Momentum entanglement at colliders: the $H \to WW,ZZ$ case

TL;DR

This work develops a discretised momentum-space framework to study quantum entanglement in collider processes, focusing on $H \to WW, ZZ$ decays. It constructs a spin–momentum density operator using the Jacob–Wick helicity formalism and aggregates momentum degrees of freedom into finite bins, enabling entanglement tests via the Peres–Horodecki criterion and related measures. The analysis demonstrates genuine momentum–momentum and spin–momentum entanglement in Higgs decays within the SM, with tripartite entanglement among momentum and the two boson spins, and provides quantified expectations for experimental observability. For $H \to ZZ \to 4\ell$, the paper presents realistic LHC and HL-LHC sensitivity forecasts, showing potential >$5\sigma$ evidence of these quantum correlations under CP conservation, highlighting a broadly applicable method for exploring momentum entanglement at the energy frontier.

Abstract

We address momentum entanglement in Higgs decays to weak boson pairs, $H \to WW,ZZ$, by discretising momentum space. The momenta of the two weak bosons are entangled, as well as the degrees of freedom in momentum and spin spaces. For $H \to ZZ$ in the four-lepton final state, we also estimate the statistical sensitivity of entanglement measures at the Large Hadron Collider and future upgrades. The discretisation method introduced here is broadly applicable, offering a framework for studies of momentum entanglement at the energy frontier.

Figures (1)

• Figure 1: Probability density functions for momentum entanglement measures, as obtained from the pseudo-experiments. The solid lines represent the best-fit Gaussian or skew-normal distributions.