Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum cryptography using photon source based on postselection from
  entangled two-photon states   A photon source based on postselection from entangled photon pairs produced
by parametric frequency down-conversion is suggested. Its ability to provide
good approximations of single-photon states is examined. Application of this
source in quantum cryptography for quantum key distribution is discussed.
Advantages of the source compared to other currently used sources are
clarified. Future prospects of the photon source are outlined.

0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs