Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Entanglement of Gaussian states and the applicability to quantum key
  distribution over fading channels   Entanglement properties of Gaussian states of light as well as the security
of continuous variable quantum key distribution with Gaussian states in
free-space fading channels are studied. These qualities are shown to be
sensitive to the statistical properties of the transmittance distribution in
the cases when entanglement is strong or when channel excess noise is present.
Fading, i.e. transmission fluctuations, caused by beam wandering due to
atmospheric turbulence, is a frequent challenge in free-space communication. We
introduce a method of fading discrimination and subsequent post-selection of
the corresponding sub-states and show that it can improve the entanglement
resource and restore the security of the key distribution over a realistic
fading link. Furthermore, the optimal post-selection strategy in combination
with an optimized entangled resource is shown to drastically increase the
protocol robustness to excess noise, which is confirmed for experimentally
measured fading channel characteristics. The stability of the result against
finite data ensemble size and imperfect channel estimation is also addressed.

9
The categories of this paper are: nlin
2
The categories of this paper are: math
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio