Quantum discord for the general two-qubit case

Naihuan Jing, Bing Yu

王仲宵, 王波波

Ji-Bing Yuan, Le‐Man Kuang, Jie‐Qiao Liao

We study analytically the dynamic behaviours of quantum correlation measured by a quantum discord between two uncoupled qubits, which are immersed in a common Ohmic environment. We show that the quantum discord of the two non-interacting qubits can be greatly amplified or protected for certain initially prepared X -type states in the time evolution. In particular, it is found that stable amplification of the quantum discord exists for the case of two identical qubits, and the quantum discord can be protected for the case of two different qubits with a large detuning. It is also indicated that in general a sudden change of the quantum discord occurs in the time evolution at a critical time point t c , and the discord amplification and protection may occur only in the time interval for certain X -type states. This sheds new light on the creation and protection of quantum correlation.

Jianming Zhou, Xiaoli Hu, Naihuan Jing

Qi-Wen He, Zhi He, Yu Chen

Abstract We investigate the protection of the quantum discord of two qubits, individually originated by two generalized amplitude-damping models. Here, each generalized amplitude-damping model consists of N non-interacting qubits interacting with a common zero-temperature reservoir. First, for initial states with extended Werner-like states, we find that the robust quantum discord of two qubits against decoherence can be obtained by controlling the number of qubits in the reservoir. More interestingly, we find that a quantum beat for quantum discord can occur when both the number of qubits in each reservoir is large and when the number of qubits have a tiny difference, even in the resonant case. Our results shed new light on the protection of quantum discord by means of a quantum-reservoir engineering approach in quantum-information processing.

Jing Nie, Xiu-Yi Yang, Chong Li