Size-Independent Robustness in Multipartite Bell Self-Testing

Abstract:Practical robust self-testing of multipartite entanglement has so far been restricted to small-scale systems due to error bounds that degrade severely with system size. In this work, we establish multipartite self-testing with robustness independent of the size of the quantum network. We derive a fully analytic, device-independent self-testing bound for $n$-qubit Greenberger-Horne-Zeilinger (GHZ) states. The bound scales linearly with the observed violation error and lies universally within a constant factor of two from a theoretical upper bound. Furthermore, the operator-inequality framework reduces the verification of the conjectured optimal bound to a highly efficient numerical check, which we perform up to $n=100$. Consequently, GHZ entanglement can be certified under a fixed noise level in arbitrarily large systems, enabling scalable device-independent verification.

arXiv:2608.30851 [quant-ph]

(or arXiv:2608.30851v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2608.30851 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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