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ACTA PHOTONICA SINICA

Quantum Discord in The System of W-like States Atoms Interacting with Three Coupled Cavities Connected by Two Optical Fibers

Qiu Chang-don

Published Jan 1, 2015• 0 citations
OpenAlex

Abstract

The Geometrical Quantum Discord(GQD)is an effective measure of quantum correlation in quantum systems.The system of W-like states atoms interacting with three coupled cavities connected by two optical fibers was investigated.In the case of like-W state,optical cavities and fiber field are all in vacuum state initially.The evolution of the state vector of the system is given.GQD is adopted to quantify the degree of quantum discord between atoms.The GQD dynamics between atoms are discussed.The influences of coupling constant between cavity and fiber on geometrical quantum discord between atoms are discussed.The results show that GQD between atoms is strengthened with increasing of coupling constant between cavity and fiber.

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Physica Scripta•May 16, 2017•51 citations
The Geometrical Quantum Discord(GQD)is an effective measure of quantum correlation in quantum systems.The system of W-like states atoms interacting with three coupled cavities connected by two optical fibers was investigated.In the case of like-W state,optical cavities and fiber field are all in vacuum state initially.The evolution of the state vector of the system is given.GQD is adopted to quantify the degree of quantum discord between atoms.The GQD dynamics between atoms are discussed.The influences of coupling constant between cavity and fiber on geometrical quantum discord between atoms are discussed.The results show that GQD between atoms is strengthened with increasing of coupling constant between cavity and fiber.
Geometrical quantum discord (GQD) is an effective measure of quantum correlation in quantum systems. We study GQD dynamics in an atom-cavity-fiber system. GQD between atoms and that between cavities are investigated. The influences of coupling constant between cavity and fiber and the intensity of the cavity field on GQD are discussed. Results show that GQD between atoms and that between cavities all display periodical evolutions, and their evolution frequencies increase with increasing coupling constant between cavity and fiber. On the other hand, the GQD between atoms and that between cavities are all strengthened with increasing intensity of the cavity field.
The geometrical quantum discord (GQD) is an effective measure of quantum correlation in quantum systems. We have studied GQD dynamics of the system comprising two two-level atoms resonantly interacting with two coupled cavities. GQD between atoms and that between cavities are investigated. The influences of coupling constant between cavities and initial entanglement between atoms on GQD are discussed. Results obtained using a numerical method show that GQD between atoms is strengthened, and GQD between cavities is weakened with increasing initial entanglement between atoms. On the other hand, the evolution regularity of GQD between atoms and that between cavities are all strengthened with increasing coupling constant between cavities.
Abstract Using quantum discord (QD) and geometric quantum discord (GQD), quantum correlation dynamics is investigated for two coupled qubits within a multiqubit interacting system in the zero-temperature bosonic reservoir, under both weak and strong qubit-reservoir coupling regimes. The multiqubit system is connected with either a common bosonic reservoir (CBR) or multiple independent bosonic reservoirs (IBRs). In the CBR case, our findings indicate that both QD and GQD can be strengthened by increasing the number of qubits in the multiqubit system. Furthermore, we study the steady state QD and GQD in the strong coupling regime, and find that the stable value in the long-time limit is determined exclusively by the number of qubits. The evolution period of QD and GQD gets longer as the dipole–dipole interaction (DDI) strength increases, which helps prolong the correlation time and thus preserves the quantum correlation under the weak coupling regime. Further analysis reveals notable differences between the CBR and IBRs scenarios. In the IBRs case, the decay of QD and GQD becomes slower compared to the CBR case, with both measures tending to zero at a reduced rate. Moreover, GQD consistently exhibits lower values than QD in both scenarios. These findings provide valuable insights into the selection of appropriate correlation measurement techniques for quantifying quantum correlations.
Quantum entanglement plays a key role in quantum information and quantum computation and thus attracts much attention in many branches of physics both in theory and in experiment. But recent studies revealed that some separable states (non-entangled state) may speed up certain tasks over their classical counterparts and may also possess certain kinds of quantum correlations. For example, geometric quantum discord, which is a more general quantum correlation measure than entanglement, can be nonzero for some separable states. From a practical point of view, it is proposed that the geometric quantum discord be responsible for the power of many quantum information processing tasks. In order to capture such correlations, Ollivier and Zurek introduced quantum discord, which measures the discrepancy between two natural yet different quantum analogues of two classically equivalent expressions of mutual information. However, the calculation of quantum discord is based on numerical maximization procedure, and there are few analytical expressions even for a two-qubit state. In order to obtain the analytical results of quantum discord, a geometric measure of quantum discord which measures the quantum correlations through the minimum Hilbert-Schmidt distance between the given state and zero discord state is introduced. Geometric quantum discord is defined as an effective measure of quantum correlation, and the geometric quantum discord through the minimal distance between the quantum state and the set of zero-discord states in a bipartite quantum system can be worked out. In this paper, by using the geometric quantum discord measurement method, the geometric quantum discord in Tavis-Cummings model is investigated, and the influences of the initial state purity, entanglement degree, dipole-dipole coupling intensity between two atoms, and field in the Fock state on the evolution characteristic of geometric quantum discord are analyzed. The results show that the geometric quantum discord appears periodically. It initially decreases to a minimum value, and then turns out to be increased for different initial states. The rigorous analysis and numerical results reveal that when we take a suitable initial state, the geometric quantum discord of two atoms can be kept in correlation. When the atoms are in the different initial states, the quantum properties of the system are significant. The photon number of the field can lead the quantum discord to be weakened. Geometric quantum discord can be increased by increasing the cavity photon number and the dipole-dipole coupling intensity. Geometric quantum discord can be enhanced obviously by increasing the strength of the dipole-dipole coupling interaction. The conclusions may conduce to the understanding of quantum correlation for the other systems from the view of geometric quantum discord.
Abstract We explore the quantum correlations for two coupled quantum wells. Each quantum well is inside a semiconductor microcavity. The two cavities are connected by an optical fiber. The study of quantum correlations, namely the geometric quantum discord, measurement-induced non-locality and negativity, reveals sudden death and sudden birth phenomena. These effects depend not only on the initial states, coupling strengths of the cavity–fiber and cavity–exciton constants, but also on the dissipation rates of the semiconductor microcavities. We show that the coupling constants control the quantum correlations.