Projects per year
Abstract
In a joint paper Jeff Bub and Itamar Pitowsky argued that the quantum state represents “the credence function of a rational agent […] who is updating probabilities on the basis of events that occur”. In the famous thought experiment designed by Wigner, Wigner’s friend performs a measurement in an isolated laboratory which in turn is measured by Wigner. Here we consider Wigner’s friend as a rational agent and ask what her “credence function” is. We find experimental situations in which the friend can convince herself that updating the probabilities on the basis of events that happen solely inside her laboratory is not rational and that conditioning needs to be extended to the information that is available outside of her laboratory. Since the latter can be transmitted into her laboratory, we conclude that the friend is entitled to employ Wigner’s perspective on quantum theory when making predictions about the measurements performed on the entire laboratory, in addition to her own perspective, when making predictions about the measurements performed inside the laboratory.
Original language  English 

Title of host publication  Quantum, Probability, Logic 
Editors  Meir Hemmo, Orly Shenker 
Publisher  Springer 
Pages  9199 
Number of pages  9 
ISBN (Electronic)  9783030343163 
ISBN (Print)  9783030343156 
DOIs  
Publication status  Published  2020 
Publication series
Series  Jerusalem Studies in Philosophy and History of Science 

ISSN  25244248 
Austrian Fields of Science 2012
 103025 Quantum mechanics
Keywords
 Wigner’s friend
 (Observer) paradox
 Measurement problem
 Interpretations of quantum theory
 Realism
 Subjectivism
Projects
 1 Finished

CoQuS: Complex Quantum Systems
Aspelmeyer, M., Arndt, M. & Paulovics, V.
1/10/07 → 31/12/20
Project: Research funding