Analysis of Some Recent Tests of Quantum Contextuality

Jochen Szangolies

Dengke Qu, Kunkun Wang, Lei Xiao +2 more

Abstract Contextuality is a phenomenon at the heart of quantum mechanics different from classical behavior and has been recently identified as a resource in quantum information processing. Experimental demonstration of contextuality is thus an important goal. We experimentally demonstrate a test of state-independent contextuality in a four-dimensional Hilbert space with single photons and violate the inequality by at least 387 standard deviations. Despite imperfections and possible measurement disturbance, our results cannot be explained in non-contextual models. We also provide a theoretical analysis of a test of contextuality with a coherent light field and show how the definitions affect the emergence of non-classical correlations. Our result sheds new light on the conflict between quantum and classical physics.

Marco E. Fabbrichesi, Roberto Floreanini B, Emidio Gabrielli A +1 more

Quantum contextuality refers to the impossibility of assigning a predefined, intrinsic value to a physical property of a system independently of the context in which the property is measured. It is, perhaps, the most fundamental feature of quantum mechanics. The many states with different spin that particle physics provides are the ideal setting for testing contextuality. We verify that the polarization states of single spin-1 massive particles produced at colliders are contextual. We test W + gauge bosons produced in top-quark decays, J / ψ and K * ( 892 ) 0 mesons in B -meson decays and ϕ mesons in χ c 0 and χ c 1 charmonium decays by reinterpreting the data and the analyses of the ATLAS, LHCb, Belle II and BESIII experimental collaborations, respectively. The polarization states of these four particles show contextuality with a significance larger than 5 σ . We also discuss the presence of quantum contextuality in spin states of bipartite systems formed by spin- 1 / 2 particles. We test Λ and Σ baryons reinterpreting two BESIII data analyses, and pairs of top quarks utilizing a recent analysis of the CMS Collaboration. Quantum contextuality is present with a significance exceeding 5 σ also in these cases. In addition, we study the feasibility of testing quantum contextuality by means of Z boson production in association with the Higgs boson, Z and W bosons pairs created in Higgs boson decays and with pairs of τ leptons. For the latter, we use Monte Carlo simulations that mimic the settings of SuperKEKB and of future lepton colliders. Experiments at high energies, though not designed for the purpose, perform surprisingly well in testing for quantum contextuality.

Gerhard Kirchmair, F. Zähringer, R. Gerritsma +5 more

Brian R. La Cour, Luigi Accardi, Guillaume Adenier +5 more

The question of quantum contextuality in the Mermin‐Peres square is considered. It is shown that a deterministic, noncontextual hidden variable model of this problem is not inconsistent with quantum mechanics, contrary to the Kochen‐Specker theorem. The key idea is that measurement outcomes may be viewed as deterministic functions of hidden variable states which are disturbed through the process of measurement. This, in turn, implies that the outcome of measuring the product of two commensurate observables need not be equal to the product of the outcomes that would have been obtained had they been measured individually. A critical analysis of some recent and proposed experimental tests of contextuality is also provided.

J. Acácio de Barros, Ehtibar N. Dzhafarov, Janne V. Kujala +1 more