Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Experimental continuous-variable entanglement from a
  phase-difference-locked optical parametric oscillator   We observed continuous-variable entanglement between the bright beams emitted
above threshold by an ultrastable optical parametric oscillator, classically
phase-locked at a frequency difference of 161.8273240(5) MHz. The
amplitude-difference squeezing is -3 dB and the phase-sum one is -1.35 dB.
Besides proving entanglement in a new physical system, the phase-locked OPO,
such unprecedented frequency-difference stability paves the way for
transferring entanglement between different optical frequencies and densely
implementing continuous-variable quantum information in the frequency domain.

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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: cs
34
The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph