Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multitudes of Stable States in a Periodically Driven Electron-Nuclear
  Spin System in a Quantum Dot   The periodical modulation of circularly polarized light with a frequency
close to the electron spin resonance frequency induces a sharp change of the
single electron spin orientation. Hyperfine interaction provides a feedback,
thus fixing the precession frequency of the electron spin in the external and
the Overhauser field near the modulation frequency. The nuclear polarization is
bidirectional and the electron-nuclear spin system (ENSS) possesses a few
stable states. A similar frequency-locking effect exists for two-color and
mode-locked excitations, too. However, the pulsed excitation with mode locked
laser brings about the multitudes of stable states in ENSS in a quantum dot.
The resulting precession frequencies of the electron spin differ in these
states by the multiple of the modulation frequency. Under such conditions ENSS
represents a digital frequency converter with more than a hundred stable
channels.

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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas