Quantum state tomography, entanglement detection and Bell violation prospects in weak decays of massive particles

Journal article

A rather general method for determining the spin density matrix of a multi-particle system from angular decay data is presented. The method is based on a Bloch parameterisation of the d-dimensional generalised Gell-Mann representation of ρ and exploits the associated Wigner- and Weyl-transforms on the sphere. Each parameter of a (possibly multipartite) spin density matrix can be measured from a simple average over an appropriate set of experimental angular decay distributions. The general procedures for both projective and non-projective decays are described, and the Wigner P and Q symbols calculated for the cases of spin-half, spin-one, and spin-3/2 systems. The methods are used to examine Monte Carlo simulations of pp collisions for bipartite systems: pp → W⁺W⁻, pp → ZZ, pp → ZW⁺, pp → W⁺t¯, tt¯, and those from the Higgs boson decays H → WW* and H → ZZ*. Measurements are proposed for entanglement detection, exchange symmetry detection and Bell inequality violation in bipartite systems.

Authors: Ashby-Pickering, R; Barr, AJ; Wierzchucka, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer
• Journal: Journal of High Energy Physics
• Volume: 2023
• Issue: 5
• Article number: 20
• Publication date: 2023-05-02
• Acceptance date: 2023-04-19
• DOI: 10.1007/JHEP05(2023)020
• EISSN: 1029-8479
• ISSN: 1126-6708
• Language: English
• Keywords: Higgs properties; quantum groups; FFR; electroweak precision physics