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Article
Physics, Multidisciplinary
Yoav Afik et al.
Summary: Top quarks are a promising system for studying quantum information at high-energy scales. Current research focuses on entanglement, Bell nonlocality, and quantum tomography. This study provides a comprehensive understanding of quantum correlations in top quarks, including quantum discord and steering. Both phenomena are found to exist at the LHC, with quantum discord in separable quantum states expected to be detected with high statistical significance. These measurements are highly demanding but could provide evidence of CP-violating physics beyond the standard model, unlike entanglement.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Particles & Fields
Rachel Ashby-Pickering et al.
Summary: This article presents a method for determining the spin density matrix of a multiparticle system from angular decay data. The method uses a Bloch parameterisation of the d-dimensional generalised Gell-Mann representation of rho and utilizes the Wigner and Weyl transforms on the sphere. Each parameter of the (possibly multipartite) spin density matrix can be measured through averaging experimental angular decay distributions. The article describes the general procedures for projective and non-projective decays, and calculates the Wigner P and Q symbols for spin-half, spin-one, and spin-3/2 systems. The methods are applied to Monte Carlo simulations of bipartite systems in pp collisions, including pp -> W+W-, pp -> ZZ, pp -> ZW(+), pp -> W+ (t) over bar, t (t) over bar, as well as Higgs boson decays H -> WW* and H -> ZZ*. Measurements are proposed for entanglement detection, exchange symmetry detection, and Bell inequality violation in bipartite systems.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Astronomy & Astrophysics
Philipe De Fabritiis et al.
Summary: A relativistic Quantum Field Theory framework is used to study Mermin's inequalities. By introducing unitary operators using smeared Dirac spinor fields, GHZ-type states can be created from the Minkowski vacuum |0). The study reveals a relation between the expectation value of Mermin's operators in the vacuum and in the GHZ-type states, and shows that Mermin's inequalities are maximally violated when evaluated on these states.
Article
Astronomy & Astrophysics
S. P. Sorella
Summary: We discuss the relationship between Bogoliubov transformations, squeezed states, entanglement, and the maximum violation of the Bell-CHSH inequality. We point out a simple and general method to construct the bounded operators involved in the Bell-CHSH inequality, which is applicable to a wide range of models from quantum mechanics to relativistic quantum field theories. Various examples are provided to illustrate this framework, including entangled spin-one particles, squeezed oscillators, and the vacuum state in Minkowski spacetime parametrized by the Unruh temperature.
Article
Astronomy & Astrophysics
G. Peruzzo et al.
Summary: By employing a free scalar quantum field theory model introduced previously, the authors attempt to formulate the Bell-CHSH inequality within the Feynman path integral. They observe that the Bell-CHSH inequality naturally extends to quantum field theory and is compatible with the time ordering T. By treating the Feynman propagator as a distribution and introducing a suitable set of test functions, they work out the path integral setup for the Bell-CHSH inequality, obtaining the same results as canonical quantization.
Article
Astronomy & Astrophysics
David Dudal et al.
Summary: In this paper, we propose a general setup to investigate the violation of the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality in the vacuum state in the context of quantum field theory. By constructing specific test functions and satisfying relativistic causality requirements, we report violations of the Bell-CHSH inequality as close as desired to Tsirelson's bound.
Article
Astronomy & Astrophysics
Alan J. Barr
Summary: The decay of Higgs boson can produce pairs of W bosons in a maximally entangled state, whose spin may violate Bell inequalities. Experimental reconstruction of the spin density matrix of the W-+/- pair shows near-maximal violation of the CGLMP inequality. Bell tests can be performed at various colliders, and statistically significant violations may be observable with controlled reconstruction effects and backgrounds.
Article
Quantum Science & Technology
Yoav Afik et al.
Summary: The paper presents the general framework of the quantum state of a top-antitop quark pair produced through quantum chromodynamics in a high-energy collider. It discusses the presence of entanglement and CHSH violation in different regions of phase space and provides experimental observables for these signatures. The validity of the quantum tomography protocol for top-antitop pair is extended to more general quantum states and any production mechanism.
Article
Astronomy & Astrophysics
G. Peruzzo et al.
Summary: This study investigates the Clauser-Horne-Shimony-Holt (CHSH) inequality within a relativistic quantum field theory model. A set of bounded Hermitian operators is introduced using Weyl operators, and a CHSH-type correlator is constructed and evaluated. Although the violation of the CHSH inequality is small compared to Tsirelson's bound in quantum mechanics, the model can be used to study Bell's inequalities in more physical cases such as the Higgs models.
Article
Physics, Particles & Fields
Claudio Severi et al.
Summary: This study presents the prospects of detecting quantum entanglement and the violation of Bell inequalities in (t)(t) events at the LHC. Using simulated events and unfolding techniques, the research finds that entanglement can be established accurately, but testing Bell inequalities is more challenging.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Multidisciplinary
M. Fabbrichesi et al.
Summary: Correlations between spin of top-quark pairs at a collider can be used to probe quantum entanglement at unexplored energies. A single observable can test the violation of Bell inequality with different confidence levels, taking into account detector effects. This test relies solely on spin correlations and does not require probabilistic determinations.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Yoav Afik et al.
Summary: This research proposes the detection of entanglement between the spins of top-antitop-quark pairs at the LHC, representing the first proposal of entanglement detection in a pair of quarks, and also the entanglement observation at the highest energy scale so far. The study shows that entanglement can be observed by direct measurement of the angular separation between the leptons arising from the decay of the top-antitop pair, and develops a simple protocol for the quantum tomography of the top-antitop pair.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Physics, Multidisciplinary
Edward Witten
REVIEWS OF MODERN PHYSICS
(2018)
Review
Physics, Mathematical
R Verch et al.
REVIEWS IN MATHEMATICAL PHYSICS
(2005)
Article
Optics
JÅ Larsson
