Abstract
In this paper we intend to discuss the importance of providing a physical representation of quantum superpositions which goes beyond the mere reference to mathematical structures and measurement outcomes. This proposal goes in the opposite direction to the project present in orthodox contemporary philosophy of physics which attempts to “bridge the gap” between the quantum formalism and common sense “classical reality”—precluding, right from the start, the possibility of interpreting quantum superpositions through non-classical notions. We will argue that in order to restate the problem of interpretation of quantum mechanics in truly ontological terms we require a radical revision of the problems and definitions addressed within the orthodox literature. On the one hand, we will discuss the need of providing a formal redefinition of superpositions which captures explicitly their contextual character. On the other hand, we will attempt to replace the focus on the measurement problem, which concentrates on the justification of measurement outcomes from “weird” superposed states, and introduce the superposition problem which focuses instead on the conceptual representation of superpositions themselves. In this respect, after presenting three necessary conditions for objective physical representation, we will provide arguments which show why the classical (actualist) representation of physics faces severe difficulties to solve the superposition problem. Finally, we will also argue that, if we are willing to abandon the (metaphysical) presupposition according to which ‘Actuality = Reality’, then there is plenty of room to construct a conceptual representation for quantum superpositions.
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Notes
See for example, in this same respect, the detailed analysis of the concept of space in the history of physics provided by Max Jammer in his excellent book: The Concepts of Space. The History of Theories of Space in Physics (Jammer 1993).
See de Ronde et al. (2014) for discussion and definition of this notion in the context of classical physics.
According to Bohr (Wheeler and Zurek 1983, p. 7): “[...] the unambiguous interpretation of any measurement must be essentially framed in terms of classical physical theories, and we may say that in this sense the language of Newton and Maxwell will remain the language of physicists for all time.” In this respect, he aso added [Op. cit., p. 7] that, “it would be a misconception to believe that the difficulties of the atomic theory may be evaded by eventually replacing the concepts of classical physics by new conceptual forms.”
I am grateful to Bob Coecke for this linguistic insight. Cagliari, July 2014.
Given a quantum system represented by a superposition of more than one term, \(\sum c_i | \alpha _i \rangle\), when in contact with an apparatus ready to measure, \(|R_0 \rangle\), QM predicts that system and apparatus will become “entangled” in such a way that the final ‘system + apparatus’ will be described by \(\sum c_i | \alpha _i \rangle |R_i \rangle\). Thus, as a consequence of the quantum evolution, the pointers have also become—like the original quantum system—a superposition of pointers \(\sum c_i |R_i \rangle\). This is why the measurement problem can be stated as a problem only in the case the original quantum state is described by a superposition of more than one term.
[Op. cit., p. 156].
The Born rule provides the probability of finding a certain observable via the numbers that accompany the kets within quantum superpositions.
There is in our neo-Spinozist account an implicit ontological pluralism of multiple representations which can be related to one reality through a univocity principle. This is understood in analogous manner to how Spinoza considers in his immanent metaphysics the multiple attributes as being expressions of the same one single substance, namely, nature (see de Ronde 2014, 2016). Our non-reductionistic answer to the problem of inter-theory relation escapes in this way the requirement present in almost all interpretations of QM which implicitly or explicitly attempt to explain the formalism in substantialist atomistic terms. We believe there might be an interesting connection between our neo-Spinozist approach and the ‘multiplex realism’ recently proposed by Aerts and Sassoli de Bianchi (2015). Due to the limited space of this paper we leave this particular analysis and comparison for a future work.
It is true that QBism does provide a subjectivist interpretation of probability following the Bayesian viewpoint, however, this is done so at the price of denying the very need of an interpretation for QM. See for a detailed analysis: de Ronde (2016), de Ronde (2016). Also the hidden measurement approach by Aerts provides an epistemic interpretation of quantum probability but in this case, instead of considering the quantum system alone, the approach focuses on the measurement interaction between system and apparatus (Aerts and Sassoli di Bianchi 2015, 2017).
For a more detailed discussion of the notion of immanent cause we refer to (Melamed 2013, Chapter 2).
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Acknowledgements
I wish to thank two anonymous reviewers for their careful reading of my manuscript and their many insightful comments and suggestions. This work was partially supported by the following grants: FWO project G.0405.08 and FWO-research community W0.030.06. CONICET RES. 4541-12 and the Project PIO-CONICET-UNAJ (15520150100008CO) “Quantum Superpositions in Quantum Information Processing”.
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Fellow Researcher of the Consejo Nacional de Investigaciones Científicas y Técnicas and Adjoint Professor of the National University Arturo Jaurteche, Buenos Aires, Argentina.
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de Ronde, C. Quantum Superpositions and the Representation of Physical Reality Beyond Measurement Outcomes and Mathematical Structures. Found Sci 23, 621–648 (2018). https://doi.org/10.1007/s10699-017-9541-z
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DOI: https://doi.org/10.1007/s10699-017-9541-z