Tripartite Entanglement Signal from Multipartite Entanglement of Purification

Abstract: We propose a signal $\Delta^{(3)}_p$ for genuine tripartite entanglement in finite-dimensional quantum systems and $\Delta^{(3)}_w$ for holographic systems. We prove that $\Delta^{(3)}_p$ is non-negative for any tripartite entangled mixed states. Based on the conjecture, the equality between an entanglement wedge cross section $E_w$ and entanglement of purification $E_p$, i.e., $E_w = E_P$ in the semiclassical limit, we apply the tripartite entanglement measure to study the structures of tripartite entanglement in AdS$_3$/CFT$_2$, especially for pure AdS$_3$. We comment on a generalization to $n$-partite entanglement signals $\Delta^{(n)}_p(A_1:\cdots:A_n)$.