Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cavity QED nondemolition measurement scheme using quantized atomic
  motion   Considering ultracold atoms traversing a high-Q Fabry-Perot cavity, we
theoretically demonstrate a quantum nondemolition measurement of the photon
number. This fully quantum mechanical approach may be understood utilizing
concepts as effective mass and group velocity of the atom. The various photon
numbers induce a splitting of the atomic wave packet, and a time-of-flight
measurement of the atom thereby reveals the photon number. While repeated
atomic measurements increase the efficiency of the protocol, it is shown that
by considering long interaction times only a few atoms are needed to resolve
the photon number with almost perfect accuracy.

25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin