Wigners friend within a realist toy model


Abstract in English

Wigners gedankenexperiment is often taken as requiring a reassessment of the notion of objective reality. In this note however we present a classical toy model in which (i) The relevant quantum mechanical predictions of Wigners thought experiment are reproduced (ii) Every system is in a well-defined state at all times. The toy model shows how puzzles such as Wigners friends experience of being in a superposition, conflicts between different agents descriptions of the experiment, the positioning of the Heisenbergs cut and the apparent lack of objectivity of measurement outcomes can be explained within a classical model where there exists an objective state of affairs about every physical system at all times. Within the model, the debate surrounding Wigners friend thought experiment and its resolution have striking similarities with arguments concerning the nature of the second law of thermodynamics. The same conclusion however does not straightforwardly apply to more recent extensions of the gedankenexperiment featuring multiple encapsulated observers.

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