Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constructing optimal entanglement witnesses. II   We provide a class of optimal nondecomposable entanglement witnesses for 4N x
4N composite quantum systems or, equivalently, a new construction of
nondecomposable positive maps in the algebra of 4N x 4N complex matrices. This
construction provides natural generalization of the Robertson map. It is shown
that their structural physical approximations give rise to entanglement
breaking channels.

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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: nlin
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an