Quantum discord dynamics in the presence of initial system–cavity correlations

Abstract

We analyze the roles of initial correlations between the two-qubit system and a dissipative cavity on quantum discord dynamics of two qubits. Considering two initial system-cavity states, we show that the initial system-cavity correlations not only can initially increase the two-qubit quantum discord but also would lead to a larger long-time quantum discord asymptotic value. Moreover, quantum discord due to initial correlations is more robust than the case of the initial factorized state. Finally, we show the initial correlations' importance for dynamics behaviors of mutual information and classical correlation.

The classical-quantum boundary for correlations: Discord and related measures

“…Furthermore, discord need not decay to zero in the asymptotic limit (Fanchini et al, 2010a), since an environment sometimes preserves certain types of correlations. (Zhang et al, 2011d) give an example of this by considering two atoms coupled to a common-dissipative cavity mode: the evolution is strongly dependent on the initial correlations, and when the initial state includes a contribution from the subradient state the discord tends to a finite value. The choice of initial state can have other effects too: a model for which two atoms subject to independent and collective spontaneous emission, as well as the dipole-dipole inter-action is explored in , and it is shown that the speed of decay of several types of quantum correlations can be simultaneously and strongly enhanced by local unitary transformations of the initial state.…”

Quantum discord between two moving two-level atoms

“…It can be seen that, the time evolutions of the quantum discord and entanglement are similar, and exhibit the periodic dynamics with the same period of 2π/ . It can be understood by using equation (8). From equation (8), θ( ) = 1 1 − cos( ) , we observe that θ( ) is a periodical function on the scaled time with a period of 2π/ .…”

“…When considering an initial entangled state exposed to * E-mail: huyaohua1@sina.com local noisy environments, the entanglement may decrease abruptly and nonsmoothly to zero in a finite time, which is called entanglement sudden death (ESD) [5][6][7]. However, recent researches have shown that entanglement is not the only measure of quantum correlation, and a new but promising candidate is the quantum discord [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Quantum discord, first introduced by Ollivier and Zurek [16], is defined as the difference between the total correlation and the classical correlation with the following expression (ρ AB ) = (ρ AB ) − (ρ AB )…”

Decay of two-qubit correlations in the squeezed Bloch channel

“…The quantum correlation measured by the quantum discord [16,17] is also important in quantum information processing. Hence the quantum discord has recently been investigated by many authors [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Although the quantum discord is, in general, very difficult to calculate, an exact and analytical expression can be obtained for the two-qubit X-state including the Werner state and the Bell diagonal state [18,23,24].…”