Any Physical Theory of Nature Must Be Boundlessly Multipartite Nonlocal

IQC Math/CS Seminar - Marc-Olivier Renou (INRIA, Paris-Saclay)

Quantum correlations are obtained when multiple parties perform independent measurements on a shared quantum state.  Bell’s seminal theorem proves that certain correlations predicted by quantum theory resist explanations in terms of any Local Hidden Variable theory based on shared randomness. But what about alternative explanations for quantum correlations, in terms of a hypothetical causal theory involving exotic bipartite resources generalising quantum bipartite entanglement in addition to shared randomness? 

With Xavier Coiteux-Roy and Elie Wolfe, we found that no such exotic causal theory can account for all quantum correlations, thus generalizing Bell's theorem. In this talk, I will show that there exists a concrete Bell-like experiment which achieves correlations impossible to simulate with exotic bipartite resources and unbounded shared randomness. This certifies the fact that No Bipartite-Nonlocal Causal Theory Can Explain Nature's Quantum Correlations. I will generalise this result to any N-Partite-Nonlocal Causal Theory, and discuss three experimental realisations of the proposed protocol.

Our proof is based on the inflation technique in which we assume the replicability of resources, showing that a concept commonly used in distributed computing is also of great interest in theoretical physics.

On a more practical aspect, we introduce a redefinition of the notion of genuine multipartite nonlocality which can be used in practice to justify the multipartite nonclassicality of a concrete experimental system.

Based on arXiv:2105.09381, arXiv:2105.09380, arXiv:2201.12754

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