In this paper we study the properties of photon-photon thermal entanglement occurring in a nonlinear optical cavity. The photons are thermally produced inside a nonlinear cavity that couples the two modes via first and third order susceptibilities. Diagonalizing the Hamiltonian of the system, the thermal density matrix and, consequently, the partially transposed one are obtained. The negative eigenvalues of the latter are then calculated, leading to the negativity as a measure of photon-photon entanglement. Our results show that the two photons are separable at absolute zero. As the temperature increases, the negativity exhibits a maximum whose value strongly depends on the medium characteristics and then asymptotically vanishes.
In this paper we study the properties of photon-photon thermal entanglement occurring in a nonlinear optical cavity. The photons are thermally produced inside a nonlinear cavity that couples the two modes via first and third order susceptibilities. Diagonalizing the Hamiltonian of the system, the thermal density matrix and, consequently, the partially transposed one are obtained. The negative eigenvalues of the latter are then calculated, leading to the negativity as a measure of photon-photon entanglement. Our results show that the two photons are separable at absolute zero. As the temperature increases, the negativity exhibits a maximum whose value strongly depends on the medium characteristics and then asymptotically vanishes.
The entanglement of Λ-type three-level atoms and thermal photons in a nanocavity inside a double-band photonic crystal is studied. The partially transposed density matrix and, consequently, the negativity, as a measure of entanglement, are determined at a temperature T . By analyzing the eigenvalues of the partially transposed density matrix, we show that the thermal atom–field states remain coherent for all temperatures. Furthermore, plots of the negativity indicate that at a definite temperature, which strongly depends upon the location of the photonic band gaps, the entanglement is maximal. How the location of the photonic band gaps, relative to the atomic transition frequencies, affects this temperature is also addressed.
In this work we investigate the thermal entanglement between two-level atoms and photons in a nonlinear cavity. We consider intensity-dependent couplings and calculate the negativity, as a measure of atom-photonentanglement. The cavity is assumed to be at a temperature T, so that all number of photons, and at the same time, both atomic states, with definite probabilities, are present. We then demonstrate a condition under which the intensity-dependent coupling leads to entanglement. It is also shown that, as in the case of linear Jaynes- Cummings model, the thermal states of atoms and photons are never separable.
The entanglement between two two-level atoms (qubits) interacting not-resonantly with a one mode of thermal field in a lossless cavity via effective degenerate two-photon transitions is investigated. Based on the exact solution for the time-dependent density matrix of the system under consideration, negativity is calculated as a measure of the entanglement of atoms. The influence of a detuning on the dynamics of entanglement of atoms for separable and entangled initial atomic states and thermal cavity state is investigated.
In this paper the time evolution of von Neumann entropy as a measure of entanglement between a two-level atom and the photonic coherent states in a cavity is studied. The atom-photon interaction occurs in the presence of a centrosymmetric medium which makes the photonic cavity mode couple with itself via the third order susceptibility. In the present system the atom-photon interaction is assumed to follow the linear Jaynes-Cummings model while the photonic selfcoupling is due to presence of a centrosymmetric medium and occurs via the third order susceptibility. After calculating the time-evolution operator, the von Neumann entropy, as a function of time, is determined. It is shown that an increase of photonic self-coupling leads to decreasing of entanglement. Furthermore, the role of atom-photon detuning on the entanglement behavior is also addressed.
In the present study, temporal behavior of entanglement between photonic binomial distributions and a two-level atom in a leaky cavity, in equilibrium with the environment at a temperature T, is studied.In this regard, the master equation is solved in the secular approximation for the density matrix, when the initial photonic distribution is binomial, while the atomic states obey the Boltzmann distribution.The atom-photon density matrix so calculated is then used to compute the negativity, as a measure of entanglement.The behavior of atom-photon entanglement is, consequently, determined as a function of time and temperature.To justify the behavior of atom-photon entanglement, moreover, we employ the total density matrix to compute and analyze the time evolution of the initial photonic binomial probability distribution.Our results, along with representative figures reveal that the atomphoton degree of entanglement exhibits oscillations while decaying with time and asymptotically vanishes.It is further demonstrated that an increase in the temperature gives rise to a decrease in the entanglement.The finer characteristics of the temporal behavior of the corresponding probability distribution and, consequently, the atom-photon entanglement is also given and discussed.
In this paper, we study the quantum interaction between a moving two-level atom and a single-mode quantized field in an optical cavity with degenerate multi-photon transition, in the presence of intensity-dependent coupling and thermal effect. We introduce the appropriate Hamiltonian of the system, and we adopt the initial condition of subsystems, in which the atom is prepared in an arbitrary superposition of ground and excited states, and the field is considered in a thermal state. Consequently, we determine the density matrix of the entire system at any given time. We further assess some of the most important quantum properties, such as quantum coherence, sub-Poissonian statistics, and phase-space nonclassicality by means of negativity of the Wigner quasiprobability distribution function. We then investigate the impact of intensity-dependent nonlinearity, thermal noise, atomic motion, and multi-photon transition on these quantum properties. The numerical results show that the nonclassicality criteria can be significantly influenced and controlled by the effects discussed above. Interestingly, increasing the mean thermal photon number, which highlights the thermal effect, can, in some cases, enhance the nonclassicality features of the system.