English

Tripartite Haar random state has no bipartite entanglement

Quantum Physics 2026-05-21 v3 High Energy Physics - Theory

Abstract

We show that no EPR-like bipartite entanglement can be distilled from a tripartite Haar random state ΨABC|\Psi\rangle_{ABC} by local unitaries or local operations when each subsystem AA, BB, or CC has fewer than half of the total qubits. Specifically, we derive an upper bound on the probability of sampling a state with EPR-like entanglement at a given EPR fidelity tolerance, showing a doubly-exponential suppression in the number of qubits. Our proof relies on a simple volume argument supplemented by an ϵ\epsilon-net argument and concentration of measure. Viewing ΨABC|\Psi\rangle_{ABC} as a bipartite quantum error-correcting code CABC\to AB, this implies that neither output subsystem AA nor BB supports any non-trivial logical operator. We also establish general constraints on the structure of tripartite entanglement in Haar random states, showing that W- or GHZ-like entanglement cannot be distilled and that nontrivial global symmetries are absent. Finally, we discuss a physical interpretation in the AdS/CFT correspondence, indicating that a connected entanglement wedge does not necessarily imply bipartite entanglement, contrary to a previous belief.

Keywords

Cite

@article{arxiv.2502.04437,
  title  = {Tripartite Haar random state has no bipartite entanglement},
  author = {Zhi Li and Takato Mori and Beni Yoshida},
  journal= {arXiv preprint arXiv:2502.04437},
  year   = {2026}
}

Comments

(v1) 14 pages, 5 figures; (v2) an author (Zhi Li) added. Improved bounds with new results on local operation distillation and logical operators; (v3) Added Sections 1.2.4 and 5 discussing generalizations, Section 1.4 for intuitions of the proofs, a comment in relation to QFT entanglement in Section 6.1, and an additional comment in Section 7. 36 pages, 5 figures

R2 v1 2026-06-28T21:35:23.527Z