Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Retrieval of multiple spin waves from a weakly excited, metastable
  atomic ensemble   The emission of light from a multiply excited atomic ensemble is examined and
it is shown how symmetric (spin-wave) and non-symmetric states of excitation
radiate into spatially separate field modes. This observation has potential
application to single photon generation and spin wave entanglement, since in
the presence of atomic interactions it can result in isolated single photon
emission into a phase-matched field mode.

24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin