bashir mojaveri

In this study, we introduce a new class of two-mode qutrit-like entangled states based on the `Near' coherent states. They link to a specific class of non-classical states, namely, photon added coherent states, which makes them capable candidates in quantum information processes. Based on these states, various superpositions such as the two-qubit entangled states, have been introduced and studied by various authorities, which is evidence for their valuable quantum properties. Therefore, based on the above-mentioned relationship and the emergence of controllable non-classical properties of these states, in this work, we seek to analyze the effect of adding photons to two-qutrit entangled states. For this purpose, we present a general analysis of non-classical properties such as the photon statistics and entanglement with emphases on the control role of the shift parameter of these states. We apply the generalized I-concurrence measure to quantify the entanglement and the condition in which quantum entanglement can be enhanced and maximized. Comparing with some cases already discussed in the literature, we can see that the photon addition, which is equivalent to selecting a specific shift parameter, plays an important role in non-classical effects, and this operation can be applied to enhance and preserve the entanglement.

In this paper, a Hamiltonian model that includes interaction of two two-level atoms with a codirectional Kerr nonlinear coupler via the Raman non-degenerate two-photon transition is introduced. The atomic interaction is assumed in the dipole-dipole form and the total system is also in thermal equilibrium with the environment. The total excitation number operator, as the constant of motion of system provides a decomposition of the Hilbert space of system into direct sums of invariant subspaces. As a result, the representation of the Hamiltonian becomes block-diagonal matrix. By diagonalizing each of blocks, we obtain eigenvalues and corresponding eigenstates of the Hamiltonian. Then we obtain thermal state of system in the whole Hilbert space and within its excitation subspaces. We quantify thermal entanglement between the atoms in the Hilbert space of system and within its excitation subspaces using the measure of concurrence. Finally, the effect of temperature and system parameters on the degree of thermal entanglement is investigated. The results show that in the subspaces with odd excitation number, the atomic thermal entanglement is thermally robust and remains constant.