Skip to main content Accessibility help

Quantum entanglement: facts and fiction – how wrong was Einstein after all?

  • Bengt Nordén (a1)


Einstein was wrong with his 1927 Solvay Conference claim that quantum mechanics is incomplete and incapable of describing diffraction of single particles. However, the Einstein-Podolsky-Rosen paradox of entangled pairs of particles remains lurking with its ‘spooky action at a distance’. In molecules quantum entanglement can be viewed as basis of both chemical bonding and excitonic states. The latter are important in many biophysical contexts and involve coupling between subsystems in which virtual excitations lead to eigenstates of the total Hamiltonian, but not for the separate subsystems. The author questions whether atomic or photonic systems may be probed to prove that particles or photons may stay entangled over large distances and display the immediate communication with each other that so concerned Einstein. A dissociating hydrogen molecule is taken as a model of a zero-spin entangled system whose angular momenta are in principle possible to probe for this purpose. In practice, however, spins randomize as a result of interactions with surrounding fields and matter. Similarly, no experiment seems yet to provide unambiguous evidence of remaining entanglement between single photons at large separations in absence of mutual interaction, or about immediate (superluminal) communication. This forces us to reflect again on what Einstein really had in mind with the paradox, viz. a probabilistic interpretation of a wave function for an ensemble of identically prepared states, rather than as a statement about single particles. Such a prepared state of many particles would lack properties of quantum entanglement that make it so special, including the uncertainty upon which safe quantum communication is assumed to rest. An example is Zewail's experiment showing visible resonance in the dissociation of a coherently vibrating ensemble of NaI molecules apparently violating the uncertainty principle. Einstein was wrong about diffracting single photons where space-like anti-bunching observations have proven recently their non-local character and how observation in one point can remotely affect the outcome in other points. By contrast, long range photon entanglement with immediate, superluminal response is still an elusive, possibly partly misunderstood issue. The author proposes that photons may entangle over large distances only if some interaction exists via fields that cannot propagate faster than the speed of light. An experiment to settle this ‘interaction hypothesis’ is suggested.

  • View HTML
    • Send article to Kindle

      To send this article to your Kindle, first ensure is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

      Note you can select to send to either the or variations. ‘’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

      Find out more about the Kindle Personal Document Service.

      Quantum entanglement: facts and fiction – how wrong was Einstein after all?
      Available formats

      Send article to Dropbox

      To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

      Quantum entanglement: facts and fiction – how wrong was Einstein after all?
      Available formats

      Send article to Google Drive

      To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

      Quantum entanglement: facts and fiction – how wrong was Einstein after all?
      Available formats


This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.

Corresponding author

*Author for Correspondence: B. Nordén, Chair Professor of Physical Chemistry, Chalmers University of Technology, SE-41296 Gothenburg, Sweden. E-mail:


