We propose an information-centric interpretation of quantum mechanics. According to this interpretation, a quantum mechanical system,
A, can always choose a basis in which its own state is an eigenstate; it never sees itself in a superposition. This holds true even if, from the perspective of another system
B,
A is entangled with system
S. In this case,
A and
S are in eigenstates (in their own systems) with their counterpart subsystem wave functions collapsed in the entangled degrees of freedom, but they are entangled according to
B. This interpretation does not introduce new physics, and is consistent with the experimental predictions of quantum mechanics. At the same time, it avoids many ambiguities and potential inconsistencies associated with other interpretations. We further clarify concepts of measurement, macroscopic superposition, entanglement, and the dichotomy between the classical and quantum realms, in accordance with our interpretation.
The aim of this volume is to develop and evaluate the suggestion that if one adopts the interpretation of quantum mechanics initially proposed by Hugh Everett, today frequently referred to as the “many-worlds interpretation,” then one can avoid the kind of nonlocality that is often thought to be a consequence of quantum entanglement according to other approaches, and thus permit the compatibility of these two pillars of modern physics: quantum mechanics and special relativity. Although this is an idea that seems to have been recognized by Everett and is sometimes touted as a reason to prefer his approach to interpreting quantum mechanics over others, the precise way in which Everett’s interpretation achieves this locality, indeed whether it even does achieve locality, has been debated, including among the interpretation’s proponents. The aim of this introductory chapter is to provide readers with a background of this debate concerning the locality of Everettian quantum mechanics. We begin with a brief historical introduction to Everett’s proposed interpretation of quantum mechanics and its later development into the many-worlds interpretation. The following section discusses how the by now well-established phenomenon of quantum entanglement seems to imply what Albert Einstein, in a 1947 letter to Max Born, called “spooky action at a distance,” and a tension with special relativity. We then discuss why one might think that the many-worlds interpretation allows one to avoid nonlocality in this sense. The next sections bring the reader up to date with how the locality of Everettian quantum mechanics has been debated both by critics and proponents of the interpretation. As we will see, the desire to understand Everettian quantum mechanics as an interpretation that avoids nonlocality has opened up some interesting debates concerning both what it means to say an interpretation of quantum mechanics is local and over the metaphysical and mathematical interpretation of Everettian quantum mechanics itself. This introductory chapter concludes with a summary of the contributions to the present volume in the context of this ongoing debate.