Maximally entangled gluons for any x

Individual quarks and gluons at small x inside an unpolarized hadron can be regarded as Bell states in which qubits in the spin and orbital angular momentum spaces are maximally entangled. Using the machinery of quantum information science, we generalize this observation to all values 0<x<1 and describe gluons (but not quarks) as maximally entangled states between a qubit and a qudit. We introduce the conditional probability distribution P(lz|sz) of a gluon’s orbital angular momentum lz given its helicity sz. Restricting to the three states lz=0,±1, which constitute a qutrit, we explicitly compute P as a function of x. Published by the American Physical Society 2025