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Latin America Optics and Photonics Conference

Non-Classical effects of the interaction between one or more atoms coupled to a ring resonator

José Antonio Roversi

Published Jan 1, 2016• 0 citations
Publisher

Abstract

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.

DOI
10.1364/laop.2016.lth2b.1

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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 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.
In this paper, we investigate the entanglement between two two-level atoms non-resonantly in-teracting with a thermal field of a lossless one-mode resonator via degenerate two-photon transi-tions. On the basis of the exact solution of the time-dependent density matrix we calculate the negativity as a measure of atomic entanglement. We show that for separable initial atomic states a slight atom-field detuning may generate the high amount of atom-atom entanglement. The re-sults also show that for non-resonant atom-field interaction the entanglement induced by nonlin-ear two-photon interaction is smaller than that induced by one-photon interaction in contrast to the resonant interaction situation. For a Bell-type entangled initial atomic state we obtain that if the detuning increases, there is an appreciable decrease in the amplitudes of the negativity oscilla-tions. The results also show that elimination of the sudden death of entanglement for non-resonant two-photon atom-field interaction may take place.
The exact dynamics of a model consisting of two two-level atoms interacting with the electromagnetic field mode of an ideal resonator through degenerate Raman transitions are found for coherent and thermal field states. The exact solution is used to calculate atom-atom negativity. It is shown that for separable initial states of atoms, their interaction with the resonator field does not lead to the occurrence of atom-atom entanglement. It was found that for the Bell initial states of atoms in the case of a coherent resonator field, the effect of sudden death of entanglement takes place for large average values of the number of photons in the resonator, while in case of thermal noise, this effect is absent for any intensities of the resonator field.
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.
In this article, author investigated the dynamics of entanglement of two dipole-coupled natural or artificial two-level atoms (qubits) interacting nonresonantly with the intensive one-mode cavity thermal field. Author found an exact solution of the quantum Liouville equation for the full density matrix of the system two atoms + field mode for a coherent initial state of atoms in the dressed states representation. The full system density matrix is used to calculate the two-atom reduced density matrix and to calculate the quantitative criterion for atom-atom entanglement ‒ negativity. The results of computer simulation of the time dependence of negativity showed that in the case of a model with nonresonant interaction, the presence of initial atomic coherence leads to a significant decrease in the maximum degree of atomic entanglement, in contrast to the model with resonant interaction of atoms and a field. For the resonance model, the initial atomic coherence greatly enhances the degree of atomic entanglement.