Hide All
Ardavan, A, Rival, O, Morton, J. L., Blundell, S., Tyryshkin, , Timco, G. A. & Winpenny, E. P. (2007). Will spin relaxation in molecular magnets permit quantum information processing? Physical Review Letters 98, 5720157204.
Aspect, A., Dalibard, J. & Roger, G. (1982a). Experimental test of Bell's inequalities using time-varying analyzers. Physical Review Letters 49, 18041807.
Aspect, A., Grangier, P. & Roger, G. (1982b). Experimental realization of Einstein-Podolsky-Rosen-Bohm Gedankenexperiment: a new violation of Bell's inequlities. Physical Review Letters 49, 9194.
Atkins, P. W., McLauchlan, J. & Percival, P. W. (1973). Electron spin-lattice relaxation times from the decay of e.s.r. emission spectra. Molecular Physics 25, 281296.
Ballentine, L. E. (1970). The statistical interpretation of quantum mechanics. Reviews of Modern Physics 42, 358381.
Basché, T. H., Moerner, W. E., Orrit, M. & Talon, H. (1992). Photon antibunching in the fluorescence of a single dye molecule trapped in a solid. Physical Review Letters 69, 15161519.
Bayer, M., Hawrylak, P., Hinzer, K., Fafard, S., Korkusinsky, M., Wasilewki, Z. R., Stern, O. & Forchel, A. (2000). Coupling and entangling of quantum states in quantum dot molecules. Science 291, 451453.
Bell, J. S. (1966). On the problem of hidden variables in quantum mechanics. Reviews of Modern Physics 38, 447452.
Bennett, C. H., Brassard, G., Crepenau, C., Jozsa, R., Peres, A. & Wootters, W. K. (1993). Teleporting an unknown quantum state via dual classical and Einstein-Podolsky-Rosen channels. Physical Review Letters 70, 18952001.
Blatt, R. & Wineland, D. (2008). Entangled states of trapped atomic ions. Nature 453, 10081015.
Bogani, L. & Wernsdorfer, W. (2008) Molecular spintronics using single-molecule magnets. Nature Materials 7, 179186.
Bohm, D. (1952). A suggested interpretation of the quantum theory in terms of hidden variables. Physical Review 85, 166179.
Bohm, D. & Aharonov, Y. (1957) Discussion of experimental proof for the paradox of Einstein, Podolsky and Rosen. Physical Review 108, 10701076.
Bohr, N. (1935a). Can quantum-mechanical description of physical reality be considered complete? Physical Review 48, 696702.
Bohr, N. (1935b). Quantum mechanics and physical reality. Nature 136, 6565.
Bransden, B. H. & Joachain, C. (2000). Quantum Mechanics, 2nd edn, pp. 769770. New York: Prentice Hall.
Carg, A. & Mermin, N. D. (1987). Detector inefficiencies in the Einstein-Podolsky-Rosen experiment. Physical Review D 35, 38313835.
Choi, K. S., Deng, H., Laurat, J. & Kimble, H. J. (2008) Mapping photonic entanglement into and out of quantum memory. Nature 452, 6771.
Clauser, J. F. & Horne, M. A. (1974). Experimental consequences of objective local theories. Physical Review D 10, 526535.
Clauser, J. F. & Shimony, A. (1978). Bell's theorem: experimental tests and implications. Reports on Progress in Physics 41, 18811927.
Clauser, J. F., Horne, M. A., Shimony, A. & Holt, R. A. (1969). Proposed experiment to test local hidden-variable theories. Physical Review Letters 23, 880884.
Cowen, R. (2015). Space. Time. Entanglement. Nature 527, 290293.
Dirac, P. A. M. (1926). On the theory of quantum mechanics. Proceedings of the Royal Society of London, Series A 112, 661677.
Duan, L-M., Giedke, G., Cirac, J. I. & Zoller, P. (2000). Entanglement purification of Gaussian continuous variable quantum states. Physical Review Letters 84, 40024005.
Eberhart, P. H. (1989) Quantum Theory and Pictures of Reality, pp. 169216. Berlin: Springer.
Einstein, A. (1936). Physik und Realität. Journal of Franklin Institute 221, 313347.
Einstein, A. & Rosen, N. (1935). The particle problem in the general theory of relativity. Physical Review 48, 7377.
Einstein, A., Podolsky, B. & Rosen, N. (1935). Can quantum-mechanical description of physical reality be considered complete? Physical Review 47, 770780.
Ekert, A. (1991). Quantum cryptography based on Bell's theorem. Physical Review Letters 67, 661663.
Engel, V., Metiu, H., Almeida, R., Marcus, R. A. & Zewail, A. H. (1988). Molecular state evolution after excitation with an ultra-short laser pulse. A quantum analysis of NaI and NaBr dissociation. Journal of Chemical Physics 90, 61166128.
Epstein, R. J., Mendoza, F. M., Kato, Y. K. & Awschalom, D. D. (2005). Anisotropic interactions of single spin and dark-spin spectroscopy in diamond. Nature Physics 1, 9498.
Franson, J. D. (1989) Bell inequality for position and time. Physical Review Letters 62, 22052208.
Freedman, S. J. & Clauser, J. F. (1972). Experimental test of local hidden variable theories. Physical Review Letters 28, 938941.
Friberg, S. R., Hong, C. K. & Mandel, L. (1985) Measurement of time delays in the parametric production of photon pairs. Physical Review Letters 54, 20112013.
Fuwa, M., Takeda, S., Zwierz, M., Wiseman, H. & Furusawa, A. (2015). Experimental proof of nonlocal wavefunction collapse for a single particle using homodyne measurements. Nature Communication 6, 16. doi: 10.1038/ncomms 7665.
Gefter, A. (2014). Theoretical physics: complexity on the horizon. Nature 509, 552553.
Gisin, N. & Thew, R. (2007). Quantum communication. Nature Photonics 1, 165171.
Giustina, M., Versteegh, M. A., Wengerowsky, S., Handsteiner, J., Hochrainer, A., Phelan, K., Steinlechner, F., Kofler, J., Larsson, J.-Å., Abellan, C., Amaya, W., Pruneri, V., Mitchell, M. W., Bever, J., Gerrits, T., Lita, A. E., Shalm, L. K., Nam, S. W., Scheidl, T., Ursin, R., Wittman, B. & Zeilinger, A. (2015). Significant loophole-free test of Bell's theorem with entangled photons. Physical Review Letters 115, 250401250406.
Gosh, R. & Mandel, L. (1987). Observation of nonclassical effects in the interference of two photons. Physical Review Letters 59, 19031905.
Grangier, P., Roger, G. & Aspect, A. (1986). Experimental evidence for a photon anticorrelation effect on a beamsplitter: a new light on single-photon interferences. Europhysics Letters 1, 173179.
Griffiths, D. J. (2008). Introduction to Quantum Mechanics, 2nd edn, pp. 207210. New Jersey: Wiley-VCD.
Guerreiro, T., Sanguinetti, B., Zbinden, H., Gisin, N. & Suarez, A. (2012). Single-photon space-like antibunching. Physics Letters A 376, 21742177.
Halpin, A., Johnson, P. J. M., Tempelaar, R., Murphy, R. S., Knoester, J., Jansen, T. L. C. & Miller, R. J. D. (2014). Two-dimensional spectroscopy of a molecular dimer unveils the effects of vibronic coupling on exciton coherences. Nature Chemistry 6, 196201.
Hensen, B., Bernien, H., Dreau, A. E., Reiserer, A., Kalb, N., Blok, M. S., Ruitenberg, J., Vermeulen, R. F. L., Shouten, R. N., Abellán, C., Maya, M., Pruneri, V., Mitchell, M. W., Markham, M., Twitchen, D. J., Elkouss, D., Wehner, S., Taminiau, T. H. & Hanson, R. (2015). Loophole-free Bell inequality violation using electron spins separated by 1·3 kilometres. Nature 526, 682686.
Hong, C. K., Ou, Z. Y. & Mandel, L. (1987). Measurement of subpicosecond time intervals between two photons by interference. Physical Review Letters 59, 20442046.
Horne, M. A. & Zeilinger, A. (1985). A Bell type EPR experiment using linear momenta. In Proc. Symp. on Found. of Mod. Physics (eds. P. Lahiti & P. Mittelstaedt), p. 435. World Scientific, Singapore.
