Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum nondemolition measurement of a light field component by a
  feedback compensated beam splitter   In conventional quantum nondemolition measurements, the interaction between
signal and probe preserves the measured variable. Alternatively, it is possible
to restore the original value of the variable by feedback. In this paper, we
describe a quantum nondemolition measurement of a quadrature component of the
light field using a feedback compensated beam splitter. The noise induced by
the vacuum port of the beam splitter is compensated by a linear feedback
resulting in an effective amplification of the observed variable. This
amplification is then be reversed by optical parametric amplification to
restore the original value of the field component.

31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
18
The categories of this paper are: econ