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Relativistic causality limits nonlocal quantum correlations via uncertainty
Avishy Carmi [1] , Eliahu Cohen [2]
[1] Center for Quantum Information Science and Technology and Faculty of Engineering Sciences Ben-Gurion University of the Negev, Beersheba 8410501, Israel
[2] H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK
The seminal paper of Popescu and Rohrlich [S. Popescu, D. Rohrlich, Quantum nonlocality as an axiom, Found. Phys. 24, 379-385 (1994)] has led during the last two decades to extensive research focused on systematic study of nonlocality and axiomatic construction of quantum mechanics. However, their paper has also led to the belief that the plausible assumption of relativistic causality is not enough for bounding the strength of quantum correlations. Many basic principles have been suggested since then for finding the quantum bound on correlations, but none has fully succeeded in doing so from outside the Hilbert space structure. Moreover, during the last 23 years, it was believed that relativity theory allows correlations stronger-than-quantum to exist in Nature, implying that there is an unhealthy gap between quantum mechanics and special relativity.
In this work we propose a paradigm shift – the principle of relativistic causality is enough when considered within a general indeterministic framework (that is, when assuming the existence of uncertainty relations generalizing the quantum ones). Based solely on this non-quantum construction, we derive the state-of-the-art quantum bound for bipartite binary Bell scenarios, as well as another hitherto unnoticed quantitative characterization of quantum correlations. Furthermore, we outline a general scheme applicable to any multipartite scenario and any measured observables, which allows to find bounds on nonlocal quantum correlations.
If time allows, I will elaborate on the upcoming experimental demonstration in Ottawa with SPDC photons.
(The work is currently under review in Nat. Commun. and might be suitable also for the quantum foundations session)