Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optimal quantum estimation of loss in bosonic channels   We address the estimation of the loss parameter of a bosonic channel probed
by Gaussian signals. We derive the ultimate quantum bound on precision and show
that no improvement may be obtained by having access to the environment degrees
of freedom. We found that, for small losses, the variance of the optimal
estimator is proportional to the loss parameter itself, a result that
represents a qualitative improvement over the shot noise limit. An observable
based on the symmetric logarithmic derivative is derived, which attains the
ultimate bound and may be implemented using Gaussian operations and photon
counting.

18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an