Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Simple quantum feedback of a solid-state qubit   We propose an experiment on quantum feedback control of a solid-state qubit,
which is almost within the reach of the present-day technology. Similar to the
earlier proposal, the feedback loop is used to maintain the coherent (Rabi)
oscillations in a qubit for an arbitrary long time; however, this is done in a
significantly simpler way, which requires much smaller bandwidth of the control
circuitry. The main idea is to use the quadrature components of the noisy
detector current to monitor approximately the phase of qubit oscillations.
  The price for simplicity is a less-than-ideal operation: the fidelity is
limited by about 95%. The feedback loop operation can be experimentally
verified by appearance of a positive in-phase component of the detector current
relative to an external oscillating signal used for synchronization.

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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
32
The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol