Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultraslow propagation of matched pulses by four-wave mixing in an atomic
  vapor   We have observed the ultraslow propagation of matched pulses in nondegenerate
four-wave mixing in a hot atomic vapor. Probe pulses as short as 70 ns can be
delayed by a tunable time of up to 40 ns with little broadening or distortion.
During the propagation, a probe pulse is amplified and generates a conjugate
pulse which is faster and separates from the probe pulse before getting locked
to it at a fixed delay. The precise timing of this process allows us to
determine the key coefficients of the susceptibility tensor. The presence of
gain in this system makes this system very interesting in the context of
all-optical information processing.

34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph