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-photon ENTANGLEMENT. 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.

In this paper, the quantum correlation of the 2- spin Heisenberg model systems with Dzyaloshinskii-Moriya interaction and in the presence of the external magnetic field is studied. Three types of the exchange interaction, XX, XY, and XZ interactions are considered . The THERMAL ENTANGLEMENT of these systems is investigated under the change of the external magnetic field. We found that the temperature behavior of three models is similar, although the critical temperature is different. Also, we investigated the effect of the external magnetic field on the negativity of the system. We observed that all three models have the critical magnetic field in which the negativity of the system becomes zero. In fact, the anisotropic Heisenberg interaction can affect the critical temperature and critical magnetic field of the two- spin systems.

In this paper, THERMAL ENTANGLEMENT in four and five-qubit spin-star networks evolved by an XXX Hamiltonian model is studied. We examine the effect of temperature, magnetic field and coupling constant on the concurrence. We will show that the ENTANGLEMENT is decreased by increasing the temperature and the number of qubits. Also, we investigate quantum teleportation via a couple of spin-star networks in a THERMAL state. The average of fidelity as a function of temperature, magnetic field, and coupling constant is analyzed, too. It will be observed that as the temperature increases, the fidelity first decreases and then tends to a constant value. Moreover, with the increase of the external magnetic field, the average fidelity first increases and then gradually decreases, and in a certain amount of magnetic field, the average fidelity becomes zero. In addition, as the number of qubits increases, fidelity decreases with temperature. The results indicate that mean fidelity increases with increasing coupling constant.

We analyze the role of bath temperature, coherence and ENTANGLEMENT on excitation transfer in a spin chain induced by the environment. In Markovian regime, we show that coherence and ENTANGLEMENT are very sensitive to bath temperature and vanish in time in contrary to the case of having zero-temperature bath. That is while, finding the last qubit of the chain in excited state increases by increasing the bath temperature. The obtained results show the destructive role of temperature on coherence and ENTANGLEMENT and confirm that these quantum mechanical features cannot affect probability of finding the last qubit in excited state.

In this paper, a Hamiltonian model, which includes the 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 to be 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 the motion of the 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 a block-diagonal matrix. By diagonalizing each of the blocks, we obtain eigenvalues and the corresponding eigenstates of the Hamiltonian. Then we obtain the THERMAL state of the system in the whole Hilbert space and within its excitation subspaces. We quantify the THERMAL ENTANGLEMENT between the atoms in the Hilbert space of the system and within its excitation subspaces using the measure of the 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 an odd excitation number, the atomic THERMAL ENTANGLEMENT is THERMALly robust and remains constant.

In the present work we use the negativity to study the effect of Rashba parameter on the THERMAL ENTANGLEMENT of electronic spin and subband states inside a quasi-one-dimensional Rashba nanowire, in a perpendicular uniform magnetic field. We assume that the nanowire is held at a temperature T, so that both spin and subband states, with definite probabilities, are present. The partially transposed density matrix is shown to be block-diagonal, whose eigenvalues are readily obtained. By analyzing these eigenvalues, it is shown that, even at high temperatures there always exist negative eigenvalues, so that the system of electronic spin and subbands inside a Rashba nanowire is never separable. Moreover, we show that the negativity, at certain temperatures, exhibits maxima. The temperatures at which the ENTANGLEMENT is maximal strongly depend upon the Rashba parameter. We further present graphs of negativity as functions of temperature for different Rashba parameters, showing that the maximal ENTANGLEMENT occurs at lower temperatures for larger Rashba parameters. The novel results in the present article shows how the behavior of spin-subband THERMAL ENTANGLEMENT depends upon an externally controllable agent.

In 2006, Ryu and Takayanagi (RT) pointed out that (with a suitable cutoff) the ENTANGLEMENT entropy between two complementary regions of an equal-time surface of a d+1-dimensional conformal field theory on the conformal boundary of AdS{d+2} is, when the AdS radius is appropriately related to the parameters of the CFT, equal to 1/4G times the area of the $d$-dimensional minimal surface in the AdS bulk which has the junction of those complementary regions as its boundary, where $G$ is the bulk Newton constant. (More precisely, RT showed this for d=1 and adduced evidence that it also holds in many examples in d>1. ) We point out here that the RT-equality implies that, in the quantum theory on the bulk AdS background which is related to the boundary CFT according to Rehren's 1999 algebraic holography theorem, the ENTANGLEMENT entropy between two complementary bulk Rehren wedges is equal to one 1/4G times the (suitably cut off) area of their shared ridge. (This follows because of the geometrical fact that, for complementary ball-shaped regions, the RT minimal surface is precisely the shared ridge of the complementary bulk Rehren wedges which correspond, under Rehren's bulk-wedge to boundary double-cone bijection, to the complementary boundary double-cones whose bases are the RT complementary balls. ) This is consistent with the Bianchi-Meyers conjecture--that, in a theory of quantum gravity, the ENTANGLEMENT entropy, S between the degrees of freedom of a given region with those of its complement takes the form S = A/4G (plus lower order terms)--but only if the phrase `degrees of freedom' is replaced by `matter degrees of freedom'. It also supports related previous arguments of the author--consistent with the author's `matter-gravity ENTANGLEMENT hypothesis'--that the AdS/CFT correspondence is actually only a bijection between just the matter (i. e. non-gravity) sector operators of the bulk and the boundary CFT operators.

In this work, we explore the holographic ENTANGLEMENT entropy with an infinite strip region of the boundary in Horndeski gravity. In our prescription we consider the spherically and planar topologies black holes in the AdS4/CFT3 scenario. In such framework, we show the behavior of the ENTANGLEMENT entropy in function of the Horndeski parameters. Such parameters modify the information store of subsystem A, especially when the parameter $gamma$ increases the information about the subsystem will also increase or decrease when it decreases. Thus, with this scheme we compute the “first law of ENTANGLEMENT thermodynamics” in Horndeski gravity and we show that a very small subsystem obeys the analogous property of the first law of thermodynamics if we excite the system.

In this work‎, ‎we explore the ENTANGLEMENT entropy equipped with the $\kappa$-algebra‎. ‎This ENTANGLEMENT entropy is computed through the geometric setup as performed by Hartman-Maldacena‎, ‎which‎, ‎in their prescription‎, ‎finds that the entropy grows linearly in time‎. ‎In our case‎, ‎we show that the $\kappa$-algebra embedding provides a richer scenario where the third-order corrections in time added from $\kappa$-algebra to ENTANGLEMENT entropy imply that the growth of quantum correlations between subsystems is more intricate than a simple linear increase into the dynamics of black hole THERMALization and quantum information flow‎. ‎In the context of holography‎, ‎such corrections suggest that the THERMALization process is not instantaneous but involves higher-order interactions between subsystems‎.