Qubit-qubit-qutrit quantum correlations in H → f f̅ V
Abstract
We perform an extensive analysis of the quantum correlations carried by the qubit-qubit-qutrit pure state arising in the decay of a massive scalar into a fermion-antifermion pair and a massive gauge boson, H → f f̅ V, specialising to the Higgs boson decay h → τ- τ+ Z. Working with the exact tree-level spin state and its systematic expansion around the massless-fermion limit, we obtain analytic control over the entire phase space: the bipartite entanglement measures, the genuine 2 ⊗ 2 ⊗ 3 entanglement structure (the Miyake classification), as well as the Bell-inequality violations and the non-stabiliserness (magic) are all mapped and reproduced by compact formulas. The bipartite measures exhibit a monogamy-like trade-off between the fermion pair and the fermion-boson pairs. The state is genuinely 2 ⊗ 2 ⊗ 3 entangled over almost the entire phase space, most strongly in the collinear regions. We derive, for the first time, semi-analytical expressions for the tight 4 × 4 × 2 Bell inequalities of the 2 ⊗ 2 ⊗ 3 system, generalising the optimisation previously available only for three qubits, and find that the local-hidden-variable bound is violated over the entire phase space, reaching within a few per cent of the quantum bound at the upper endpoint of the di-tau mass spectrum. We further extend the stabiliser Rényi entropy and the non-local magic to systems with unequal local dimensions, and show that the near-endpoint state carries almost exactly one bit of non-local magic, which peaks at log2 27/7 ≃ 1.95 in the collinear regions. The differential decay rate concentrates precisely in the most nonclassical region of the phase space.
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BibTeX
@misc{banacki2026qubitqubitqutrit,
title = {{Qubit-qubit-qutrit quantum correlations in $H \to f \bar f V$}},
author = {Michał Banacki and Misaki Ohta and Abhyoudai S. Shaleena and Paweł Caban and Michał Eckstein and Kazuki Sakurai and Michael Spannowsky and Paweł Horodecki},
howpublished = {arXiv},
year = {2026},
month = jul,
doi = {10.48550/arxiv.2607.26122},
eprint = {2607.26122},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.26122},
}
RIS
TY - UNPB
TI - Qubit-qubit-qutrit quantum correlations in H → f f̅ V
AU - Michał Banacki
AU - Misaki Ohta
AU - Abhyoudai S. Shaleena
AU - Paweł Caban
AU - Michał Eckstein
AU - Kazuki Sakurai
AU - Michael Spannowsky
AU - Paweł Horodecki
PY - 2026
DA - 2026/07/28
PB - arXiv
DO - 10.48550/arxiv.2607.26122
UR - https://arxiv.org/abs/2607.26122
AB - We perform an extensive analysis of the quantum correlations carried by the qubit-qubit-qutrit pure state arising in the decay of a massive scalar into a fermion-antifermion pair and a massive gauge boson, H → f f̅ V, specialising to the Higgs boson decay h → τ^- τ^+ Z. Working with the exact tree-level spin state and its systematic expansion around the massless-fermion limit, we obtain analytic control over the entire phase space: the bipartite entanglement measures, the genuine 2 ⊗ 2 ⊗ 3 entanglement structure (the Miyake classification), as well as the Bell-inequality violations and the non-stabiliserness (magic) are all mapped and reproduced by compact formulas. The bipartite measures exhibit a monogamy-like trade-off between the fermion pair and the fermion-boson pairs. The state is genuinely 2 ⊗ 2 ⊗ 3 entangled over almost the entire phase space, most strongly in the collinear regions. We derive, for the first time, semi-analytical expressions for the tight 4 × 4 × 2 Bell inequalities of the 2 ⊗ 2 ⊗ 3 system, generalising the optimisation previously available only for three qubits, and find that the local-hidden-variable bound is violated over the entire phase space, reaching within a few per cent of the quantum bound at the upper endpoint of the di-tau mass spectrum. We further extend the stabiliser Rényi entropy and the non-local magic to systems with unequal local dimensions, and show that the near-endpoint state carries almost exactly one bit of non-local magic, which peaks at log_2 27/7 ≃ 1.95 in the collinear regions. The differential decay rate concentrates precisely in the most nonclassical region of the phase space.
ER -