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arXiv · 2604.03884

Formalizing CHSH Rigidity in Lean 4

Tianrun Zhao·Nengkun Yu
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Abstract

Violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality certifies genuine quantum correlations. In this work, we formalize in Lean 4 the rigidity theorem -- any strategy achieving near-optimal CHSH value must be locally isometric to the canonical qubit strategy. In the course of formalization, we identified a gap in the argument of McKague, Yang, and Scarani (arXiv:1203.2976).

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Tianrun Zhao, Nengkun Yu. 2026-04-04. Formalizing CHSH Rigidity in Lean 4. https://arxiv.org/abs/2604.03884

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