Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Experimental observation of double-peak structure of coincidence spectra
  in ultra-fast Spontaneous Parametric Down Conversion   The requirement on the symmetry of the biphoton wave function results in a
double peak structure of the coincidence spectra of Spontaneous Parametric Down
Conversion (SPDC) [1]. In this work we report the experimental observation of
this effect by careful tailoring parameters of the SPDC crystal, the ultra-fast
pump laser, and the measurement setup. The results are shown to be relevant to
quantum state engineering of ultra-fast polarization-, or frequency-entangled
mixed states.

23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
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The categories of this paper are: funct-an
9
The categories of this paper are: nlin
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
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The categories of this paper are: eess