2026/08/05 by Weikang Li, Mengyao Hu, Dong-Ling Deng +1
Physics and Astronomy · #quant-ph
arxiv created 2026/08/05 · arxiv updated 2026/08/07
Bell experiments rule out local common-cause explanations of quantum correlations, yet they do not exclude hidden influences that travel faster than light while still having a finite speed in a preferred frame. Multipartite spacetime arrangements turn this possibility into a constraint: two late parties that are outside each other's hidden-influence cones must remain Bell-local once the earlier events are fixed. Here, we formulate this constraint as a projected-polytope separation problem for cluster-state correlations, using only marginal data containing at most one late party. From linear cluster states, we construct a four-qubit witness with the bound S4≤ 6 and quantum value 4+2√2, and a five-qubit witness with S5≤ 10 and quantum value 6+4√2. We certify that the exposed faces are facets of the corresponding projected hidden-influence polytopes. These results identify linear-cluster graph states as certifiable and experimentally friendly resources for finite-speed hidden-influence tests.