a brief description of some frequent attitudes observed among scientists in laboratories, who do not necessarily pay extreme attention to the foundations of quantum mechanics, even when they do experiments in quantum physics. In practice, they often use pragmatic rules, which are sufficient to interpret all their experiments, and prefer to avoid difficult questions about the very nature of the measurement process. For instance, one popular point of view is the “correlation interpretation”, which can be considered as a “minimal interpretation” – minimal but sufficient for all practical purposes; it is accepted as a valid rule by a large majority of physicists, even those who prefer to supplement it with other elements in order to reach a more precise interpretation for the whole theory. We will then proceed to discuss various families of interpretations that are less common, including additional variables, modified Schrödinger dynamics, consistent histories, Everett interpretation, etc.
The purpose of this paper is to resolve two paradoxes, which occur in quantum theory, by using the discussion of the theory of measurement presented in two earlier papers by the author [3], [4], [5]. The two paradoxes discussed will be the Schrödinger cat paradox and the Einstein, Podolski, Rosen paradox [2]. An introductory section will be included which summarizes the relevant results from the author's previous papers. Also a discussion will be made regarding the author's interpretation of the density operator.