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arXiv · 2605.19117

Quantum Magic Reveals CP Phases Invisible to Entanglement in Spin-0 Decays

Nicolas Viaux·Ariel Norambuena·Pedro Orellana
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Abstract

All standard scalar quantum-information measures -- concurrence, negativity, entanglement entropy, the optimized CHSH bound, and quantum Fisher information -- are CP-blind in ideal \\ spin-0 $\to f\bar f$ decays because the two-qubit spin state is maximally entangled for every CP angle. We show that stabilizer magic, fixed in the physical Pauli frame of spin analysis, escapes this blind spot: the stabilizer R\'enyi entropy admits an exact closed form, vanishing at CP-definite and Clifford phases and peaking at maximal non-Clifford mixing. Two experimentally accessible, magic-inspired CP witnesses follow; the linear amplitude is $14.3\times$ more efficient than its quartic counterpart and reaches discovery-level sensitivity at the HL-LHC for $H\to\tau^+\tau^-$.

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Nicolas Viaux, Ariel Norambuena, Pedro Orellana. 2026-05-18. Quantum Magic Reveals CP Phases Invisible to Entanglement in Spin-0 Decays. https://arxiv.org/abs/2605.19117

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