Principles and Lessons of Quantum Physics. A Review of Interpretations, Mathematical Formalism, and Perspectives

Abstract

In the previous chapters we used the standard language of quantum theory. We have extensively used the terms “observable” in the sense of Dirac’s book of 1930 and “state” in the sense of von Neumann’s book of 1932. This language implies an essential resignation as compared to the “classical” ideal of the scope of physics prevailing before the advent of quantum mechanics. Eminent physicists, among them Planck, Einstein, and Schrodinger did not accept this resignation as unavoidable. Over 60 years have passed since the great debates. We have witnessed fundamental new discoveries, an enormous growth of knowledge, and the development of the theory from non-relativistic quantum mechanics to relativistic quantum field theories with applications ranging from laboratory experiments in high energy physics to cosmology. Yet, with a few minor modifications and changes in emphasis the standard language remained viable and no alternative of comparable usefulness has been created. Nevertheless some measure of dissatisfaction or at least an uneasiness that something is missing in the standard picture persisted throughout the years and is even more acutely felt today. The large amount of literature devoted to the interpretation of quantum mechanics bears witness to this. It therefore seems useful to review the main arguments advanced during this long-lasting dispute, trying to sharpen the points at issue, and to assess the strengths and weaknesses of various points. This will be attempted in section VII.1. Another matter is the specific mathematical structure of quantum physics.