2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/137570We investigate how equilibrium entanglement is manifested in the nonlinear response of an $N$-qubit system. We show that in the thermodynamic limit the irreducible part of the $n$th-order nonlinear susceptibility indicates that the eigenstates of the system contain entangled $(n+1)$-qubit clusters. This opens the way to a directly observable multiqubit entanglement signature. We show that the irreducible part of the static cubic susceptibility of a system of four flux qubits, as a function of external parameters, behaves as a global 4-qubit entanglement measure introduced in Ref.\cite{Love}. We discuss the possibility of extracting purely-entanglement-generated contribution from the general multipoint correlators in a multiqubit system.Expanded version; new co-authors; numerical calculations and new figures added; to appear in Quantum Information Processing (2007)Quantum PhysicsOther Condensed Mattertext