Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-photon scattering of a tightly focused weak light beam from a small
  atomic ensemble : an optical probe to detect atomic level structures   We study two-photon scattering of a tightly focused weak light beam from a
small atomic ensemble of two-level atoms (2LAs). This is similar to the
scattering of photons from an atomic ensemble in a one-dimensional waveguide.
The scaling of two-photon nonlinearity at single-photon resonance shows a
non-monotonic behaviour with an increasing number of few identical 2LAs. The
two-photon nonlinearity decays monotonically with an increasing number of atoms
for incident photons detuned from single-photon resonance. Single-photon
transport in two 2LAs is similar to that in a single V-type three-level atom
(3LA). However two-photon transport in these two systems shows very different
line-shapes. When single-photon transmission is zero in these systems, two
transmitted photons are bunched together in a V-type 3LA, while their
correlation is zero in two 2LAs. The difference in the two-photon line-shape
persists for few 2LAs and 3LAs. Therefore, the two-photon scattering of a
tightly focused weak light beam can be used as a probe to detect atomic level
structures of different atoms with similar transition energies.

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The categories of this paper are: alg-geom
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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The categories of this paper are: econ
10
The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: nlin