The Extended Wigner’s Friend thought experiment, comprising a quantum system containing an agent who draws conclusions upon observing the outcome of a measurement of a quantum state prepared in two nonorthogonal versions by another agent, led its authors to conclude that quantum theory cannot consistently describe the use of itself. It has also been proposed that this thought experiment is equivalent to entangled state (Bell-type) experiments. It is argued in this paper that the assumption of the freedom of choice of the first Wigner’s friend regarding how to prepare a quantum state in one of the two available nonorthogonal versions invalidates such equivalence.
References
[1]
Renner, D.F.R. (2016) Single-World Interpretations of Quantum Theory Cannot Be Self-Consistent.
[2]
Renner, D.F.R. (2018) Quantum Theory Cannot Consistently Describe the Use of Itself. Nature Communications, 9, Article No. 3711.
https://doi.org/10.1038/s41467-018-05739-8
[3]
Elitzur, A.C. and Vaidman, L. (1993) Quantum Mechanical Interaction-Free Measurements. Foundations of Physics, 23, 987-997.
https://doi.org/10.1007/BF00736012
[4]
Blaylock, G. (2010) The EPR Paradox, Bell’s Inequality, and the Question of Locality. American Journal of Physics, 78, 111-120. https://doi.org/10.1119/1.3243279
[5]
Brukner, Č. (2015) On the Quantum Measurement Problem. Springer, Cham.
https://doi.org/10.1007/978-3-319-38987-5_5
[6]
Brukner, Č. (2018) A No-Go Theorem for Observer-Independent Facts. Entropy, 20, 350. https://doi.org/10.3390/e20050350
[7]
Proietti, M., et al. (2019) Experimental Test of Local Observer Independence. Science Advances, 5, eaaw9832. https://doi.org/10.1126/sciadv.aaw9832
[8]
Bong, K.-W., Utreras-Alarcon, A., Ghafari, F., Liang, Y.-C., Tischler, N., Cavalcanti, E.G., Pryde, G.J. and Wiseman, H.M. (2019) Testing the Reality of Wigner’s Friend’s Experience. https://doi.org/10.1117/12.2540002
[9]
Wigner, E. (1961) The Scientist Speculates. 284-302.
[10]
Deutsch, D. (1985) Quantum Theory as a Universal Physical Theory. International Journal of Theoretical Physics, 24, 1-41. https://doi.org/10.1007/BF00670071
[11]
Sudbery, A. (2019) The Hidden Assumptions of Frauchiger and Renner. The International Journal of Quantum Foundations, 5, 98.
[12]
Bub, J. (2017) Why Bohr Was (Mostly) Right.
[13]
Kwiat, P. and Hardy, L. (2000) The Mystery of the Quantum Cakes. American Journal of Physics, 68, 33-36. https://doi.org/10.1119/1.19369
[14]
Kastner, R.E. (2020) Unitary-Only Quantum Theory Cannot Consistently Describe the Use of Itself: On the Frauchiger-Renner Paradox. Foundations of Physics, 50, 441-456. https://doi.org/10.1007/s10701-020-00336-6
[15]
Shuler, R.L. (2021) Emergence of Objective Reality in an Irreversible Friend Thought Experiment. Journal of Applied Mathematics and Physics, 9, 1964-1977.
https://doi.org/10.4236/jamp.2021.98128
[16]
Sudbery, A. (2017) Single-World Theory of the Extended Wigner’s Friend Experiment. Foundations of Physics, 47, 658-669. https://doi.org/10.1007/s10701-017-0082-7
[17]
Baumann, V., Hansen, A. and Wolf, S. (2016) The Measurement Problem Is the Measurement Problem Is the Measurement Problem.
[18]
Lazarovici, D. and Hubert, M. (2019) How Quantum Mechanics Can Consistently Describe the Use of Itself. Scientific Reports, 9, Article No. 470.
https://doi.org/10.1038/s41598-018-37535-1
[19]
Muciño, R. and Okon, E. (2020) Wigner’s Convoluted Friends. Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 72, 310. https://doi.org/10.1016/j.shpsb.2020.07.001
[20]
Tausk, D.V. (2018) A Brief Introduction to the Foundations of Quantum Theory and an Analysis of the Frauchiger-Renner Paradox.
[21]
Cabello, A., Gu, M., Gühne, O., Larsson, J.-Å. and Wiesner, K. (2016) Thermodynamical Cost of Some Interpretations of Quantum Theory. Physical Review A, 94, Article ID: 052127. https://doi.org/10.1103/PhysRevA.94.052127
[22]
Deutsch, D. (1996) Comment on Lockwood. British Journal for the Philosophy of Science, 47, 222-228. https://doi.org/10.1093/bjps/47.2.222
[23]
Fuchs, C.A. (1998) Just Two Nonorthogonal Quantum States. Quantum Communication, Computing, and Measurement, 2, 11-16.
https://doi.org/10.1007/0-306-47097-7_2