The effects of nonlinear couplings and external magnetic field on the thermal entanglement in a two-spin-qutrit system

Abstract

We investigate the effects of nonlinear couplings and external magnetic field on the thermal entanglement in a two-spin-qutrit system by applying the concept of negativity. It is found that the nonlinear couplings favor the thermal entanglement creating. Only when the nonlinear couplings |K| are larger than a certain critical value does the entanglement exist. The dependence of the thermal entanglement in this system on the magnetic field and temperature is also presented. The critical magnetic field increases with the increasing nonlinear couplings constant |K|. And for a fixed nonlinear couplings constant, the critical temperature is independent of the magnetic field B.

Quantum Phase Transitions and Heat Capacity in a two-atoms Bose-Hubbard Model

“…1 of Ref. [31]) It is easy to interpret the occurrence of the intermediate phase at N = 1 2 as due to the magnetic field assisted competition between the quadratic term and the linear one when both γ and τ are positive. To appreciate this point it is enough to note that the two-atom system, when τ > 0, tends to minimize its total energy assuming j = 0 (maximally entangled state), whilst it tends to maximize both j and |M | (factorized state) when γ > 0 in presence of a magnetic field.…”

“…The addition of the term proportional to τ to the model of Ref. [31] is at the origin of an intermediate phase (plateau of the negativity, N = 1…”

“…Recently the role of the nonlinear effective coupling between the two atoms on the thermal entanglement has been qualitatively investigated. In detail it has been found that the quadratic interaction term favors the thermal entanglement that on the other hand exists only for absolute values of the quadratic parameter γ < 0 larger than a critical value γ c [31]. In presence of an external magnetic field (ω = 0) the system shows two different phases, one correspondent to N = 1 and the other one to N = 0, and the value of γ c at which the phase transition takes place is dependent on ω.…”

Effect of Intrinsic Decoherence of Milburn's Model on Entanglement of Two-Qutrit States

“…The system is composed of two wells with one spin-1 atom in each well in the optical lattice, which can be formed by three orthogonal laser beam. If the effective Hamiltonian of the Bose-Hubbard form [20] is used to describe the system, just investigating the effect of nonlinear coupling and that of the external magnetic field applied to the system, for finite but small hopping time, we can get, [21,22]…”

Effects of Nonlinear Couplings on Entanglement in a Two-Qutrit HeisenbergXXXChain under an Inhomogeneous Magnetic Field

“…As an important source of entanglement, thermal entanglement has been widely investigated in many previous studies. Such as, Zhou [12] and Zhang [13] studied the influence of nonlinear couplings on spin-1 Heisenberg systems. But only the uniform magnetic field was considered in their studies; they did not discuss the effects of inhomogeneous magnetic fields on the entanglement of two qutrit systems with nonlinear couplings.…”