Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Narrowband Biphoton Generation due to Long-Lived Coherent Population
  Oscillations   We study the generation of paired photons due to the effect of four-wave
mixing in an ensemble of pumped two-level systems that decay via an
intermediate metastable state. The slow population relaxation of the metastable
state to the ground state is utilized to create long-lived coherent population
oscillation, leading to narrowband nonlinear response of the medium. The
biphotons have a narrow bandwidth, long coherence time and length, which can be
controlled by the pump field. In addition, the biphotons are antibunched, with
antibunching period determined by the dephasing time. During this period,
damped oscillations of the biphoton wavefunction occurs if the pump detuning is
non-zero.

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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: astro-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: eess