A strong no-go theorem on the Wigner’s friend paradox

Bong, Kok Wei; Utreras-Alarcón, Aníbal; Ghafari, Farzad; Liang, Yeong-Cherng; Tischler, Nora; Cavalcanti, Eric G.; Pryde, Geoff J.; Wiseman, Howard Mark

doi:10.1038/s41567-020-0990-x

Cited by 111 publications

(322 citation statements)

References 34 publications

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“…If measurement truly collapses a wave function and this results in a recorded fact, then objectivity is guaranteed by the collapse. If instead measurement passes the observer (and his lab) into a superposed state, then experiments such as [11] and [12] begin to seem to question objective reality, while our thought experiment recognizes the actual problem is how to maintain consistency in the complex superposition so that observers or viewers who may encounter each other are in possession of compatible facts. One could in principle hypothesize this directly which essentially was Everett's approach, but instead we have used a hypothesis very similar to some versions of the measurement hypothesis, deliberately so.…”

Section: When Does Quantum Reality Emerge?mentioning

confidence: 93%

“…This roughly replaces consideration #3 in the above list. "Absoluteness" in the sense of [12] is too strong a term for us, since we consider superobservers unable to discuss specific results as not in the same world line as the observers in their experiments. If superpositions exist in the experiment, a world line is an objectively consistent state which is an element of the supeposition.…”

Section: Introductionmentioning

confidence: 98%

“…The observers in the experiments are not conscious of course, consisting of subatomic entities which may not have the freedom to activate the Frauchiger-Renner argument. The next experiment, also using photons, is a proof of concept for a no-go theorem [12] which holds that one of the following must be false:…”

Section: Introductionmentioning

confidence: 99%

“…In the EWFS the superobservers are only allowed to know that the lab observers have a definite result, not what it is. One of the operations permitted the superobservers in [12] is to erase the memory of the lab observers. That would, perhaps surprisingly, only violate our definition of objectivity if it failed to also erase the facts associated with those memories.…”

Section: Introductionmentioning

confidence: 99%

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Emergence of Objective Reality in an Irreversible Friend thought Experiment

Shuler¹

2020

Preprint

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Background: Recently some photon models of a Wigner's friend experiment have led investigators to suggest objective reality does not exist, and to publish non-academic articles with such claims. The public is not equipped to evaluate the severe limitations of these experiments. The separation of Wigner from the experiment and use of only reversible coherent processes for the friend allow operations that are not possible in ordinary reality according to the latest quantum research. Methods: We suggest directly testing the implied claim that objective reality, including incoherent objects with irreversible non-destructive memory, can be held in superposition. We suspect it will fail, but provide for a graduated approach that may discover something about the conditions for superposition collapse. To this end we design a thought experiment to model the objective world, investigating under what conditions experimenters in the same world (ensemble member) will be able to record a result and find it does not appear to change. An observer has a viewing apparatus and a memory apparatus. A second uncorrelated viewer of the same recorded result is employed to obtain objectivity. By hypothesis the uncorrelated second viewer obtains the same view of the measurement record as the first observer. There are not two measurements. This is not an investigation of hidden variables. Results: To model the objective world, incoherent and irreversible processes must be included. To test for superposition, coherence has to be established. These seem to present a contradiction. Conclusions: The thought experiment has suggested new places to look other than size for the origin of objective reality from the quantum world, casts doubt on the Many-Worlds interpretation, and provides a method of testing it.

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Section: When Does Quantum Reality Emerge?mentioning

confidence: 93%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Emergence of Objective Reality in an Irreversible Friend thought Experiment

Shuler¹

2020

Preprint

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“…The paper by Cavalcanti "The View from a Wigner Bubble," then runs with this new Copernican principle to conclude that the outcomes an agent obtains upon a making quantum measurements cannot be considered absolute events in a single spacetime. Differing from usual QBist-style argumentation, his argument is instead based on another recent no-go theorem on the Wigner's friend paradox [18]. The technique is significant in that one does not have be a full-blown QBist to end up at one of QBism's key tenets-the tenet that quantum measurement outcomes must be understood as personal to the agent performing the measurement.…”

mentioning

confidence: 99%

Preface to Special Issue: Quantum Information Revolution: Impact to Foundations

Fuchs

Khrennikov

2020

Found Phys

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The View from a Wigner Bubble

Cavalcanti

2021

Found Phys

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In a recent no-go theorem [Bong et al., Nature Physics (2020)], we proved that the predictions of unitary quantum mechanics for an extended Wigner's friend scenario are incompatible with any theory satisfying three metaphysical assumptions, the conjunction of which we call "Local Friendliness": ABSOLUTENESS OF OBSERVED EVENTS, LOCAL-ITY and NO-SUPERDETERMINISM. In this paper (based on an invited talk for the QBism jubilee at the 2019 Växjö conference 1 ) I discuss the implications of this theorem for QBism, as seen from the point of view of experimental metaphysics. I argue that the key distinction between QBism and realist interpretations of quantum mechanics is best understood in terms of their adherence to different theories of truth: the pragmatist versus the correspondence theories. I argue that a productive pathway to resolve the measurement problem within a pragmatist view involves taking seriously the perspective of quantum betting agents, even those in what I call a "Wigner bubble". The notion of reality afforded by QBism, I propose, will correspond to the invariant elements of any theory that has pragmatic value to all rational agents-that is, the elements that are invariant upon changes of agent perspectives. The classical notion of 'event' is not among those invariants, even when those events are observed by some agent. Neither are quantum states. Nevertheless, I argue that far from solipsism, a personalist view of quantum states is an expression of its precise opposite: Copernicanism.

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A strong no-go theorem on the Wigner’s friend paradox

Cited by 111 publications

References 34 publications

Emergence of Objective Reality in an Irreversible Friend thought Experiment

Emergence of Objective Reality in an Irreversible Friend thought Experiment

Preface to Special Issue: Quantum Information Revolution: Impact to Foundations

The View from a Wigner Bubble

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