In this paper we study the quantum entanglement of two identical qubits which interact with electromagnetic field and each other by time-dependent dipole-dipole interaction. We develop original method in path integral approach for numerical calculation of density matrix and Peres-Horodecki parameter (the measure of qubits entanglement). By the use of obtained equations we investigate the dependence of quantum entanglement on dipole-dipole interaction amplitude and frequency as well as qubits phase difference. The results indicate on possibility of high-entanglement states exiting and long-time non-destructive control of them.
We study the evolution of quantum entanglement in the model of two identical qubits interacting with a singlemode laser field. The density matrix and Peres-Horodecki parameter are calculated within the frameworks of path-integral formalism. The quantum entanglement measure is shown to be strongly dependent upon the phase difference between the laser radiation acting on each cubit. This observation may offer the possibility of quantum entanglement stationary control by varying the distance between the qubits.
We study the problem of rotational excitation of molecules by an ultrashort laser pulse sequence. Recent experimental investigations [Phys. Rev. Lett. 109, 043003 (2012)] shows that there are quantum resonances in rotational dynamics of dinitrogens molecules for some values of pulse train period. We describe these results theoretically. Physical parameters of ultrashort laser pulse sequence for effective selective rotational excitation of dinitrogens isotopes were defined by numerical simulations.