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Physical Review A

Quantum contextuality of spin-1 massive particles

Marco E. Fabbrichesi, Roberto Floreanini B, Emidio Gabrielli A, Luca Marzola

Published Jul 29, 2025• 4 citations
Publisher

Abstract

The authors take a close look at how spin\leavevmode\hbox{-}1 particles, like W bosons and certain mesons, behave in high-energy collisions and find clear signs of quantum contextuality in their polarizations. Using real collider data, they show that these uniquely quantum effects can be seen in practical experimental setups.
DOI
10.1103/9bvc-2w4m

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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.
Contextuality is a fundamental property of quantum mechanics. Contrary to entanglement, which can only exist in composite systems, contextuality is also present for single entities. The case of a three-level system is of particular interest because--in agreement with the Bell-Kochen-Specker theorem--it is the simplest in which quantum contextuality is necessarily present. We verify that the polarizations of spin-1 massive particles produced at collider experiments indeed exhibit contextuality. To this purpose we consider WWW gauge bosons produced in top-quark decays, J/ψJ/ψJ/ψ and K∗(892)0K^{*}(892)^0K∗(892)0 mesons created in BBB-meson decays and ϕϕϕ mesons resulting from χc0χ^0_cχc0​ charmonium decays, making use of the data collected and analyzed by the ATLAS, LHCb and BESIII collaborations, respectively. The polarizations of all these four particles show contextuality with a significance of more than 5σ5σ5σ.
Recent research on quantum contextuality has been strongly centered on device-independent frameworks, such as the many graph approaches to contextuality and the celebrated sheaf-theoretical approach. Contextuality is described in these frameworks as a property of data only, making it possible to characterize and quantify the phenomena regardless of the reasons why it occurs. In this paper we look beyond the data and focus on possible explanations for this experimental fact. We show that a classical system generating contextual data can easily be found if the following conditions are satisfied (1) We only have access to a specific collection of epistemic measurements (which, all things considered, is basically Bohr's view on quantum measurements) and (2) There is a limitation on which of these measurements can be jointly performed. The way we see it, this example indicates that contextuality may be a consequence of the type of measurement taken into account, instead of an intrinsic feature of the system upon which these measurements are performed; if this is correct, the widespread idea that quantum contextuality is a non-classical feature can be avoided.
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The study of confinement in quantum spin chains has seen a large surge of interest in recent years.It is not only important for understanding a range of effective one-dimensional condensed-matter realizations but it also shares some of the nonperturbative physics with quantum chromodynamics (QCD), which makes it a prime target for current quantum simulation efforts.In analogy to QCD, the confinementinduced two-particle bound states that appear in these models are dubbed mesons.Here, we study scattering events due to meson collisions in a quantum spin chain with long-range interactions such that two mesons have an extended interaction.We show how novel hadronic bound states, e.g., with four constituent particles akin to tetraquarks, may form dynamically in fusion events.In a natural collision their signal is weak, as elastic meson scattering dominates.However, we propose two controllable protocols that allow for a clear observation of dynamical hadron formation.We discuss how this physics can be simulated in trapped-ion or Rydberg-atom setups.