Quantum Mechanics and Its Interpretations: A Defense of the Quantum Principles

Michele Caponigro

Eamonn F. Healy

Although the presentation of quantum mechanics found in traditional textbooks is intellectually well founded, it suffers from a number of deficiencies. Specifically introducing quantum mechanics as a solution to the arcane dilemma, the ultraviolet catastrophe, does little to impress a nonscientific audience of the tremendous paradigmatic shift that quantum mechanics represented. Mathematical descriptions of the wave function can also fail to impart to the audience the true nature of the quantum measurement problem and its implications for our concept of reality. Presenting both Bell’s theorem and Heisenberg’s uncertainty principle in a heuristic framework allows for a conceptual-based discussion of quantum phenomena suitable for a mathematically naïve undergraduate or an interested nonscientist.

L. E. Ballentine

Jeffrey Bub

Ishwar S Singh, M. A. B. Whitaker

Raffael Krismer

Contemporary non-representationalist interpretations of the quantum state (especially QBism, neo-Copenhagen views, and the relational interpretation) maintain that quantum states codify observer-relative information. This paper provides an extensive defense of such views, while emphasizing the advantages of, specifically, the relational interpretation. The argument proceeds in three steps: (1) I present a classical example (which exemplifies the spirit of the relational interpretation) to illustrate why some of the most persistent charges against non-representationalism have been misguided. (2) The special focus is placed on dynamical evolution. Non-representationalists often motivate their views by interpreting the collapse postulate as the quantum mechanical analogue of Bayesian probability updating. However, it is not clear whether one can also interpret the Schrödinger equation as a form of rational opinion updating. Using results due to Hughes & van Fraassen as well as Lisi, I argue that unitary evolution has a counterpart in classical probability theory: in both cases (quantum and classical) probabilities relative to a non-participating observer evolve according to an entropy maximizing principle (and can be interpreted as rational opinion updating). (3) Relying on a thought-experiment by Frauchiger and Renner, I discuss the differences between quantum and classical probability models.