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  • Open Access

L Entropy: A New Genuine Multipartite Entanglement Measure

Jaydeep Kumar Basak1,*, Vinay Malvimat2,†, and Junggi Yoon2,3,4,‡

  • *Contact author: jkb.hep@gmail.com
  • †Contact author: vinaymalvimat@khu.ac.kr
  • ‡Contact author: junggi.yoon@khu.ac.kr
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Phys. Rev. Lett. 136, 080202 – Published 24 February, 2026

DOI: https://doi.org/10.1103/kmpl-mdbx

Abstract

We advance “latent entropy” (L entropy) as a novel measure to characterize genuine multipartite entanglement in pure states, applicable to quantum systems with both finite and infinite degrees of freedom. This measure, derived from an upper bound on reflected entropy, attains its maximum for three-party Greenberger-Horne-Zeilinger states and n=4, 5-party 2-uniform states. We establish that it satisfies all essential properties of a genuine multipartite entanglement measure, including being a pure-state entanglement monotone. We further obtain an analog of the Page curve by analyzing the behavior of L entropy in multiboundary wormholes, emphasizing their connection to multipartite entanglement in random states. Specifically, for n=5, we show that random states approximate 2-uniform states, exhibiting maximal multipartite entanglement. Extending these ideas to finite temperatures, we introduce the multipartite thermal pure quantum state, a generalization of the thermal pure quantum state to multipartite systems, and demonstrate that the entanglement structure in states of the multicopy Sachdev-Ye-Kitaev model exhibits finite-temperature 2-uniform behavior.

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Phys. Rev. Lett. 136, 080202– Published 24 February, 2026
  • Received 1 June 2025
  • Accepted 30 January 2026
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