Jammer, M. (1974). The Philosophy of Quantum Mechanics, p. 115. Singapore: John Wiley.
Johnson, A. C., Petta, J. R., Taylor, J. M., Yacoby, A., Lukin, M. D., Marcus, C. M., Hanson, M. P. & Gossard, A. C. (2005) Triplet-singlet spin relaxation via nuclei in a double quantum dot. Nature 435, 925928.
Kasha, M. (1963). Energy transfer mechanisms and the molecular exciton model for molecular aggregates. Radiation Research 20, 5571.
Kemble, E. C. (1935). The correlation of wavefunctions with the state of physical systems. Physical Review 47, 973974.
Kim, Y.-H. (2003). Two-photon interference without bunching two photons. Physics Letters A 315, 352357.
Kimble, H. J., Dagenais, M. & Mandel, L. (1977). Photon Antibunching in Resonance Fluorescence. Physical Review Letters 39, 691695.
Kocher, C. A. & Commins, E. D. (1967). Polarization correlation of photons emitted in an atomic cascade. Physical Review Letters 18, 575579.
Kwiat, P. G., Steinberg, A. M. & Chiao, R. Y. (1993). High visibility interference in a Bell-inequality experiment for energy and time. Physical Reviews A 47, 2472–247.
Larsson, J.-Å. (1998). Detector efficiency in the Greenberger-Horne-Zeilinger paradox: independent errors. Physical Reviews A 57, 3303.
Leggett, A. J. (2002). Testing the limits of quantum mechanics: motivation, state of play, prospects. Journal of Physics: Condensed Matter 14, R415R451.
Leggett, A. J. (2003). Nonlocal hidden-variable theories and quantum mechanics: an incompatibility theorem. Foundations of Physics 33, 14691493.
Mair, A., Vaziri, A., Weihs, G. & Zeilinger, A. (2001). Entanglement of the orbital angular momentum states of photons. Nature 412, 313316.
Maldacena, J. & Susskind, L. (2013). Cool horizons for entangled black holes. Progress of Physics 61, 781811.
Ninham, B. W. & Daicic, J. (1998). Lifshitz theory of Casimir forces at finite temperature. Physical Reviews A 57, 18701877.
Nordén, B (1978). Applications of Linear Dichroism spectroscopy. Applied Spectroscopy Reviews 14, 157248; Appendix C.
Nordén, B., Elvingson, C., Jonsson, M. & Åkerman, B. (1991). Microscopic behaviour of DNA during electrophoresis: electrophoretic orientation. Quarterly Reviews of Biophysics 24, 103164.
Nordén, B., Rodger, A. & Dafforn, (2010). Linear Dichroism and Circular Dichroism. A Textbook on Polarized-light Spectroscopy, pp. 240250. Lomdon: The Royal Society of Chemistry.
Ou, Z. Y. & Mandel, L. (1988a). Violation of Bell's inequality and classical probability in a two-photon correlation experiment. Physical Review Letters 61, 5053.
Ou, Z. Y. & Mandel, L. (1988b). Observation of spatial quantum beating with separated photodetectors. Physical Review Letters 61, 5457.
Ou, Z. Y., Pereira, S. F., Kimble, H. J. & Peng, K. C. (1992a). Realization of the Einstein-Podolsky-Rosen paradox for continuous variables. Physical Review Letters 68, 36633666.
Ou, Z. Y., Pereira, S. F. & Kimble, H. J. (1992b). Realization of the Einstein-Podolsky-Rosen paradox for continuous variables in non-degenerate parametric amplification. Applied Physics B 55, 265278.
Panas, I. (2015). A tale of two entangled instabilities – dual role of delta oxygen in HgBa2Can-1CunO2(n+1)+δ . Entropy 17, 67656782.
Rose, T. S., Rosker, M. J. & Zewail, A. H. (1988). Femtosecond real time observation of wave packet oscillations (resonance) in dissociation reactions. Journal of Chemical Physics 88, 66726673.
Rowe, M. A., Kielpinski, D., Meyer, V., Sackett, C. A., Itano, W. M., Monroe, C. & Wineland, D. J. (2001). Experimental violation of a Bell's inequality with efficient detection. Nature 409, 791794.
