It is shown in the Markovian approximation that the relaxation of two atoms noninteracting with each other in the field of a common thermostat results in the entanglement of atomic states. With time, this entanglement either vanishes or takes a stationary value depending on the initial conditions.
It is shown that, in the Markov approximation, relaxation of two noninteracting atoms in the field of a common thermostat leads not only to decoherence but also to the opposite process of the entanglement of atomic states, which can take on a stationary value depending on the initial conditions. This region of initial conditions narrows as the mean number of photons in the thermostat increases. The main radiative mechanism destroying an arbitrary initial entanglement of atoms is interaction of each atom with its own thermostat independent of the other. All Markov relaxation models under consideration are based on the Lindblad equations.
Relying on the Peres-Horodecki criterion, we investigated the dynamics of appearance of the stationary entanglement in the system of two two-level atoms decaying in the field of common thermostat. We took into account their dipole-dipole interaction and the difference between their atomic frequencies. It was established, that in the absence of the dipole-dipole interaction the presence of the stationary entanglement has a strong dependence on the identity of atomic frequencies. The difference between them (due to their different locations in the crystal or thermal movement), leads to a disappearance of the stationary entanglement. Also we found the dependence of existence of the stationary entanglement from a correlation between the constant of the dipole-dipole interaction, the resonance wave shift and the constant of interaction with the thermostat field - it comes into existence only when the latter value becomes greater than the former ones.
We study the disentanglement dynamics of two giant atoms coupled to a common one-dimensional waveguide. We focus on the non-Markovian retarded effect in the disentanglement of the two giant atoms by taking the photon transmission time into account. By solving the time-delayed equations of motion for the probability amplitudes, we obtain the evolution of the entanglement of the two giant atoms, which are initially in the maximally entangled states in the single-excitation space. It is found that the retardation-induced non-Markovianity leads to nonexponential decay and revivals of entanglement. Concretely, we consider separate-, braided-, and nested-coupling configurations, and find that the disentanglement dynamics in these configurations exhibits different features. We demonstrate that the steady-state entanglement depends on the time delay under certain conditions in these three coupling configurations. We also study the dependence of the disentanglement of the two giant atoms on both the detuning effect and the initial-state phase effect. In addition, we consider the disentanglement dynamics of the two giant atoms, which are initially in the state superposed by zero-excitation and two-excitation components. This work will pave the way for the generation of stationary entanglement between two giant atoms, which may have potential applications in the construction of large-scale quantum networks based on the giant-atom waveguide-QED systems.