Wigner’s friend thought experiment

E98263

foundational quantum mechanics scenario interpretation-of-quantum-mechanics problem philosophy of physics concept thought experiment

Wigner’s friend thought experiment is a foundational quantum mechanics scenario that explores the role of observers and consciousness in measurement by considering how different observers can assign conflicting quantum states to the same system.

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All labels observed (5)

Label	Occurrences
Wigner’s friend thought experiment canonical	5
Wigner’s friend paradox	2
Schrödinger's cat	1
Wigner's friend thought experiment	1
Wigner’s friend	1

How this entity was disambiguated

This entity first appeared as the object of triple T818203 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.

NED1 Entity disambiguation (via context triple) gpt-5-mini-2025-08-07

Target entity: Wigner’s friend thought experiment
Context triple: [Eugene Wigner, knownFor, Wigner’s friend thought experiment]

A. Maxwell's demon thought experiment
Maxwell's demon thought experiment is a famous conceptual scenario in thermodynamics that imagines an intelligent being seemingly violating the second law by sorting fast and slow gas molecules without expending energy.
B. Bohr–Einstein debates
The Bohr–Einstein debates were a series of famous early 20th-century discussions between Niels Bohr and Albert Einstein about the foundations and interpretation of quantum mechanics, particularly concerning determinism, realism, and the completeness of the theory.
C. Super-many-time theory of quantum mechanics
The Super-many-time theory of quantum mechanics is a relativistic generalization of quantum mechanics that introduces multiple time variables to consistently describe interacting quantum fields in different reference frames.
D. Born rule in quantum mechanics
The Born rule in quantum mechanics is the fundamental postulate that connects a system’s wavefunction to experimentally observed probabilities by stating that measurement outcomes occur with probabilities given by the squared magnitude of the wavefunction’s amplitudes.
E. Mathematical Foundations of Quantum Mechanics
Mathematical Foundations of Quantum Mechanics is John von Neumann’s landmark 1932 treatise that rigorously formulates quantum theory using functional analysis and operator theory on Hilbert spaces.
F. None of above. chosen
G. Unsure - the case is ambiguous/there is not enough information to decide.

NED2 Entity disambiguation (via description) gpt-5-mini-2025-08-07

Target entity: Wigner’s friend thought experiment
Target entity description: Wigner’s friend thought experiment is a foundational quantum mechanics scenario that explores the role of observers and consciousness in measurement by considering how different observers can assign conflicting quantum states to the same system.

A. Maxwell's demon thought experiment
Maxwell's demon thought experiment is a famous conceptual scenario in thermodynamics that imagines an intelligent being seemingly violating the second law by sorting fast and slow gas molecules without expending energy.
B. Bohr–Einstein debates
The Bohr–Einstein debates were a series of famous early 20th-century discussions between Niels Bohr and Albert Einstein about the foundations and interpretation of quantum mechanics, particularly concerning determinism, realism, and the completeness of the theory.
C. Super-many-time theory of quantum mechanics
The Super-many-time theory of quantum mechanics is a relativistic generalization of quantum mechanics that introduces multiple time variables to consistently describe interacting quantum fields in different reference frames.
D. Born rule in quantum mechanics
The Born rule in quantum mechanics is the fundamental postulate that connects a system’s wavefunction to experimentally observed probabilities by stating that measurement outcomes occur with probabilities given by the squared magnitude of the wavefunction’s amplitudes.
E. Mathematical Foundations of Quantum Mechanics
Mathematical Foundations of Quantum Mechanics is John von Neumann’s landmark 1932 treatise that rigorously formulates quantum theory using functional analysis and operator theory on Hilbert spaces.
F. None of above. chosen

Statements (48)

Predicate	Object
instanceOf	foundational quantum mechanics scenario ⓘ interpretation-of-quantum-mechanics problem ⓘ philosophy of physics concept ⓘ thought experiment ⓘ
addresses	objectivity of measurement outcomes ⓘ observer relativity of quantum states ⓘ quantum measurement problem ⓘ
coreIdea	different observers can assign different quantum states to the same physical system ⓘ friend observes a definite outcome while Wigner may still assign a superposed state ⓘ tension between unitary evolution and collapse postulate ⓘ
field	foundations of quantum mechanics ⓘ philosophy of physics ⓘ quantum mechanics ⓘ
hasAuthor	Eugene Wigner ⓘ
hasInterpretationImplicationsFor	collapse theories ⓘ hidden-variable theories ⓘ objective collapse models ⓘ subjective Bayesian interpretations ⓘ
historicalPeriod	20th century ⓘ
involvesConcept	conscious observer ⓘ measurement outcome ⓘ observer-relative state assignment ⓘ superposition ⓘ unitary evolution ⓘ wave function collapse ⓘ
involvesEntity	Wigner ⓘ linked to: Eugene Wigner Wigner’s friend ⓘ linked to: Wigner’s friend thought experiment laboratory isolated from Wigner ⓘ quantum system in a superposition ⓘ
mainTheme	consciousness and quantum measurement ⓘ measurement problem in quantum mechanics ⓘ observer-dependent quantum states ⓘ role of observers in quantum measurement ⓘ
namedAfter	Eugene Wigner ⓘ
proposes	consciousness may play a role in wave function collapse ⓘ
questionRaised	whether all observers must agree on a single set of facts ⓘ whether consciousness is necessary to define measurement outcomes ⓘ whether quantum mechanics is universally valid for observers themselves ⓘ
relatedTo	Copenhagen interpretation ⓘ linked to: Copenhagen interpretation of quantum mechanics Everett many-worlds interpretation ⓘ Frauchiger–Renner paradox ⓘ QBism ⓘ Schrödinger’s cat ⓘ linked to: Schrödinger's cat thought experiment relational quantum mechanics ⓘ
usedInDebatesOn	consistency of quantum theory for multiple observers ⓘ objectivity vs subjectivity of quantum states ⓘ role of consciousness in physics ⓘ status of the wave function ⓘ

How these facts were elicited