Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Realization and characterization of a 2-photon 4-qubit linear cluster
  state
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat