Tripartite entanglement in the HaPPY code is not holographic

Abstract

Holographic states satisfy several entropic inequalities owing to the Ryu-Takayangi formula. A drawback of these inequalities is that they only use bipartite entanglement in their formulation. We investigate a recently proposed "GHZ-forbidding" inequality, built out of the reflected entropy and the tripartite multi-entropy, that holds for holographic states. We show that the inequality is either violated or saturated, but never strictly satisfied, by stabilizer states, thereby showing that stabilizer states are not holographic. As a consequence, we show that tripartite entanglement in the HaPPY code is not holographic.