Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory of Spectrum in Qubit-Oscillator Systems in the Ultrastrong
  Coupling Regime   Recent measurement on an LC resonator magnetically coupled to a
superconducting qubit[arXiv:1005.1559] shows that the system operates in the
ultra-strong coupling regime and crosses the limit of validity for the
rotating-wave approximation of the Jaynes-Cummings model. By using extended
bosonic coherent states, we solve the Jaynes-Cummings model exactly without the
rotating-wave approximation. Our numerically exact results for the spectrum of
the flux qubit coupled to the LC resonator are fully consistent with the
experimental observations. The smallest Bloch-Siegert shift obtained is
consistent with that observed in this experiment. In addition, the
Bloch-Siegert shifts in arbitrary level transitions and for arbitrary coupling
constants are predicted.

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The categories of this paper are: gr-qc
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The categories of this paper are: cs
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The categories of this paper are: adap-org
16
The categories of this paper are: stat
3
The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an