Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photon-exchange effects on photon-pair transmission   It has been proposed that photon-exchange effects in atom-photon interactions
could lead to greatly enhanced optical nonlinearities. These might have
widespread application (e.g. quantum information). Here we demonstrate
experimentally that such exchange effects can indeed enhance the probability of
real absorption of photon pairs. Using nonclassical pairs of photons with
variable time separation, we observe a maximum suppression of pair transmission
by at least 5% with respect to the result for uncorrelated photons.

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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
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The categories of this paper are: astro-ph
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom