Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ion-Photon Entanglement and Bell Inequality Violation with 138Ba+   We report on the demonstration of ion-photon entanglement and Bell inequality
violation in a system of trapped 138Ba+ ions. Entanglement between the Zeeman
sublevels of the ground state of a single 138Ba+ ion and the polarization state
of a single 493 nm photon emitted by the ion with a fidelity of $0.84\pm0.01$
was achieved, along with a Bell signal of 2.3, exceeding the classical limit of
2 by over eight standard deviations. This system is a promising candidate for a
loophole-free Bell inequality violation test as the wavelengths of the
transitions of 138Ba+ are in the visible region and thus suitable for long
range transmission over fiber optic cable.

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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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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: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ph
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: cond-mat
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The categories of this paper are: eess