Document Type

Article

Publication Date

7-15-2019

Abstract

The production of events in quantum theory, that is, of outcomes to which a probability can be associated, is inconsistent with a unitary evolution for systems in arbitrary initial states. In particular, within unitary quantum mechanics, there exist global protocols that allow verifying that no definite event occurs. Instead, states that start in a coherent superposition over possible outcomes always remain as a superposition. We show that when taking into account fundamental errors in measuring length and time intervals, which have been put forward as a consequence of a conjunction of quantum mechanical and general relativity arguments, there are instances in which such global protocols no longer allow one to distinguish whether or not the state is in a superposition. All predictions become identical as if one of the outcomes occurs, with probability determined by the state. We use this as a criteria to define events, as put forward in the Montevideo interpretation of quantum mechanics. We analyze in detail the occurrence of events in the paradigmatic case of a particle in a superposition of two different locations. We argue that our approach provides a consistent (C) single-world (S) picture of the universe, thus allowing an economical way out of the limitations imposed by a recent theorem by Frauchiger and Renner showing that having a self-consistent single-world description of the universe is incompatible with quantum theory. In fact, the main observation of this paper may be stated as follows: If quantum mechanics is extended to include gravitational effects to a quantum-gravitational (QG) theory, then QG, S, and C are satisfied.

Publication Source (Journal or Book title)

Physical Review A

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