Salart, D., Baas, A., Branciard, C., Gisin, N. & Zbinden, H. (2008 ). Testing the speed of ‘spooky action at a distance’. Nature 454, 861864.
Schrödinger, E. (1935). Discussion of probability relations between separated systems. Proceedings of the Cambridge Philosophical Society 31, 555563.
Shih, Y. H. & Alley, C. O. (1988). New type of Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by optical parametric down conversion. Physical Review Letters 61, 29212924.
Simon, R. (2000). Peres-horodecki separability criterion for continuous variable systems. Physical Review Letters 84, 27262729.
Stokes, G. G. (1852). Optical parameters for polarized light. Transactions of the Cambridge Philosophical Society 9, 399415.
Takeda, S., Mizuta, T., Fuwa, M., Yoshikawa, J.-I., Yonesawa, H. & Furusawa, (2013). A generation and eight-port homodyne characterization of time-bin qubits for continuous-variable quantum information processing. Physical Reviews A 87, 043803/1-5.
Turchette, Q. A., Wood, C. S., King, B. E., Myatt, C. J., Leibfried, D., Itano, W. M., Monroe, & Wineland, D. J. (1998). Deterministic entanglement of two trapped ions. Physical Review Letters 81, 36313634.
Van Enk, S. J., Luthenhaus, N. & Kimble, H. J. (2007). Experimental procedures for entanglement verification. Physical Review A 75, 115.
Van Ramsdonk, M. (2010). Building up spacetime with quantum entanglement. General Relativity and Gravitation 42, 23232329.
Van Vleck, J. H. (1932). Electric and Magnetic Susceptibilities, p. 318. Oxford: Clarendon Press.
Vaterlaus, A., Beutler, T. & Mair, F. (1991). Spin-lattice relaxation time of ferromagnetic gadolinium determined with time-resolved spin-polarization photo-emission. Physical Review Letters 67, 33143317.
Weihs, G., Jennewein, T., Simon, C., Weinfurter, H. & Zeilinger, A. (1998). Violation of Bell's inequality under strict Einstein locality conditions. Physical Review Letters 81, 50395046.
Wennerstrom, H., Daicic, J. & Ninham, B. W. (1999). Temperature dependence of atom-atom interactions. Physical Review A 60, 25812584.
Wennerström, H. & Westlund, P.-O. (2013). On Stern-Gerlach coincidence measurements and their application to Bell's theorem. Physics Essays 26, 174180.
White, R. M. (2007). Quantum Theory of Magnetisms: Magnetic Properties of Materials. Berlin: Springer-Verlag, Section 2.2.7.
Wratchtrup, J., von Borczyskowski, C., Bernard, J., Orrit, M. & Brown, R. (1993). Optically detected spin coherence of single molecules. Physical Review 71, 35653568.
Wu, C. S. & Shaknov, I. (1950). The angular correlation of scattered annihilation radiation. Physical Review 77, 136.
Yin, J., Cao, Y., Yong, H.-L., Ren, J.-G., Linag, H., Liao, S.-K., Zhou, F., Liu, C., Wu, Y.-P., Pan, G.-S., Zhang, Q., Peng, C.-Z. & Pan, J.-W. (2013). Bounding the speed of ‘spooky action at a distance’. Physical Review Letters 110, 260407260418.
Zager, S. A. & Freed, J. H. (1982). Electron spin relaxation and molecular dynamics in liquids: density dependence. Journal of Chemical Physics 77, 33603375.
Zbinden, H., Brendel, J., Gisin, N. & Tittel, W. (2001) Experimental test of nonlocal quantum correlation in rekativistic configurations. Physical Review A 63, 022111-1-10.
Zewail, A. H. (1988). Laser femtochemistry. Science 242, 16451653.
Zewail, A. H. (1990). The birth of molecules. Scientific American 263, 7686.

Related content

Powered by UNSILO

Quantum entanglement: facts and fiction – how wrong was Einstein after all?

  • Bengt Nordén (a1)


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.