Skip to main content

Real or not real that is the question...

Abstract

My discussions with John Bell about reality in quantum mechanics are recollected. I would like to introduce the reader to Bell’s vision of reality which was for him a natural position for a scientist. Bell had a strong aversion against “quantum jumps” and insisted to be clear in phrasing quantum mechanics, his “words to be forbidden” proclaimed with seriousness and wit – both typical Bell characteristics – became legendary. I will summarize the Bell-type experiments and what Nature responded, and discuss the implications for the physical quantities considered, the real entities and the nonlocality concept due to Bell’s work. Subsequently, I also explain a quite different view of the meaning of a quantum state, this is the information theoretic approach, focusing on the work of Brukner and Zeilinger. Finally, I would like to broaden and contrast the reality discussion with the concept of “virtuality,” with the meaning of virtual particle occurring in quantum field theory. With some of my own thoughts I will conclude the paper which is composed more as a historical article than as a philosophical one.

References

  1. 1.

    F. Close,Half life, Oneworld Publication, London, 2015

  2. 2.

    R.A. Bertlmann,Decay modes of ϒ(9.4), ϒ′(10) and their pseudoscalar partners ηq, η′q, Preprint of JINR, E2 - 11029, Dubna (1977)

  3. 3.

    J.J. Sakurai, Phys. Lett. B 46, 207 (1973)

    ADS  Google Scholar 

  4. 4.

    J.S. Bell and R.A. Bertlmann, Z. Phys. C 4, 11 (1980)

    ADS  Google Scholar 

  5. 5.

    J.S. Bell and R.A. Bertlmann, Nucl. Phys. B 177, 218 (1981)

    ADS  Google Scholar 

  6. 6.

    J.S. Bell and R.A. Bertlmann, Nucl. Phys. B 187, 285 (1981)

    ADS  Google Scholar 

  7. 7.

    R.A. Bertlmann and J.S. Bell, Nucl. Phys. B 227, 435 (1983)

    ADS  Google Scholar 

  8. 8.

    J.S. Bell and R.A. Bertlmann, Phys. Lett. B 137, 107 (1984)

    ADS  Google Scholar 

  9. 9.

    A. Einstein, B. Podolsky, and N. Rosen, Phys. Rev. 47, 777 (1935)

    ADS  Google Scholar 

  10. 10.

    J.S. Bell,Bertlmann’s socks and the nature of reality, CERN preprint Ref.TH.2926-CERN (1980)

  11. 11.

    J.S. Bell, J. Phys., Colloque C2, 42, C2 (1981)

    Google Scholar 

  12. 12.

    E. Schrödinger, Brit. J. Phil. Sci. 3, 109, 233 (1952)

    ADS  Google Scholar 

  13. 13.

    J.S. Bell, Are there quantum jumps? inSchrödinger. Cenetary of a polymath, Cambridge University Press, 1987

  14. 14.

    J.S. Bell,Speakable and unspeakable in quantum mechanics, Cambridge University Press, Second Ed., 2004

  15. 15.

    S. Harouche and J.-M. Raimond,Exploring the quantum, Oxford University Press, 2013

  16. 16.

    N. Gisin, Sundays in a quantum engineer’s life, inQuantum [Un]speakables, R.A. Bertlmann and A. Zeilinger (eds.), p. 199, Springer, 2002

  17. 17.

    R.A. Bertlmann and A. Zeilinger (eds.),Quantum [Un]speakables, Springer, 2002

  18. 18.

    J.S. Bell and R. Jackiw, Nuovo Cim. 60, 47 (1969)

    ADS  Google Scholar 

  19. 19.

    S.L. Adler, Phys. Rev. 177, 2426 (1969)

    ADS  Google Scholar 

  20. 20.

    A. Shimony, John S. Bell: some reminiscences and reflections, inQuantum [Un]speakables, R.A. Bertlmann and A. Zeilinger (eds.), p. 51, Springer, 2002

  21. 21.

    J.S. Bell, Physics 1, 195 (1964)

    Google Scholar 

  22. 22.

    A. Einstein, B. Podolsky, and N. Rosen, Phys. Rev. 47, 777 (1935)

    ADS  Google Scholar 

  23. 23.

    D. Bohm,Quantum theory, Prentice-Hall Inc., 1951

  24. 24.

    D. Bohm and Y. Aharonov, Phys. Rev. 108, 1070 (1957)

    ADS  MathSciNet  Google Scholar 

  25. 25.

    J.F. Clauser, M.A. Horne, A. Shimony, and R.A. Holt, Phys. Rev. Lett. 23, 880 (1969)

    ADS  Google Scholar 

  26. 26.

