Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Linear optical implementation of a single mode quantum filter and
  generation of multi-photon polarization entangled state   We propose a scheme to implement a single-mode quantum filter, which
selectively eliminates the one-photon state in a quantum state
$\alpha|0>+\beta|1>+\gamma|2>$. The vacuum state and the two photon state are
transmitted without any change. This scheme requires single-photon sources,
linear optical elements and photon detectors. Furthermore we demonstrate, how
this filter can be used to realize a two-qubit projective measurement and to
generate multi-photon polarization entangled states.

34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
3
The categories of this paper are: physics
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc