Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Protection of entanglement between two two-level atoms   The dynamical evolution of entanglement between two polarizable two-level
atoms in weak interaction with electromagnetic vacuum fluctuations is
investigated. We find that, for initial Bell state $\psi^{\pm}$, the decay rate
of entanglement between atoms is just the superradiant spontaneous emission
rate, which depends not only on the spontaneous emission rate of atom but also
on the modulation of the spontaneous emission rate due to the presence of
another atom. It is shown that, with the presence of a boundary, the
entanglement between transversely polarizable atoms can be protected for a very
long time. It is pointed out that when the two atoms in initial Bell state
$\psi^{-}$ are put close enough , the entanglement between them can also be
protected.

30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
2
The categories of this paper are: math
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol