Effects of Dynamic Stark Shift on Quantum Information Fidelity in Two-photon Transition

He An-Zhi

By considering the dynamic Stark shift,the effects of dynamic Stark shift of level and the squeezed light field factorsγon the fidelity of quantum state are discussed.It is shown that the evolutions of the fidelity obviously exhibit the oscillations of quantum collapse and revival.Taking the Stark shift into consideration,a comparative study of the two processes for the fidelity is presented.The fidelities of the atom,the field and the system are higher than those in the absence of the dynamic Stark shift when manipulating and communicating quantum information.Meanwhile,the periodicities of the fidelity evolutions of atom,field and the system are modulated by the intensity of the initial light field,and the impulse of the oscillation of fidelity for the field become smaller.The energy between field and atom is influenced by the squeezed light field factors.

Mao Fa Fang, Xiang Liu

Tahira Nasreen

In this thesis, we investigate the effect of the dynamical Stark shift on the quantum electrodynamics of an atom undergoing two-photon transitions, interacting with a quantized radiation field in an ideal cavity. To begin with, we discuss the dynamics of the electromagnetic field and the atom in the presence of the Stark shift. We derive closed expressions for the second-order coherence function, quadrature variances, atomic population inversion and dipole squeezing under the approximation of a large initial photon number and coherent or squeezed field input. We show that for an atom initially in the ground state, the inclusion of Stark shift reduces the field squeezing as well as the antibunching. Both the population inversion and the dipole squeezing exhibit phase sensitivity in the presence of Stark shift and for a particular choice of the relative phase of the two atomic levels "trapping" occurs in a two-level atom and the dipole is modified in such a way that it is permanently squeezed. We then discuss the effect of the stark shift on the emission spectrum of an atom and the cavity field spectrum. The inclusion of Stark shift results in asymmetric vacuum field Rabi splitting. We also study the dynamics of the combined atom-field wave function in the presence of the Stark shift and show that both the electromagnetic field and the atom periodically evolve to pure states which are radically different from those in the absence of the Stark shift. Finally, we study the nondegenerate two-photon Jaynes-Cummings model (NTPJCM) in the presence of the Stark shift and show that the dynamics of the NTPJCM in the presence of Stark shift is qualitatively different from the case of the absence of the Stark shift and radically different from the case of degenerate two-photon JCM in the presence of Stark shift.

M. M. Ashraf

Eugene K. Bashkirov, Yu.A. Nikiforova

The influence of dynamical Stark shift on the entanglement between two atoms prepared in initial W-like states in Tavis — Cummings model with degenerate two-photon transitions has been investigated. The results show that effect of sudden death of entanglement the effect can be weakened for some initial states with taking into account the Stark shift.

David A. Cardimona, Vassilios I. Kovanis, M. P. Sharma