Automated computation of spin-density matrices and quantum observables for collider physics
(2026) Journal of High Energy Physics — Vol. 04 (2026)
Files
document.pdf
Open Access - Adobe PDF
- 5.96 MB
Details
- Authors
- Abstract
- We present a fully automated framework to compute production spin-density matrices for generic collider processes at tree level within MadGraph5_aMC@NLO. The method assembles helicity amplitudes into event-by-event production matrices. These are written to the LHE file in a compact form, together with run metadata, enabling direct post-processing of quantum observables. The implementation supports bi- and multipartite qubit and qutrit final states, configurable reference frames, and both polarised and unpolarised initial states. A companion, easy-to-extend library provides analysis routines to determine key quantum-information measures and witnesses. These include purity, concurrence, and entanglement of formation for qubits; Peres-Horodecki tests and negativity; spin-polarisation vectors and correlation matrices; D-coefficients; and stabiliser-based “magic” measures. As a result, multi-particle quantum correlations can be quantified systematically. We validate the implementation against known results for $ t\overline{t} $ and VV (V = W$^{±}$, Z) production in pp and e$^{+}$e$^{−}$ collisions and in heavy-resonance decays. We then consider new applications and study quantum correlations in several LHC final states: $ t\overline{t}{W}^{\pm } $, tW$^{−}$ vs. $ t\left(\overline{t}\to {W}^{-}\overline{b}\right) $, and $ t\overline{t}t $ vs. $ t\overline{t}t\overline{t} $.
- Affiliations
Citations
Durupt, V., Maltoni, F., & Mattelaer, O. (2026). Automated computation of spin-density matrices and quantum observables for collider physics. Journal of High Energy Physics, 04. https://doi.org/10.1007/JHEP04(2026)103 (Original work published 2026)