Bounds on nonlocal correlations in the presence of signaling and their application to topological zero modes

Avishy Carmi, Yaroslav Herasymenko, Eliahu Cohen, Kyrylo Snizhko

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Bell's theorem renders quantum correlations distinct from those of any local-realistic model. Although being stronger than classical correlations, quantum correlations are limited by the Tsirelson bound. This bound, however, applies for Hermitian, commutative operators corresponding to non-signaling observables in Alice's and Bob's spacelike-separated labs. As an attempt to explore theories beyond quantum mechanics and analyze the uniqueness of the latter, we examine in this work the extent of non-local correlations when relaxing these fundamental assumptions, which allows for theories with non-local signaling. We prove that, somewhat surprisingly, the Tsirelson bound in the Bell-Clauser-Horne-Shimony-Holt scenario, and similarly other related bounds on non-local correlations, remain effective as long as we maintain the Hilbert space structure of the theory. Furthermore, in the case of Hermitian observables we find novel relations between non-locality, local correlations, and signaling. We demonstrate that such non-local signaling theories are naturally simulated by quantum systems of parafermionic zero modes. We numerically study the derived bounds in parafermionic systems, confirming the bounds' validity yet finding a drastic difference between correlations of 'signaling' and 'non-signaling' sets of observables. We also propose an experimental procedure for measuring the relevant correlations.

Original languageEnglish
Article number073032
JournalNew Journal of Physics
Issue number7
StatePublished - 18 Jul 2019


  • Bell CHSHinequalities
  • Tsirelson bound
  • parafermions
  • quantum correlations
  • signaling
  • weak measurements

ASJC Scopus subject areas

  • General Physics and Astronomy


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