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Quantum Reports

Generation of Entanglement between Two Two-Level Atoms Coupled to a Microtoroidal Cavity Via Thermal Field

Emilio H. S. Sousa, José Antonio Roversi

Published Jul 8, 2020• 2 citations
Publisher

Abstract

We investigate the entanglement dynamics of a system comprising a pair of two-level dipole-dipole interacting atoms coupled to a microtoroidal resonator. Each atom is individually coupled with the two counter-propagating whispering gallery modes of the resonator through their evanescent fields. The atom-atom entanglement shown for several parameter sets of the system was obtained using the negativity. For ideal resonators, it is seen that the entanglement is correlated to the dipole-dipole interaction and the average number of photons when the modes of the resonator are prepared in a thermal state even at high temperatures. Further, for the non-ideal resonator case, where there is a small structural deformation of the microtoroidal structure that allows a direct coupling between the modes, a counter-intuitive result is presented. The imperfections also offer the advantage of generating maximally entangled states for a two-atom subsystem with maximum fidelity.

DOI
10.3390/quantum2030024

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We investigate the entanglement dynamics of a system comprising a pair of two-level dipole-dipole interacting atoms coupled to a microtoroidal resonator. Each atom is individually coupled with the two counter-propagating whispering gallery modes of the resonator through their evanescent fields. The atom-atom entanglement shown for several parameter sets of the system was obtained using the negativity. For ideal resonators, it is seen that the entanglement is correlated to the dipole-dipole interaction and the average number of photons when the modes of the resonator are prepared in a thermal state even at high temperatures. Further, for the non-ideal resonator case, where there is a small structural deformation of the microtoroidal structure that allows a direct coupling between the modes, a counter-intuitive result is presented. The imperfections also offer the advantage of generating maximally entangled states for a two-atom subsystem with maximum fidelity.
We theoretically investigate how the initial state influence the entanglement dynamics between two and three two-level atoms with dipole-dipole interaction (DDI) coupled to a whispering-gallery-mode (WGM) microtoroidal cavity. Two different cases, where the two atoms are coupled symmetrically or asymmetrically to the two WGMs through evanescent fields, are discussed in detail. Considering two types of initial states between the atoms and the symmetric regime, we show that for the initial entangled state, the sudden death and birth, as well as the freezing of the entanglement, can be obtained by adjusting both the scattering strength between the modes and the DDI, differently from the initial product state. Moreover, we note that the atomic entanglement generation is more susceptible to the scattering strength variation between the modes than to the DDI. In addition, for the asymmetric regime, the entanglement generation is strongly dependent on the atomic location and the scattering strength. Similar results are obtained for the case of three atoms coupled to a microtoroidal cavity, even in the presence of losses.
Understanding the dynamic evolution of quantum systems have a key role in understanding and applicability of phenomena involved in computing and quantum information. In this presentation, we discuss the quantum dynamics of a system comprising two atoms of two levels microtoroidal coupled to a resonator in different ways. In a first arrangement atoms are neighbors enough so that the dipolar interaction between them cannot be neglected. In a second situation is the generation of entanglement in the bad ring resonator regime”, where one of the atoms is not resonant with the modes of the resonator nor interacts with another atom, it only works as a deformation of the ring resonator. We show that the entanglement between the two atoms is strongly dependent on the dipolar interaction between the atoms and we have found an enhancement of the entanglement correlated to the average number of thermal photons when the modes of resonator are prepared in a thermal states. We have observed that depending on the preparation of initial state may occur phenomenon of death rise tangling between atoms. Depending upon the intensity of the mean number of photons in the thermal field and the coupling between the atoms with the resonator is possible to generate maximum entanglement between atoms even in the regime of high temperature.
We present an efficient scheme for the generation of entangled states of two spatially separated whispering-gallery-mode (WGM) micro-resonators which are coupled via 2 two-level atoms. Using an atom chain as bridges, we explore the possibility of generation, transfer as well as distributing quantum entanglement between the two cavities. We show that, for an initial preparation with the system having only one photon, the atoms can become periodically (and maximally) entangled while the intra-cavity modes in each cavity become periodically (partially) entangled. Interestingly, if the cavities are initially prepared with two photons, the dynamics can be tuned in such a way that the intra-cavity modes in each cavity become periodically entangled, reaching maximum entanglement, while the atoms remain unentangled during all time.
We investigate the entanglement properties of a system of two dipole-dipole coupled two-level atoms resonantly interacting with a two-mode thermal field in a high- Q cavity. We obtain the evolution operator for this system in an analytical form, and use it to evaluate the atom-atom entanglement through the calculation of the negativity. The results show that the atom-atom entanglement is dependent on cavity field intensity and dipole interaction strength. We find that the dipole interaction can produce a considerable amount of entanglement between the two atoms.
In this paper, we investigated the entanglement dynamics between two two-level natural or artificial atoms interacting with a thermal one-mode field of lossless cavity taking into account the direct dipole-dipole and Ising coupling. We obtained the exact solution for time-dependent density matrix and calculated atom-atom negativity. The results showed that for dipole-uncoupled atoms and resonant atoms-field interaction the entanglement greatly enhances with Ising coupling increasing. In contrast, for model with non-zero detuning the Ising coupling has almost no effect on the degree of entanglement. We also derived that for resonant interaction and dipole-coupled atoms the anti-Ferromagnetic coupling produces a slightly higher degree of entanglement in comparison with the Ferromagnetic coupling. For entangled initial atomic states we obtained that Ising coupling interaction has effect on entanglement behavior only for a model with large detuning values.