Gap between holographic and quantum mechanical extreme rays of the subadditivity cone

We show via explicit construction that for six or more parties, there exist extreme rays of the subadditivity cone that can be realized by quantum states, but not by holographic states. This is a counterexample to a conjecture first formulated in Hernández-Cuenca [The holographic entropy cone from marginal independence, .], and implies the existence of deep holographic constraints that restrict the allowed patterns of independence among various subsystems beyond the universal quantum mechanical restrictions.