Spin entanglement signatures of proton from a light-front Hamiltonian

TL;DR

This paper compares proton spin entanglement from two models, revealing that the quark-diquark model predicts higher entanglement than the BLFQ approach, highlighting differences in internal hadron structure.

Contribution

It introduces a comparative analysis of proton spin entanglement using BLFQ and quark-diquark models, emphasizing the differences in their entanglement structures.

Findings

Quark-diquark model shows higher spin entanglement than BLFQ.

Differences mainly due to W-type and Bell-type entanglement.

Stronger coupling and smaller quark mass in BLFQ favor quark-diquark configurations.

Abstract

Quantum entanglement provides a quantitative probe of the internal structure of hadrons and offers a sensitive means to study the quantum correlation in the hadron wave functions. For baryons, the spin state of the three valence quarks forms a tripartite qubit system, whose entanglement structure can be characterized by the four classes of three-qubit states. In this work, we compare the proton spin entanglement obtained from Basis Light-Front Quantization (BLFQ) with that from a quark-diquark model. By analyzing both bipartite and tripartite entanglement, we find that the quark-diquark model yields a substantially more entangled spin state than the BLFQ wave function in the valence Fock sector. This difference mainly originates from the larger W-type and Bell-type entanglement in the quark-diquark model. Within BLFQ, larger stronger coupling constant and smaller quark mass drive the spin correlation among the valence quarks towards an effective quark-diquark configuration with an active $d$ quark and a correlated $uu$ pair.