Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum limits and symphotonic states in free-mass gravitational-wave
  antennae   Quantum mechanics sets severe limits on the sensitivity and required
circulating energy in traditional free-mass gravitational-wave antennas. One
possible way to avoid these restrictions is the use of intracavity QND
measurements. We analyze a new QND observable, which possesses a number of
features that make it a promising candidate for such measurements and propose a
practical scheme for the realization of this measurement. In combination with
an advanced coordinate meter, this scheme makes it possible to lower
substantially the requirements on the circulating power.

6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph