Refuting observer-independence in quantum theory

Massimiliano Proietti, Alexander Pickston, Francesco Graffitti, Peter Barrow, Dmytro Kundys, Cyril Branciard, Martin Ringbauer, Alessandro Fedrizzi

Research output: Chapter in Book/Report/Conference proceedingConference contribution


When Eugene Wigner conceived his Gedankenexperiment in 1961 [1], he argued that in quantum theory two observers, Wigner and his friend, can experience two fundamentally different descriptions of reality. Yet, only six decades later, this question has been rigorously tackled independently by Brukner [2] and Frauchiger and Renner [3], leveraging on the Bell's theorem and on the Hardy's Paradox respectively. They exploit a new extended Wigner's friend scenario, whereby two superobservers (Alice and Bob) and two observers (Alice and Bob's friends) are now entangled, and record their own facts shown to be subjective to the observer who established them.

Original languageEnglish
Title of host publication2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference (CLEO/Europe-EQEC)
ISBN (Electronic)9781728104690
Publication statusPublished - 17 Oct 2019

ASJC Scopus subject areas

  • Spectroscopy
  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Atomic and Molecular Physics, and Optics
  • Computer Networks and Communications


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