Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superbunching and Nonclassicality as new Hallmarks of Superradiance   Superradiance, i.e., spontaneous emission of coherent radiation by an
ensemble of identical two-level atoms in collective states introduced by Dicke
in 1954, is one of the enigmatic problems of quantum optics. The startling gist
is that even though the atoms have no dipole moment they radiate with increased
intensity in particular directions. Following the advances in our understanding
of superradiant emission by atoms in entangled $W$ states we examine the
quantum statistical properties of superradiance. Such investigations require
the system to have at least two excitations as one needs to explore the
photon-photon correlations of the radiation emitted by such states. We present
specifically results for the spatially resolved photon-photon correlations of
systems prepared in doubly excited $W$ states and give conditions when the
atomic system emits nonclassial light. Equally, we derive the conditions for
the occurrence of bunching and even of superbunching, a rare phenomenon
otherwise known only from nonclassical states of light like the squeezed
vacuum. We finally investigate the photon-photon cross correlations of the
spontaneously scattered light and highlight the nonclassicalty of such
correlations.

24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph