Population inversion and entanglement dynamics of two coupled qubits in cavity QED

Tao Wu, L. Ye

Fujun Zhang, Dongxin Wang, Kun Liu +1 more

Eied Mahmoud Khalil, A.‐B. A. Mohamed

An analytical solution is obtained when the Kerr medium and Stark shift are considered as nonlinear interaction terms to the system containing two-qubit and two-mode electromagnetic field from the parametric amplifier. Dynamics of the population inversion, cavity–qubit and qubit–qubit entanglements are analyzed under the unitary cavity–qubit interaction, the Kerr medium and the Stark shift. The population inversion of a qubit presents periodic revivals and collapses. The results show that the entanglement and the population inversion as well as the inversion have the same stable intervals, that is, the collapse intervals. It is found that the Kerr medium and the Stark shift may lead to reduction of the periods and the amplitudes of the population inversion and the cavity–qubit/qubit–qubit entanglement. The deteriorated qubit–qubit/cavity–qubit entanglement and the population inversion, due to the Kerr medium, may be increased by increasing the Stark shift and vice versa.

S. A. S. Musavi, Mohammad Kazem Tavassoly, S. Salimian

In this paper, the entanglement between two qubits that exist in two distinct cavities which are connected by an optical fiber is investigated by using the concurrence, while two-photon transitions and Kerr medium effect are also considered. Each cavity contains a qubit and a single-mode quantized field. The appearance of entanglement between the two qubits in the separate cavities originates from the presence of optical fiber. The obtained numerical results of the considered system show that, if the Kerr medium is large enough, the initial values of entanglement between the two qubits (which may have the maximum possible value, i.e. 1) can be approximately protected from the large amplitude fluctuations, so that acceptable stability is created. Also, qubit-field coupling and detuning effects are investigated and it is observed that symmetric coupling results in more stability of entanglement. Eventually, atomic population inversion is also studied and it is observed that it is controllable by considering different parameters.

Zeng-Zhao Li, Xian-Ting Liang, Xiao‐Yin Pan

Uzma Akram

This thesis examines the effect of quantum interference occuring in a three-level atom in the V-configuration, on a variety of optical effects such as controlled spontaneous emission, population trapping, lasing without population inversion, controlled field intensity and photon statistics. Calculations are carried out numerically via the master equation approach and analytically using dressed atom analysis. Various atom-laser coupling configurations are investigated and dressed states identified in each case. The system is shown to exhibit trapping states for a variety of atom-laser coupling configurations. Moreover, the thesis focuses on the effect of quantum interference on a cavity QED system. Three different cavity detunings with respect to the entangled atom-laser system are considered. It is shown in each case how the singly dressed entangled system interacts with the cavity field to form entangled doubly dressed structures. Again, the system is shown to exhibit population trapping states with dependence on the cavity damping rate in one of the detunings considered. In addition, photon statistics of the cavity field are calculated and shown to be sensitive to the degree of quantum interference. Interestingly, controlled field intensity and sub-Poissonian statistics are obtained for certain parameters of the two off-resonance cases considered