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arXiv:0912.1468 · New Journal of Physics

Entanglement versus quantum discord in two coupled double quantum dots

F. F. Fanchini, L. K. Castelano, A. O. Caldeira

Published Jul 5, 2010• 92 citations
arXivHTMLPDF

Abstract

We study the dynamics of quantum correlations of two coupled double quantum dots containing two excess electrons. The dissipation is included through the contact with an oscillator bath. We solve the Redfield master equation in order to determine the dynamics of the quantum discord (QD) and the entanglement of formation (EoF). Based on our results, we find that the QD is more resistant to dissipation than the EoF for such a system. We observe that this characteristic is related to whether the oscillator bath is common to both qubits or not and to the form of the interaction Hamiltonian. Moreover, our results show that the QD might be finite, even for higher temperatures in the asymptotic limit.

DOI
10.1088/1367-2630/12/7/073009

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We study the dynamics of quantum coherence and quantum correlations in two semiconductor double-dot molecules separated by a distance and indirectly coupled via a transmission line resonator. Dominant dissipation processes are considered. The numerical results show the sudden death of entanglement and the robustness of quantum discord to sudden death. Furthermore, the results indicate the dephasing processes in our model can lead in the revival and decay of coherence and discord with the absence of entanglement for certain initial states. By observing the dynamics of coherence versus discord for different initial states, we find that the similarities and differences of coherence and discord are not only related to the dependance of discord on optimizing the measurement set, but more importantly to the coherences in individual qubits which are captured by the adopted coherence measure.
Abstract In this paper, we study the geometric quantum discord dynamics of the double quantum dot charge qubit in the non-Markovian environment. We apply the non-perturbative non-Markovian quantum state diffusion method to obtain the exact master equation of the double quantum dot system coupled to two independent non-zero temperature electronic baths. Then, we use this master equation to investigate the effects of non-Markovianity, inter-dot coupling strength and bath temperature on the dynamics of geometric quantum discord. Our studies show that the geometric quantum discord of a double quantum dot system can be modified and enhanced in some cases via these factors.
The quantum entanglement, discord, and coherence dynamics of two spins in the model of a spin coupled to a spin bath through an intermediate spin are studied. The effects of the important physical parameters including the coupling strength of two spins, the interaction strength between the intermediate spin and the spin bath, the number of bath spins and the temperature of the system on quantum coherence and correlation dynamics are discussed in different cases. The frozen quantum discord can be observed whereas coherence does not when the initial state is the Bell-diagonal state. At finite temperature, we find that coherence is more robust than quantum discord, which is better than entanglement, in terms of resisting the influence of environment. Therefore, quantum coherence is more tenacious than quantum correlation as an important resource.
The dissipative dynamics of classical correlation(CC), quantum discord(QD) and entanglement (QE) of two qubits in two-side and one-side decoherence models are inves- tigated under Markovian environments. We find the sudden change QD as well as CC and sudden death of entanglement (ESD). The results show that QD and QE decay faster with the increasing of squeezing parameter r; the dipole-dipole interaction W under two-side decoherence leads to the oscillation of quantum discord and concurrence for initial non- eigenstates; while in all cases when entanglement suddenly disappears, quantum discord keeps nonzero under same conditions.