Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Inducing electron spin coherence in GaAs quantum well waveguides: Spin
  coherence without spin precession   Electron spin coherence is induced via light-hole transitions in a quantum
well waveguide without either an external or internal DC magnetic field. In the
absence of spin precession, the induced spin coherence is detected through
effects of quantum interference in the spectral domain coherent nonlinear
optical response. We interpret the experimental results qualitatively using a
simple few-level model with only the optical transition selection rule as its
basic ingredients.

1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph