Communications in Mathematical Physics

, Volume 334, Issue 2, pp 533–628

A Combinatorial Approach to Nonlocality and Contextuality

  • Antonio Acín
  • Tobias Fritz
  • Anthony Leverrier
  • Ana Belén Sainz
Article

DOI: 10.1007/s00220-014-2260-1

Cite this article as:
Acín, A., Fritz, T., Leverrier, A. et al. Commun. Math. Phys. (2015) 334: 533. doi:10.1007/s00220-014-2260-1

Abstract

So far, most of the literature on (quantum) contextuality and the Kochen–Specker theorem seems either to concern particular examples of contextuality, or be considered as quantum logic. Here, we develop a general formalism for contextuality scenarios based on the combinatorics of hypergraphs, which significantly refines a similar recent approach by Cabello, Severini and Winter (CSW). In contrast to CSW, we explicitly include the normalization of probabilities, which gives us a much finer control over the various sets of probabilistic models like classical, quantum and generalized probabilistic. In particular, our framework specializes to (quantum) nonlocality in the case of Bell scenarios, which arise very naturally from a certain product of contextuality scenarios due to Foulis and Randall. In the spirit of CSW, we find close relationships to several graph invariants. The recently proposed Local Orthogonality principle turns out to be a special case of a general principle for contextuality scenarios related to the Shannon capacity of graphs. Our results imply that it is strictly dominated by a low level of the Navascués–Pironio–Acín hierarchy of semidefinite programs, which we also apply to contextuality scenarios.

We derive a wealth of results in our framework, many of these relating to quantum and supraquantum contextuality and nonlocality, and state numerous open problems. For example, we show that the set of quantum models on a contextuality scenario can in general not be characterized in terms of a graph invariant.

In terms of graph theory, our main result is this: there exist two graphs \({G_1}\) and \({G_2}\) with the properties
$$\begin{array}{ll}\qquad \qquad \alpha(G_1) \; = \; \Theta(G_1), \qquad \qquad \alpha(G_2) \,= \; \vartheta(G_2), \\ \Theta(G_1\boxtimes G_2) \, > \; \Theta(G_1) \cdot \Theta(G_2),\quad \Theta(G_1 + G_2) \, > \Theta(G_1) + \Theta(G_2).\end{array}$$

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Antonio Acín
    • 1
    • 2
  • Tobias Fritz
    • 3
  • Anthony Leverrier
    • 4
  • Ana Belén Sainz
    • 1
  1. 1.ICFO-Institut de Ciències FotòniquesCastelldefelsSpain
  2. 2.ICREA-Institució Catalana de Recerca i Estudis AvançatsBarcelonaSpain
  3. 3.Perimeter Institute for Theoretical PhysicsWaterlooCanada
  4. 4.INRIA Rocquencourt, Domaine de VoluceauLe Chesnay CedexFrance

Personalised recommendations