Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Implementation of continuous variable quantum cryptography in optical
  fibres using a go-&-return configuration   We demonstrate an implementation of quantum key distribution with continuous
variables based on a go-&-return configuration over distances up to 14km. This
configuration leads to self-compensation of polarisation and phase
fluctuations. We observe a high degree of stability of our set-up over many
hours.

22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex