Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Experimental transmission of quantum digital signatures over 90-km of
  installed optical fiber using a differential phase shift quantum key
  distribution system
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org