    E.P. Wigner, Am. J. Phys. 38, 1005 (1970)

    ADS  Google Scholar 

  27. 27.

    J.F. Clauser and M.A. Horne, Phys. Rev. D 10, 526 (1974)

    ADS  Google Scholar 

  28. 28.

    P.H. Eberhard, Phys. Rev. A 47, 747 (1993)

    ADS  Google Scholar 

  29. 29.

    R.A. Bertlmann and B.C. Hiesmayr, Phys. Rev. A 63, 062112 (2001)

    ADS  Google Scholar 

  30. 30.

    R.A. Bertlmann, A. Bramon, G. Garbarino, and B.C. Hiesmayr, Phys. Lett. A 332, 355 (2004)

    ADS  Google Scholar 

  31. 31.

    R.A. Bertlmann, W. Grimus, and B.C. Hiesmayr, Phys. Lett. A 289, 21 (2001)

    ADS  Google Scholar 

  32. 32.

    B.C. Hiesmayr, A. Di Domenico, C. Curceanu, A. Gabriel, M. Huber, J-A. Larsson, and P. Moskal, Eur. Phys. J. C 72, 1856 (2012)

    ADS  Google Scholar 

  33. 33.

    A. Bramon and G. Garbarino, Phys. Rev. Lett. 88, 040403 (2002)

    ADS  Google Scholar 

  34. 34.

    A. Bramon and G. Garbarino, Phys. Rev. Lett. 89, 160401 (2002)

    ADS  Google Scholar 

  35. 35.

    H. Tataroglu,Nichtlokale Korrelation in Kaonischen Systemen, Diploma Thesis (in German), University of Vienna, 2009

  36. 36.

    Y.-B. Ding, J.-L. Li, and C.-F. Qiao, High Energy Phys. Nucl. Phys. 11, 1086 (2007)

    Google Scholar 

  37. 37.

    J.-L. Li and C.-F. Qiao, Phys. Lett. A 373, 4311 (2009)

    ADS  Google Scholar 

  38. 38.

    J.-L. Li and C.-F. Qiao, Sci. China G 53, 870 (2010)

    Google Scholar 

  39. 39.

    R.A. Bertlmann, Entanglement, Bell inequalities and decoherence in particle physics, inQuantum coherence: from quarks to solids, W. Pötz, J. Fabian, and U. Hohensteiner (Eds.), Lect. Notes Phys. 689, 1–45, Springer, 2006

  40. 40.

    J.F. Clauser,Early history of Bell’s theorem, in Quantum [Un]speakables, R.A. Bertlmann and A. Zeilinger (eds.), p. 61, Springer, 2002

  41. 41.

    S.J. Freedman and J.F. Clauser, Phys. Rev. Lett. 28, 938 (1972)

    ADS  Google Scholar 

  42. 42.

    S.J. Freedman, LBL Rep. No. 191, Lawrence Berkeley National Laboratory 1972

  43. 43.

    E.S. Fry and R.C. Thompson, Phys. Rev. Lett. 37, 465 (1976)

    ADS  Google Scholar 

  44. 44.

    A. Pais,‘Subtle is the Lord’ ... The Science and Life of Albert Einstein, Oxford University Press, 1982

  45. 45.

    A. Aspect, Phys. Rev. D 14, 1944 (1976)

    ADS  Google Scholar 

  46. 46.

    A. Aspect, P. Grangier, and G. Roger, Phys. Rev. Lett. 47, 460 (1981)

    ADS  Google Scholar 

  47. 47.

    A. Aspect, P. Grangier, and G. Roger, Phys. Rev. Lett. 49, 91 (1982)

    ADS  Google Scholar 

  48. 48.

    A. Aspect, J. Dalibard, and G. Roger, Phys. Rev. Lett. 49, 1804 (1982)

    ADS  MathSciNet  Google Scholar 

  49. 49.

    A. Aspect and P. Grangier, Lett. Nuovo Cim. 43, 345 (1985)

    Google Scholar 

  50. 50.

    R.A. Bertlmann and A. Zeilinger (eds.),Quantum [Un]speakables, Springer, 2016

  51. 51.

    M.A. Nielsen and I.L. Chuang,Quantum computation and quantum information, Cambridge University Press, 2000

  52. 52.

    G. Weihs, T. Jennewein, C. Simon, H. Weinfurter, and A. Zeilinger, Phys. Rev. Lett. 81, 5039 (1998)

    ADS  MathSciNet  Google Scholar 

  53. 53.

    G. Weihs,Ein Experiment zum Test der Bellschen Ungleichung unter Einstein Lokalität, PhD Thesis, University of Innsbruck, 1998

  54. 54.

    J. Brendel, E. Mohler, and W. Martienssen, Europhys. Lett. 20, 575 (1992)

    ADS  Google Scholar 

  55. 55.

    P.R. Tapster, J.G. Rarity, and P.C.M. Owens, Phys. Rev. Lett. 73, 1923 (1994)

    ADS  Google Scholar 

  56. 56.

    W. Tittel, J. Brendel, H. Zbinden, and N. Gisin, Phys. Rev. Lett. 81, 3563 (1998)

    ADS  Google Scholar 

  57. 57.

    K.J. Resch, M. Lindenthal, B. Blauensteiner, H.J. Böhm, A. Fedrizzi, C. Kurtsiefer, A. Poppe, T. Schmitt-Manderbach, M. Taraba, R. Ursin, P. Walther, H. Weier, H. Weinfurter, and A. Zeilinger, Optics Express 13, 202 (2005)

    ADS  Google Scholar 

  58. 58.

    R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, Nat. Phys. 3, 481 (2007)

    Google Scholar 

  59. 59.

    J. Yin, Y. Li, S. Liao, et al., Nature 582, 501 (2020)

    ADS  Google Scholar 

  60. 60.

    D. Rauch, J. Handsteiner, A. Hochrainer, et al., Phys. Rev. Lett. 121, 080403 (2018)

    ADS  Google Scholar 

  61. 61.

    T. Scheidl, R. Ursin, J. Kofler, S. Ramelow, X.-S. Ma, T. Herbst, L. Ratschbacher, A. Fedrizzi, N.K. Langford, T. Jennewein, and A. Zeilinger, Proc. Natl. Acad. Sci. USA 107, 19708 (2010)

    ADS  Google Scholar 

  62. 62.

    M. Giustina, A. Mech, S. Ramelow, B. Wittmann, J. Kofler, J. Beyer, A. Lita, B. Calkins, T. Gerrits, S.W. Nam, R. Ursin, A. Zeilinger, Nature 497, 227 (2013)

    ADS  Google Scholar 

  63. 63.

    M.A. Rowe, D. Kielpinsky, V. Meyer, C.A. Sackett, W.M. Itano, and D.J. Wineland, Nature 409, 791 (2001)

    ADS  Google Scholar 

  64. 64.

    D.N. Matsukevich, P. Maunz, D.L. Moehring, S. Olmschenk, and C. Monroe, Phys. Rev. Lett. 100, 150404 (2008)

    ADS  Google Scholar 

  65. 65.

    G. Kirchmair, F. Zähringer, R. Gerritsma, M. Kleinmann, O. Gühne, A. Cabello, R. Blatt, and C.F. Roos, Nature 460, 494 (2009)

    ADS  Google Scholar 

  66. 66.

    Y. Hasegawa, R. Loidl, G. Badurek, M. Baron, and H. Rauch, Nature 425, 45 (2003)

    ADS  Google Scholar 

  67. 67.

    H. Bartosik, J. Klepp, C. Schmitzer, S. Sponar, A. Cabello, H. Rauch, and Y. Hasegawa, Phys. Rev. Lett. 103, 040403 (2009)

    ADS  Google Scholar 

  68. 68.

    Y. Hasegawa, K. Durstberger-Rennhofer, S. Sponar, and H. Rauch, Kochen-Specker theorem studied with neutron interferometer, arXiv:1004.2836 (2010)

  69. 69.

    M. Giustina, et al., Phys. Rev. Lett. 115, 250401 (2015)

    ADS  Google Scholar 

  70. 70.

    L.K. Shalm, et al., Phys. Rev. Lett. 115, 250402 (2015)

    ADS  Google Scholar 

  71. 71.

    B. Hensen, et al., Nature (London) 526, 682 (2015)

    ADS  Google Scholar 

  72. 72.

    Homepage of the Symposium “Shut up and contemplate!”: https://shutupandcontemplatesymposium.wordpress.com

  73. 73.

    J.S. Bell, The theory of local beables, Epistemological Letters, March 1976, and paper 7, p. 52 inSpeakable and unspeakable in quantum mechanics, J.S. Bell, Cambridge University Press, Second Ed., 2004

  74. 74.

    D. Bohm, Phys. Rev. 85, 166 (1952); ibid p. 180 (1952)

    ADS  MathSciNet  Google Scholar 

  75. 75.

    A. Einstein, Letter to M. Born, May 12th, 1952, inAlbert Einstein Max Born, Briefwechsel 1916–1955, Rowohlt, 1969

  76. 76.

    J. von Neumann,Mathematische Grundlagen der Quantenmechanik, Springer, Berlin 1932 [English translation: Princeton University Press, 1955]

  77. 77.

    J.S. Bell, Rev. Mod. Phys. 38, 447 (1966)

    ADS  Google Scholar 

  78. 78.

    S.B. Kochen and E. Specker, J. Math. Mech. 17, 59 (1967)

    MathSciNet  Google Scholar 

  79. 79.

    J. Conway and S.B. Kochen, The geometry of quantum paradoxes, inQuantum [Un]speakables, R.A. Bertlmann, and A. Zeilinger (eds.), p. 257, Springer, 2002

  80. 80.

    J.S. Bell and W. Walkinshaw,A variational approach to disc loaded waveguides, AERE G/R 680, 1950

  81. 81.

    J.S. Bell and W. Walkinshaw,Review of theory of dielectric loaded linear accelerators, AERE G/R 544, 1950

  82. 82.

    J.S. Bell,Scattering by focussing foils in a proton linear accelerators, AERE T/M 62, 1952

  83. 83.

    J.S. Bell,Phase debunching by focussing foils in a proton linear accelerators, AERE T/M 68, 1952

  84. 84.

    J.S. Bell,Basic algebra of the strong focussing system, AERE T/R 1114, 1953

  85. 85.

    J.S. Bell, La nouvelle cuisine, inBetween Science and Technology, eds. A. Sarlemijn and P. Kroes, Elsevier Science Publishers, 1990

  86. 86.

    R.A. Bertlmann,Bell’s theorem and the nature of reality, preprint University of Vienna 1988, Found. Phys. 20, 1191 (1990)

    ADS  MathSciNet  Google Scholar 

  87. 87.

    A. Zeilinger, Found. Phys. 29, 631 (1999)

    MathSciNet  Google Scholar 

  88. 88.

    Č. Brukner and A. Zeilinger, Phys. Rev. Lett. 83, 3354 (1999)

    ADS  MathSciNet  Google Scholar 

  89. 89.

    Č. Brukner and A. Zeilinger, Phys. Rev. A 63, 022113 (2001)

    ADS  Google Scholar 

  90. 90.

    Č. Brukner and A. Zeilinger, Information and fundamental elements of the structure of quantum theory, inTime, quantum, information, L. Castell and O. Ischebeck (eds.), pp. 323–354, Springer, 2003

  91. 91.

    C.F. von Weizsäcker,Aufbau der Physik, Carl Hanser Verlag, München/Wien, 1985

  92. 92.

    J.A. Wheeler, Information, physics, quantum: the search for links, Proceedings of the IIIrd International Symposium on Foundation of Quantum Mechanics, pp. 354–368, Tokyo, 1989

  93. 93.

    E. Schrödinger, Die gegenwärtige Situation in der Quantenmechanik, Naturwissenschaften 23, 807 (1935)

  94. 94.

    E. Schrödinger, Discussion of probability relations between separated systems, Proc. Cambr. Phil. Soc. 31, 555 (1935); 32, 446 (1936)

    ADS  MATH  Google Scholar 

  95. 95.

    S. Malin, Quantum Information Process. 5, 233 (2006)

    MathSciNet  Google Scholar 

  96. 96.

    Č. Brukner, On the quantum measurement problem, inQuantum [Un]speakables, R.A. Bertlmann and A. Zeilinger (eds.), p. 95, Springer, 2016

  97. 97.

    B. Dakić and Č. Brukner, Quantum theory and beyond: is entanglement special?, inDeep beauty: understanding the quantum world through mathematical innovation, H. Halvorson (ed.), pp. 365–392, Cambridge University Press, 2011, arXiv:0911.0695

  98. 98.

    B. Dakić and Č. Brukner, The classical limit of a physical theory and the dimensionality of space, inQuantum theory: informational foundations and foils, G. Chiribella and R. Spekkens (eds.), pp. 249–282, Springer, 2016, arXiv:1307.3984

  99. 99.

    Č. Brukner, M. Zukowski, and A. Zeilinger,The essence of entanglement, arXiv:0106119

  100. 100.

    E.P. Wigner, Remarks on the mind-body question, inThe scientist speculates, I.J. Good (ed.), pp. 284–302, London, Heinemann, 1961

  101. 101.

    D. Deutsch, Quantum theory as a universal physical theory, Int. J. Theor. Phys. 24, I (1985)

    MathSciNet  Google Scholar 

  102. 102.

    V. Baumann, A. Hansen, and S. Wolf,The measurement problem is the measurement problem is the measurement problem, arXiv:1611.01111

  103. 103.

    V. Baumann and S. Wolf, On formalisms and interpretations, Quantum 2, 99 (2018), arXiv:1710.07212

    Google Scholar 

  104. 104.

    V. Baumann and Č. Brukner, Wigner’s friend as a rational agent, arXiv:1901.1127

  105. 105.

    L. Hardy, Quantum theory from five reasonable axioms, arXiv:quant-ph/0101012

  106. 106.

    R. Clifton, J. Bub, and H. Halvorson, Found. Phys. 33, 1561 (2003)

    MathSciNet  Google Scholar 

  107. 107.

    L. Masanes and M.P. Müller, New J. Phys. 13, 063001 (2011)

    ADS  Google Scholar 

  108. 108.

    G. Chiribella, G.M. D’Ariano, and P. Perinotti, Phys. Rev. A 84, 012311 (2011)

    ADS  Google Scholar 

  109. 109.

    C.A. Fuchs and R. Schack, Rev. Mod. Phys. 85, 1693 (2007)

    ADS  Google Scholar 

  110. 110.

    C.A. Fuchs and R. Schack, QBism and the Greeks: why a quantum state does not represent an element of physical reality, arXiv:1412.4211 (2014)

  111. 111.

    C. Rovelli, Int. J. Theor. Phys. 35, 1637 (1996)

    Google Scholar 

  112. 112.

    F. Horvath,Information theoretical reconstructions of quantum theory, Bachelor Thesis, University of Vienna 2013, https://homepage.univie.ac.at/reinhold.bertlmann, and go to Research/Former Students

  113. 113.

    C. Regner,Information as foundation principle for quantum mechanics, Bachelor Thesis, University of Vienna 2015, https://homepage.univie.ac.at/reinhold.bertlmann, and go to Research/Former Students

  114. 114.

    T. Traxler, Ph.D. Thesis, University of Vienna, 2020

  115. 115.

    T. Aoyama, M. Hayakawa, T. Kinoshita, and M. Nio, Phys. Rev. Lett. 109, 111807 (2012)

    ADS  Google Scholar 

  116. 116.

    D. Hanneke, S. Fogwell Hoogerheide, and G. Gabrielse, Phys. Rev. A 83, 052122 (2011)

    ADS  Google Scholar 

  117. 117.

    H.B.G. Casimir, On the attraction between two perfectly conducting plates, Royal Netherlands Acad. Arts Sci. Proc. 51, 793 (1948); reprinted in Gems from a century of science 1898–1997. Centenary issue of the Proc. of the Royal Netherlands Acad. of Arts and Sciences, L.M. Schoonhoven (eds.), Amsterdam, pp. 61–63 (1997)

    Google Scholar 

  118. 118.

    M. Sparnaay, Nature 180, 334 (1957)

    ADS  Google Scholar 

  119. 119.

    M.J. Sparnaay, Physica 24, 751 (1958)

    ADS  Google Scholar 

  120. 120.

    S.K. Lamoreaux, Phys. Rev. Lett. 78, 5 (1997)

    ADS  Google Scholar 

  121. 121.

    U. Mohideen and Anushree Roy, Phys. Rev. Lett. 81, 4549 (1998)

    ADS  Google Scholar 

  122. 122.

    S. Hawking, Nature 248, 30 (1974)

    ADS  Google Scholar 

  123. 123.

    W.G. Unruh, Phys. Rev. D 14, 870 (1976)

    ADS  Google Scholar 

  124. 124.

    R.A. Bertlmann,Anomalies in quantum field theory, Oxford University Press, 2000

  125. 125.

    R.A. Bertlmann, J. Phys. A: Math. Theor. 47, 424007 (2014)

    ADS  MathSciNet  Google Scholar 

  126. 126.

    R.A. Bertlmann, Bell’s Universe: A Personal Recollection, inQuantum [Un]speakables, R.A. Bertlmann and A. Zeilinger (eds.), p. 17, Springer, 2016

Download references

Acknowledgments

Open access funding provided by University of Vienna.

Author information

Affiliations

Authors

Corresponding author

Correspondence to Reinhold A. Bertlmann.

Additional information

Publisher's Note

The EPJ Publishers remain neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Bertlmann, R.A. Real or not real that is the question.... EPJ H 45, 205–236 (2020). https://doi.org/10.1140/epjh/e2020-10022-x

Download citation