The Relational Interpretation of Quantum Mechanics

Matteo Smerlak

Jay Lawrence, Marcin Markiewicz, Marek Żukowski

Relational Quantum Mechanics (RQM) claims to be an interpretation of quantum theory \cite{Rovelli.21}. However, there are significant departures from quantum theory: (i) in RQM measurement outcomes arise from interactions which entangle a system S and an observer A without decoherence, and (ii) such an outcome is a "fact" relative to the observer A , but it is not a fact relative to another observer B who has not interacted with S or A during the foregoing measurement process. For B the system S⊗A remains entangled. We derive a GHZ-like contradiction showing that relative facts described by these statements are incompatible with quantum theory. Hence Relational Quantum Mechanics should not be considered an interpretation of quantum theory, according to a criterion for interpretations that we have introduced. The criterion states that whenever an interpretation introduces a notion of outcomes, these outcomes, whatever they are, must follow the probability distribution specified by the Born rule.

Giovanni Buonocore

Abstract The present paper aims to provide an insight into the epistemological and metaphysical implications of a structuralist interpretation of Relational Quantum Mechanics (RQM). I will suggest that the ‘entity‐relation identity’ at the core of a particular formulation of Ontic Structural Realism represents the best framework against which to understand RQM, and, in turn, that this interpretation provides some support for the adoption of a structuralist viewpoint in Quantum Mechanics thus understood. The choice is motivated by the same revisionary metaphysics they both seem to offer, with respect to the notion of entity and of relation.

Carlo Rovelli C

Gary Gordon

The relational interpretation of quantum mechanics (RQM), introduced in its present form by Carlo Rovelli in 1996, involves a number of significant departures from other QM interpretations widely discussed in the literature. We begin here by summarizing these unique RQM features, with a focus on those that suggest altered insights into the nature of the randomness exhibited in QM phenomena. One of these RQM features is the assumption that all objects in the universe are quantum objects, regardless of their material complexity. And, the interaction of any two objects can result in new relational quantum states of each of the objects with the other as reference. But such new states do not replace relational states corresponding to previous interactions with other reference objects. In particular, such earlier relational states that include a variable considered to be random do not collapse to define a determined value of the variable, but instead simply take on that specific value in the state relative to the new reference. The concept of randomness associated with quantum state variables in RQM thus differs from that in other QM interpretations. Rather than take the usual pedantic approach of elaborate side-by-side comparisons between the RQM and other common QM interpretations, we illustrate these differences by describing in some detail the well-known "dual-slit" experiment in terms of RQM concepts, pointing out the important advantages over other interpretations along the way. Of course, we suggest no change in dual-slit experiment results, but believe that the interpretative modifications are helpful and profound.