Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: EPR Beams and Photon Number Detector: Toward Synthesizing Optical
  Nonlinearity
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex