Dynamics of quantum discord for two correlated qubits in two independent reservoirs at finite temperature

Abstract

We investigate decoherence-free evolution (DFE) of quantum discord (QD) for two initiallycorrelated qubits in two finite-temperature reservoirs using an exactly solvable model. We study QD dynamics of the two qubits coupled to two independent Ohmic reservoirs when the two qubits are initially prepared in X-type quantum states. It is found that reservoir temperature significantly affects the DFE dynamics. We show that it is possible to control the DFE and to prolong the DFE time by choosing suitable parameters of the two-qubit system and reservoirs.

Decay of two-qubit correlations in the squeezed Bloch channel

“…It has also been found that the quantum discord decays asymptotically to zero with time even in the case when the entanglement sudden-death takes place [19,22]. Furthermore, the time-dependence of the quantum discord changes abruptly [20,21,25,[30][31][32]. For example, the quantum discord remains unchanged in some time region and it decays with time in the other region.…”

“…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].…”

Quantum-discord-triggered superradiance and subradiance in a system of two separated atoms

“…In this sense, people need a more effective tool for well quantifying all quantum correlation including all the two-body entanglement and separable states. Fortunately, some of the recent work [1,2,[30][31][32][57][58][59] suggests that quantum discord is a useful tool to measure the nonclassical correlation for two-body quantum system. As a consequence, QD is a more general measure of nonclassical correlation than entanglement [1] and may exhibit different features from concurrence.…”

“…Fortunately, the state ρ in Eq. (7) is a particular case of X-states, whose QDs have been intensely investigated [30][31][32]57,58]. For this X-state, the nonclassical correlation of the Werner state can be quantified by quantum discord [1,2], which is calculated to be [57,58] …”

“…QD is considered to be a more general resource of quantum advantage than quantum entanglement in quantum information processing [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. QD has been investigated in a wider context [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] including entanglement-free quantum computation [3], quantum communication [11,[19][20][21][22], and quantum phase transitions in many-body physics [23,[25][26][27][28][29]32]. In this paper, we add superradiance and subradiance to the list of QD applications.…”