Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-Photon Polarization Interference for Pulsed SPDC in a PPKTP
  Waveguide   We study the spectral properties of Spontaneous Parametric Down Conversion in
a periodically poled waveguided structure of KTP crystal pumped by ultra-short
pulses. Our theoretical analysis reveals a strongly multimode and asymmetric
structure of the two-photon spectral amplitude for type-II SPDC. Experimental
evidence, based on Hong-Ou-Mandel polarization interference with narrowband
filtering, confirms this result.

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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: physics
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The categories of this paper are: hep-ph
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The categories of this paper are: math