A Witness of GHZ Entanglement Using Only Collective Spin Measurements

• URL: http://arxiv.org/abs/2311.00805v2
• Date: Mon, 1 Apr 2024 16:47:05 GMT
• Title: A Witness of GHZ Entanglement Using Only Collective Spin Measurements
• Authors: Lin Htoo Zaw, Khoi-Nguyen Huynh-Vu, Valerio Scarani,
• Abstract summary: We introduce an entanglement witness that detects GME of spin ensembles, whose total spin is half-integer, using only collective spin measurements. States detected by our witness are close to a family of GHZ-like states, which includes GHZ states of an odd number of spin-half particles.
• Score: 0.0
• License: http://creativecommons.org/licenses/by-sa/4.0/
• Abstract: Of existing entanglement witnesses that utilize only collective measurements of a spin ensemble, not all can detect genuine multipartite entanglement (GME), and none can detect Greenberger-Horne-Zeilinger (GHZ) states beyond the tripartite case. We fill this gap by introducing an entanglement witness that detects GME of spin ensembles, whose total spin is half-integer, using only collective spin measurements. Our witness is based on a nonclassicality test introduced by Tsirelson, and solely requires the measurement of total angular momentum along different directions. States detected by our witness are close to a family of GHZ-like states, which includes GHZ states of an odd number of spin-half particles. We also study the robustness of our witness under depolarizing noise, and derive exact noise bounds for detecting noisy GHZ states.

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