English

Almost all pure entangled states enable unbounded nonlocality sharing

Quantum Physics 2026-07-27 v1

Abstract

We establish a connection between Hardy's paradox and nonlocality sharing in sequential bipartite scenarios, where each subsystem is measured in turn by a chain of observers. We show that any correlations exhibiting a Hardy paradox in the two-input two-output scenario enable sequential violations of the CHSH inequality between arbitrarily many pairs of observers, using only projective measurements and the assistance of a small local ancilla system. Since almost all pure entangled states, with the only exception of the maximally entangled one, admit Hardy correlations, our protocol applies generically: almost all pure entangled states, if assisted by a local ancilla, allow for nonlocality sharing between arbitrarily many observer pairs using only projective measurements.

Cite

@article{arxiv.2607.24700,
  title  = {Almost all pure entangled states enable unbounded nonlocality sharing},
  author = {Anna Steffinlongo and Nicola D'Alessandro and Martin J. Renner},
  journal= {arXiv preprint arXiv:2607.24700},
  year   = {2026}
}

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5+6 pages