The observer in the world view of physics

Richard F. Kitchener

Boris Podolsky

Claudia Pombo, Guillaume Adenier, Andrei Yu. Khrennikov +3 more

The realist point of view of a physical theory assumes that physical concepts must have a correspondent in the phenomenological world. We adopt a slightly modified form of realism, based on Carnap's separation of languages, in which only the observational concepts, belonging to the observational language, have a phenomenological correspondent. Other physical concepts, belonging to a theoretical language, do not correspond to entities in the physical world. This point of view is named observational realism. Based on these ideas, we review the notions of relativistic and quantum observation, independently from measurement, and show that there is a discrepancy between the concepts of wave light in relativity and in quantum mechanics.

Lowenstein Jm

Soltau, Andrew

QBism explicitly takes the subjective view: probabilities of events are defined solely by past experiences, i.e. the record of observations. As shown by the authors (Fuchs et al, 2013), this: “... removes the paradoxes, conundra, and pseudo-problems that have plagued quantum foundations for the past nine decades”. It is criticised for its lack of ontology and anthropocentric nature. However, if Everett's (1957) formulation is taken at face value, exactly the features of QBism are the result, and the ontology is inherent. The anthropocentric nature of the solution is simply an indication that the quantum state is relative, as is central to Everett. Problems of measurement and locality do not arise. As described by Tegmark (1997), Everett defines the relationship between two fundamentally different views of the world, different types of frame of reference. The outside view is defined by the unitary wave function, the inside view by the record of observations. As Lockwood (1989) states, the preferred basis problem is fully resolved if the latter is taken as the basis. Taken literally, only that defined by the record of observations is determinate in the physical world of this inside view. The reality of QBism is the result. The same can be derived from first principles in the no-collapse universe. Taking the outside view to define all possible decoherent quasi-classical worlds, the physical world of the inside view is the superposition of all such worlds in which it is instantiated. In this quantum mechanical frame of reference only that observed is determinate. The quantum state as ontology is questioned because it defines only the linear dynamics and cannot account for collapse. No deeper reality is required, however: the inside view, and the collapse dynamics that operates in this type of frame of reference, are emergent properties of the system, and operate at a different level of logical type. The world operates as described by QBism, but is nonetheless defined by the quantum state.

Bruce Rosenblum, Fred Kuttner