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Register a new userA no-go theorem for the persistent reality of Wigners friends perception
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Added by
Philippe Allard Gu\\'erin
Publication date
2020
fields
Physics
and research's language is
English
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The notorious Wigners friend thought experiment (and modifications thereof) has in recent years received renewed interest especially due to new arguments that force us to question some of the fundamental assumptions of quantum theory. In this paper, we formulate a no-go theorem for the persistent reality of Wigners friends perception, which allows us to conclude that the perceptions that the friend has of her own measurement outcomes at different times cannot share the same reality, if seemingly natural quantum mechanical assumptions are met. More formally, this means that, in a Wigners friend scenario, there is no joint probability distribution for the friends perceived measurement outcomes at two different times, that depends linearly on the initial state of the measured system and whose marginals reproduce the predictions of unitary quantum theory. This theorem entails that one must either (1) propose a nonlinear modification of the Born rule for two-time predictions, (2) sometimes prohibit the use of present information to predict the future -- thereby reducing the predictive power of quantum theory -- or (3) deny that unitary quantum mechanics makes valid single-time predictions for all observers. We briefly discuss which of the theorems assumptions are more likely to be dropped within various popular interpretations of quantum mechanics.
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