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arXiv · 1405.2021

Universal methods for extending any entanglement witness from the bipartite to the multipartite case

Bang-Hai Wang·Hai-Ru Xu·Simone Severini
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Abstract

Any bipartite entanglement witness $W$ can be written as $W=c_σI-σ$, where $σ$ is a quantum state, $I$ is the identity matrix, and $c_σ$ is a non-negative number. We present a general method to extend the given entanglement witness to multipartite cases via purification, partial purification, and direct tensor of the quantum state $σ$. Our methods extend $σ$ but leave the parameter $c_σ$ untouched. This is very valuable since the parameter is generally not easy to compute.

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Bang-Hai Wang, Hai-Ru Xu, Simone Severini. 2014-08-17. Universal methods for extending any entanglement witness from the bipartite to the multipartite case. https://doi.org/10.1103/physreva.90.022312

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