Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Singular Perturbation Approximations for a Class of Linear Quantum
  Systems   This paper considers the use of singular perturbation approximations for a
class of linear quantum systems arising in the area of linear quantum optics.
The paper presents results on the physical realizability properties of the
approximate system arising from singular perturbation model reduction.

12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio