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Chinese Physics B

Controlling quantum discord dynamics in cavity QED systems by applying a classical driving field with phase decoherence

Yi Qian, Jing‐Bo Xu

Published Mar 1, 2012• 10 citations
Publisher

Abstract

We investigate a two-level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non-interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.

DOI
10.1088/1674-1056/21/3/030305

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We investigate a two-level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non-interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.
We investigate the quantum discord dynamics in a cavity quantum electrodynamics system, which consists of two noninteracting two-level atoms driven by independent optical fields and classical fields, and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical fields. It is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving fields. Finally, the influence of the classical driving field on the fidelity of the system is also examined.
We investigate the quantum discord dynamics of two effective two-level atoms independently interacting with two quantized field modes through a Raman interaction in the presence of phase decoherence. The influence of the phase decoherence and detuning on the evolution of the quantum discord and entanglement between two atoms is discussed. It is found that the quantum discord is more robust than the entanglement under the phase decoherence, and the amount of discord and entanglement between two atoms can be increased by adjusting the detuning.
We investigate the phenomenon of sudden transition between classical and quantum decoherence in the study of quantum discord for a dissipative cavity QED system, which consists of two noninteracting two-level atoms, each trapped in a dissipative cavity. It is found that the quantum discord between the two atoms, which are prepared initially in the X-type quantum states, is not destroyed by the dissipation of the cavities for a finite time interval, and the stationary quantum discord can arise in the interaction of atoms with cavities as the time approaches infinity. The transition time is sensitive to the initial state parameter of the two atoms and the mean photon number of the coherent field. Interestingly, the quantum discord between the two atoms is completely unaffected by the dissipation of the cavities if we choose the suitable value of the ratio, which depends on the decay rate of the two cavities and the atom-field coupling constant.
We investigate the quantum discord dynamics of two noninteracting two-level atoms, each trapped in a single-mode optical cavity which is filled with a nonlinear Kerr-like medium. It is found that quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution. Furthermore, we explore the influence of the nonlinear Kerr-like medium on the dynamics of quantum discord, quantum mutual information, and classical correlation of two atoms. It is shown that the amount of quantum discord, quantum mutual information, and classical correlation of two atoms can be improved by adjusting the value of the Kerr medium. Finally, we also study the effect of phase dissipation on this system by making use of the Monte Carlo wavefunction method.
Abstract Quantum discord, an appropriate measure of quantum correlation, is analyzed in a two-mode Gaussian state of the cavity field evolved by a system of quantum beat laser. In the laser system, two arbitrary single-mode Gaussian states of the cavity fields and an external classical field couple to the atomic lasing medium. We calculate the time-dependent expression for the quantum discord both analytically and numerically, by following the reduced density matrix equation of the resulting cavity field. In this framework, we investigate the generation and control of Gaussian quantum discord in the two-mode Gaussian state of the cavity field at the output in terms of the purity and non-classicality of the two input cavity modes, the Rabi frequency of the classical driving field, the relative phase of the coupling parameters, and the damping rates of the cavity modes. The behaviour of quantum discord appears oscillatory due to the quantum beats in the output cavity field developed by the classical driving field in the medium as time passes. Moreover, we find that quantum discord switches on and off while adjusting the relative phase of the coupling parameters. Analysis of the analytical results agrees well with our numerical simulations.