Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Observation of twin beam correlations and quadrature entanglement by
  frequency doubling in a two-port resonator
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
18
The categories of this paper are: econ
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th