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Il ruolo del teorema di Kochen-Specker nelle formulazioni con variabili nascoste della meccanica quantistica. On the role of Kochen-Specker theorem in hidden variable formulations of quantum mechanics

Elia De Sabbata

Published Sep 1, 2018• 0 citations
OpenAlex

Abstract

In this work we begin with a critical review of the concept of observable in a generical physical theory; relying on C*-algebras formalism and on Gelfand-Naimark theorem we justify the link between observables and operators in an Hilbert space. We discuss particularly observables of quantum mechanics, introducing some mathematical results that characterizes them. We introduce the problem of hidden variables and the hypothesis of non-contextuality, than we give a proof of the Kochen-Specker theorem in dimension greater or equal to 3 using partial algebras formalism; we also show a constructive example of an hidden variable theory in dimension 2. Finally we discuss Meyer’s and Kent’s objections relying on finite precision of physical measurements and we present colorations of S² ∩ Q³ and of dense subsets of the projectors of C^n and l²(C) that respect Kochen-Specker rules.

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Alastair A. Abbott, Cristian S. Calude, Jonathan Conder +1 more

The Kochen-Specker theorem shows the impossibility for a hidden variable theory to consistently assign values to certain (finite) sets of observables in a way that is noncontextual and consistent with quantum mechanics. If we require noncontextuality, the consequence is that many observables must not have pre-existing definite values. However, the Kochen-Specker theorem does not allow one to determine which observables must be value indefinite. In this paper we present an improvement on the Kochen-Specker theorem which allows one to actually locate observables which are provably value indefinite. Various technical and subtle aspects relating to this formal proof and its connection to quantum mechanics are discussed. This result is then utilized for the proposal and certification of a dichotomic quantum random number generator operating in a three-dimensional Hilbert space.

arXiv:1207.2029•Physical Review A•Dec 17, 2012•87 citations
In this work we begin with a critical review of the concept of observable in a generical physical theory; relying on C*-algebras formalism and on Gelfand-Naimark theorem we
justify the link between observables and operators in an Hilbert space. We discuss particularly observables of quantum mechanics, introducing some mathematical results that characterizes them. We introduce the problem of hidden variables and the hypothesis of non-contextuality, than we give a proof of the Kochen-Specker theorem in dimension greater or equal to 3 using partial algebras formalism; we also show a constructive example of an hidden variable theory in dimension 2. Finally we discuss Meyer’s and Kent’s objections relying on finite precision of physical measurements and we present colorations of S² ∩ Q³ and of dense subsets of the projectors of C^n and l²(C) that respect Kochen-Specker rules.
This paper examines no-hidden-variables theorems in quantum mechanics from the point of view of statistical mechanics. It presents a general analysis of the measurement process in the Boltzmannian framework that leads to a characterization of (in)compatible measurements and reproduces several features of quantum probabilities often described as “non-classical”. The analysis is applied to versions of the Kochen–Specker and Bell theorems to shed more light on their implications. It is shown how, once the measurement device and the active role of the measurement process are taken into account, contextuality appears as a natural feature of random variables. This corroborates Bell’s criticism that no-go results of the Kochen–Specker type are based on gratuitous assumptions. In contrast, Bell-type theorems are much more profound, but should be understood as nonlocality theorems rather than no-hidden-variables theorems. Finally, the paper addresses misunderstandings and misleading terminology that have confused the debate about hidden variables in quantum mechanics.
Abstract In chapter 12 we give an overview of the historical development of hidden-variable theories aiming to attribute ‘hidden’ definite outcomes to any potential measurement on a quantum system. We start with a discussion of von Neumann’s assumption on hidden-variable models, which was later realized not to hold by Hermann, Kochen, Specker, and Bell, going into detail on Bell’s refutation of von Neumann’s arguments. We then turn to the notion of contextuality, which severely restricts hidden-variable models: we discuss Gleason’s theorem before stating and proving the famous Kochen-Specker theorem, as well as the simpler versions of Peres’ nonet and Mermin’s pentagram. These results show that quantum mechanics is not compatible with the assignment of definite measurement outcomes to all possible measurements, and such assignments can hence only be made once a restricted set of observables, a context, is selected
The Kochen–Specker theorem shows that it is impossible to assign sharp values to all dynamical variables in quantum mechanics in such a way that the algebraic relations among the values of dynamical variables whose self-adjoint operators commute are the same as those among the operators themselves. We point out that, for quantum theories obtained by quantizing some classical theory, this condition – Kochen–Specker non-contextuality – is implausible from the start because quantization usually changes algebraic relations. We explain why this is so, using the formalism of deformation quantization and its conception of star products , and we illustrate the relevance of this point using various examples of dynamical variables quantized via Weyl quantization and coherent state quantization. Our observations suggest that the relevance of the Kochen–Specker theorem to the question of whether one can assign sharp values to all dynamical variables is rather limited.
This thesis explores the exact differences between the two most well-known no-hidden variable theories: the Bell theorem and the Kochen-Specker theorem. Furthermore, it tries to place a newer result called `the free will theorem', as developed by John Conway and Simon Kochen, in this context. To compare the Bell and Kochen-Specker theorems a reformulation of the two theorems by David Mermin will be discussed, which turns out to lead to an even stronger no-hidden variable theory. From the discussion of the free will theorem and the critical reactions it has elicited, it will become clear that the free will theorem is actually very similar to this stronger no-hidden variable theory.
The Kochen-Specker theorem shows the impossibility for a hidden variable theory to consistently assign values to certain (finite) sets of observables in a way that is noncontextual and consistent with quantum mechanics. If we require noncontextuality, the consequence is that many observables must not have pre-existing definite values. However, the Kochen-Specker theorem does not allow one to determine which observables must be value indefinite. In this paper we present an improvement on the Kochen-Specker theorem which allows one to actually locate observables which are provably value indefinite. Various technical and subtle aspects relating to this formal proof and its connection to quantum mechanics are discussed. This result is then utilized for the proposal and certification of a dichotomic quantum random number generator operating in a three-dimensional Hilbert space.