Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single-photon quantum nondemolition detectors constructed with linear
  optics and projective measurements   Optical quantum nondemolition devices can provide essential tools for quantum
information processing. Here, we describe several optical interferometers that
signal the presence of a single photon in a particular input state without
destroying it. We discuss both entanglement-assisted and
non-entanglement-assisted interferometers, with ideal and realistic detectors.
We found that existing detectors with 88% quantum efficiency and single-photon
resolution can yield output fidelities of up to 89%, depending on the input
state. Furthermore, we construct expanded protocols to perform QND detections
of single photons that leave the polarization invariant. For detectors with 88%
efficiency we found polarization-preserving output fidelities of up to 98.5%.

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The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
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The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
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The categories of this paper are: nlin
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga