  We investigate the radiative processes of a quantum system composed by two
identical two-level atoms in the de Sitter spacetime, interacting with a
conformally coupled massless scalar field prepared in the de Sitter-invariant
vacuum. We discuss the structure of the rate of variations of the atomic energy
for two static atoms. Following a procedure developed by Dalibard, Dupont-Roc
and Cohen-Tannoudji, our intention is to identify in a quantitative way the
contributions of vacuum fluctuations and the radiation reaction to the
generation of quantum entanglement and to the degradation of entangled states.
We find that when the distance between two atoms larger than the characteristic
length scale, the rate of variation of atomic energy in the de Sitter-invariant
vacuum behaves differently compared with that in the thermal Minkowski
spacetime. In particular, the generation and degradation of quantum
entanglement can be enhanced or inhibited, which are dependent not only on the
specific entangled state but also on the distance between the atoms.
