Wigner's-friend scenarios
For specified Wigner's-friend protocols, identify which assumptions about record persistence, laboratory coherence and agents' conditioning are operationally testable, and derive robust constraints separating the corresponding models.
Problem statement
For specified Wigner's-friend protocols, identify which assumptions about record persistence, laboratory coherence and agents' conditioning are operationally testable, and derive robust constraints separating the corresponding models.
Lean 4
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Background
In Wigner's-friend scenarios an observer (the friend) performs a measurement inside a sealed lab, while a superobserver (Wigner) treats the whole lab — friend included — unitarily. The two assign different, seemingly incompatible descriptions, raising the question of whether measurement outcomes are absolute or observer-relative.
What is known: Recent no-go theorems have sharpened the puzzle dramatically. Frauchiger–Renner (2018) showed that a set of natural assumptions — that quantum theory applies to agents, that different agents' conclusions can be consistently combined, and that outcomes are single/absolute — are mutually inconsistent, so at least one must be dropped. The Local Friendliness theorem (Bong et al., 2020, with an experiment) derives inequalities from even weaker assumptions ('absoluteness of observed events' plus local agency) and shows quantum mechanics violates them, strictly strengthening Bell's theorem. Various interpretations respond by denying absoluteness (relational QM, QBism, Everett) or agent-independence.
Positive frameworks also exist. Vilasini–Woods formulate extended Wigner's-friend scenarios as quantum circuits, with explicit conditioning on channels and rules for logically and causally consistent agent predictions without absolute measurement events. This preprint framework is not a consensus interpretation or an unrestricted resolution of F1, but invalidates the claim that only no-go theorems are available.
The frontier is experimental and assumption-specific: characterize what records remain accessible when a laboratory is coherently controlled, which agent inferences can be jointly checked, and how noise or imperfect reversibility changes local-friendliness tests. Distinguish actual observation protocols from counterfactual inferences about erased records. Related: F1, F5.
Progress & source assessment
Source catalogue review: 4 September 2026. Improved indicates partial progress, including qualified preprint claims.
preprint: A constructive circuit framework permits logically and causally consistent agent reasoning without absolute events; interpretation-independent experimental discrimination is a separate task. Evidence
- [1]Frauchiger & Renner, 'Quantum theory cannot consistently describe the use of itself', Nat. Commun. 9, 3711 (2018) link
- [2]Bong, Utreras-Alarcón, Ghafari, Liang, Tischler, Cavalcanti, Pryde, Wiseman, 'A strong no-go theorem on the Wigner's friend paradox', Nat. Phys. 16 (2020) link
- [3]Vilasini & Woods, 'A general quantum circuit framework for Extended Wigner's Friend Scenarios: logically and causally consistent reasoning without absolute measurement events', preprint, revised 2024 link
Recorded progress
Add yours →Nothing recorded yet. A pointer to a paper the entry is missing counts.
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