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Configuration of separability and tests for multipartite entanglement in Bell-type experiments

Koji Nagata·Masato Koashi·Nobuyuki Imoto
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Abstract

We derive tight quadratic inequalities for all kinds of hybrid separable-inseparable $n$-particle density operators on an arbitrary dimensional space. This methodology enables us to truly derive a tight quadratic inequality as tests for full $n$-partite entanglement in various Bell-type correlation experiments on the systems that may not be identified as a collection of qubits, e.g., those involving photons measured by incomplete detectors. It is also proved that when the two measured observables are assumed to precisely anti-commute, a stronger quadratic inequality can be used as a witness of full $n$-partite entanglement.

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Koji Nagata, Masato Koashi, Nobuyuki Imoto. 2002-11-20. Configuration of separability and tests for multipartite entanglement in Bell-type experiments. https://doi.org/10.1103/physrevlett.89.260401

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