Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-setting multi-site Bell inequalities for loophole-free tests with up
  to 50% loss   We consider Bell experiments with N spatially separated qubits where loss is
present and restrict to two measurement settings per site. We note the
Mermin-Ardehali-Belinskii-Klyshko (MABK) Bell inequalities do not present a
tight bound for the predictions of local hidden variable (LHV) theories. The
Holder-type Bell inequality derived by Cavalcanti, Foster, Reid and Drummond
provides a tighter bound, for high losses. We analyse the actual tight bound
for the MABK inequalities, given the measure W=\prod_{k=1}^{N}\eta_{k} of
overall detection efficiency, where \eta_{k} is the efficiency at the site k .
Using these inequalities, we confirm that the maximally entangled
Greenberger-Horne-Zeilinger state enables loophole-free falsification of LHV
theories provided \prod_{k=1}^{N}\eta_{k}>2^{(2-N)}, which implies a symmetric
threshold efficiency of \eta\rightarrow50%, as N\rightarrow\infty .
Furthermore, loophole-free violations remain possible, even when the efficiency
at some sites is reduced well below 0.5, provided N>3 .

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The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
3
The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: q-alg
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int