Agreement and Compatibility in Wigner's Friend Paradox
Abstract
There has been an upsurge of interest in the consequences for quantum physics of the so-called Wigner's Friend Paradox. In its original formulation, the paradox has been turned inside out, and virtually every aspect of it has been looked into. Consequently, it is becoming widely accepted that we can find the potentially puzzling consequences of Wigner's thought experiment only in light of its many-parties extensions. Nonetheless, this contribution returns to the source. Reframing the question as an inference problem, we advance a radically Bayesian interpretation that shows no contradiction between Wigner's and Wigner's Friend's descriptions---neither classically nor quantumly. Therefore, with no paradoxical conclusion. In doing so, we flesh out and expose previously untouched aspects of Wigner's thought experiment, in particular, the fact that compatibility and agreement are fundamental to our understanding of it, and that a rigorous notion of compatibility is the key to paving the way for the agents to reach an agreement. Also, by conservatively extending Wigner's original setup and incorporating what we call the 'benefit of the doubt', we see how either Wigner's or his Friend's description can be driven to match one another's---an impossibility if either agent does not keep an open mind.
Versions
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BibTeX
@misc{silva2026agreement,
title = {{Agreement and Compatibility in Wigner's Friend Paradox}},
author = {Julio C. F. Silva and B. F. Rizzuti and Cristhiano Duarte},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2605.27424},
eprint = {2605.27424},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.27424},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Agreement and Compatibility in Wigner's Friend Paradox
AU - Julio C. F. Silva
AU - B. F. Rizzuti
AU - Cristhiano Duarte
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2605.27424
UR - https://arxiv.org/abs/2605.27424
AB - There has been an upsurge of interest in the consequences for quantum physics of the so-called Wigner's Friend Paradox. In its original formulation, the paradox has been turned inside out, and virtually every aspect of it has been looked into. Consequently, it is becoming widely accepted that we can find the potentially puzzling consequences of Wigner's thought experiment only in light of its many-parties extensions. Nonetheless, this contribution returns to the source. Reframing the question as an inference problem, we advance a radically Bayesian interpretation that shows no contradiction between Wigner's and Wigner's Friend's descriptions---neither classically nor quantumly. Therefore, with no paradoxical conclusion. In doing so, we flesh out and expose previously untouched aspects of Wigner's thought experiment, in particular, the fact that compatibility and agreement are fundamental to our understanding of it, and that a rigorous notion of compatibility is the key to paving the way for the agents to reach an agreement. Also, by conservatively extending Wigner's original setup and incorporating what we call the 'benefit of the doubt', we see how either Wigner's or his Friend's description can be driven to match one another's---an impossibility if either agent does not keep an open mind.
ER -