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Wigner’s friend and relational objectivity

Nature Reviews Physics volume 4, pages 628–630 (2022)Cite this article

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The ‘Wigner’s friend’ thought experiment illustrates the puzzling nature of quantum measurement. Časlav Brukner discusses how recent results suggest that in quantum theory the objectivity of measurement outcomes is relative to observation and observer.

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Fig. 1: Illustration of the two ‘bubbles’: the laboratory of Wigner’s friend and that of Wigner.

References

  1. Wigner, E. P. Remarks on the mind-body question. In The Scientist Speculates (ed. Good, I. J.) 284–302 (Heinemann, 1961).

  2. Brukner, Č. On the quantum measurement problem. In Quantum[Un]Speakables II: Half a Century of Bell’s Theorem (eds Bertlmann, R. & Zeilinger, A.) 95–117 (Springer, 2017).

  3. Frauchiger, D. & Renner, R. Quantum theory cannot consistently describe the use of itself. Nat. Commun. 9, 3711 (2018).

    Article  ADS  Google Scholar 

  4. Brukner, Č. A no-go theorem for observer-independent facts. Entropy 20, 350 (2018).

    Article  ADS  MathSciNet  Google Scholar 

  5. Bong, K. W. et al. A strong no-go theorem on the Wigner’s friend paradox. Nat. Phys. 16, 1199–1205 (2020).

    Article  Google Scholar 

  6. Proietti, M. et al. Experimental test of local observer independence. Sci. Adv. 5, eaaw9832 (2019).

    Article  ADS  Google Scholar 

  7. Fuchs, C. A. & Schack, R. Quantum-Bayesian coherence. Rev. Mod. Phys. 85, 1693 (2013).

    Article  ADS  Google Scholar 

  8. Rovelli, C. Relational quantum mechanics. Int. J. Theor. Phys. 35, 1637–1678 (1996).

    Article  MathSciNet  Google Scholar 

  9. Healey, R. The Quantum Revolution in Philosophy (Oxford University Press, 2017).

  10. Cavalcanti, E. G. The view from a Wigner bubble. Found. Phys. 51, 39 (2021).

    Article  ADS  MathSciNet  Google Scholar 

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  1. Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences and Faculty of Physics, University of Vienna, Vienna, Austria

    Časlav Brukner

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  1. Časlav Brukner
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Correspondence to Časlav Brukner.

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Brukner, Č. Wigner’s friend and relational objectivity. Nat Rev Phys 4, 628–630 (2022). https://doi.org/10.1038/s42254-022-00505-8

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