Abstract
Harrigan and Spekkens (Found Phys 40:125–157, 2010), introduced the influential notion of an ontological model of operational quantum theory. Ontological models can be either “epistemic” or “ontic.” According to the two scholars, Einstein would have been one of the first to propose an epistemic interpretation of quantum mechanics. Pusey et al. (Nat Phys 8:475–478, 2012) showed that an epistemic interpretation of quantum theory is impossible, so implying that Einstein had been refuted. We discuss in detail Einstein’s arguments against the standard interpretation of QM, proving that there is a misunderstanding in Harrigan and Spekkens’ attribution of an epistemic perspective to Einstein, whose point of view was actually statistical, but in a quasi-classical sense.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Notes
But see footnote 15.
Note that the common opinion is that quantum mechanics violates S but not LC; see, for instance, the papers collected in Cushing and McMullin (1989).
Obviously, Einstein’s strong completeness presupposes EPR’s one, in the sense that if one or more elements of reality would not be represented in the theory, the bijective correspondence would not exist.
According to Howard (2015, pp. 128ff.), Einstein was progressively aware of the distinction between locality and separability. Here, we will not insist on this distinction.
It should be noted, however, that some scholars find controversial and dubious the foundational significance of PBR’s assumptions. For instance, Mansfield (2016) does not agree on the acceptability of “preparation independence” as a premise of PBR’s argument.
Perhaps PBR is a threat for QBism. Indeed, Fuchs and Schack (2015), in order to avoid problems for QBism deriving from PBR’s argument, deny that QBism is an ontological model in HS’ sense.
Just an example: We know that light is a wave phenomenon. However, the first models of its behavior were couched in the framework of geometrical optics. This theory is, thus, an epistemically incomplete theory insofar as it does not capture the undulatory aspects of light; it does not allow for reaching full knowledge of this physical phenomenon. Nevertheless, geometrical optics is not ontologically incomplete with respect to the wave character of light, since, intrinsically, it does not possess the theoretical ingredients able to describe electromagnetic waves. Both an epistemically incomplete theory and an ontologically incomplete one are not the best theories to capture a certain class of phenomena, but the former cannot even be the best theory as, being, as it were, at the maximum of its possibilities, it is not able to take into account some phenomena, so that it is condemned to remain incomplete. The latter actually could be the best theory, in the sense that, not having fully exploited its potentialities, it could be made complete, at least in principle.
It is also HS’ completeness.
Note that if separability does not hold, it would not be possible to introduce separated wave functions as ψ1 and ψ2.
Lehner (2014, pp. 331ff.) interprets Einstein’s argument in the same way. Nonetheless, he emphasizes that the jump from the many terms of the theory for one reality to one term for many realities does not hold. But Einstein (both in dialectica and in Schilpp’s volume) begins his argument assuming only two possible positions: the standard one and the incompleteness one. The former presupposes a 1-1 relation between theory and reality. Therefore, after showing that this does not hold (provided the acceptance of separability and locality), one is compelled to endorse the other attitude. Moreover, the many wave functions connected to different measurements represent different aspects of the physical reality of system B, so that the generic ψAB preceding the measurement is statistically incomplete.
The standard answer to Einstein’s argument would be that it is sufficient to give up separability—a possibility Einstein never accepted—to avoid the multiple wave functions; and the violation of separability is not incompatible with relativity.
That is, these particles follow Maxwell–Boltzmann statistics.
Note that, using HS’ language, a statistical interpretation states that p2(k/l1,M)p2(k/l2,M) ≠ 0, with l1 and l2 ∈ Λ and l1 ≠ l2. It is not obvious that this implies p1(λ|Pψ)p1(λ|Pφ) ≠ 0. In other terms, even if the same measurement, given different situations, could produce the same outcome, this does not entail (prima face) that two different preparations produce the same ontic situation.
References
Albert D, Ney A (eds) (2013) The wave function. Oxford University Press, Oxford
Bacciagaluppi G, Crull E (2018) The Einstein paradox: the debate on nonlocality and incompleteness in 1935. Cambridge University Press, Cambridge
Ballentine LE (1998) Quantum mechanics. A modern development. World Scientific, Singapore
Brown H (2016) The reality of the quantum state. New arguments and old, lecture at XII ontology international congress, Donostia
Cushing JT, McMullin E (eds) (1989) Philosophical consequences of quantum theory: reflections on Bell’s theorem. University of Notre Dame Press, Notre Dame
Einstein A (1934) On the method of theoretical physics. Philos Sci 1(2):163–169
Einstein A (1948) Quanten-Mechanik und Wirklichkeit. dialectica 2: 320–324. Translated in English in: Born M, Einstein A (1971) The Born-Einstein letters. Correspondence between Albert Einstein and Max and Hedwig Born from 1916 to 1955. Macmillan, London, pp 168–173
Einstein A (1949) Autobiographical notes. In: Schilpp PA (ed) Albert Einstein. Philosopher-scientist. MJF Books, New York, pp 1–95
Einstein A, Podolski B, Rosen N (1935) Can quantum mechanical description of physical reality be considered complete? Phys Rev 47:777–780
Fuchs CA (2010) QBism, the perimeter of quantum Bayesianism. https://arxiv.org/abs/1003.5209
Fuchs CA, Schack R (2015) QBism and the Greek: why a quantum state does not represent an element of physical reality. https://arxiv.org/abs/1412.4211
Harrigan N, Spekkens RW (2010) Einstein, incompleteness, and the epistemic view of quantum states. Found Phys 40:125–157
Home D, Whittaker A (2007) Einstein’s struggle with quantum theory. Springer, New York
Howard D (2015) Anche Einstein gioca a dadi. Carocci, Roma
Jammer M (1974) The philosophy of quantum mechanics: the interpretation of quantum mechanics in historical perspective. Wiley, New York
Lange M (2002) An introduction to the philosophy of physics. Wiley, Malden
Lehner C (2014) Einstein’s realism and his critique of quantum mechanics. In: Janssen M, Lehner C (eds) The Cambridge companion to Einstein. Cambridge University Press, Cambridge, pp 306–353
Mansfield S (2016) Reality of the quantum state: towards a stronger ψ-ontology theorem. Phys Rev A 94(4):042124. https://doi.org/10.1103/PhysRevA.94.042124
Pusey MF, Barrett J, Rudolph T (2012) On the reality of the quantum state. Nat Phys 8:475–478
Schlosshauer M (2007) Decoherence and the quantum-classical transition. Springer, Berlin
Acknowledgements
We thank Claudio Calosi, who discussed with us the topic of the paper.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Fano, V., Macchia, G. & Tarozzi, G. Is Einstein’s Interpretation of Quantum Mechanics Ψ-Epistemic?. Axiomathes 29, 607–619 (2019). https://doi.org/10.1007/s10516-018-9382-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10516-018-9382-6