arXiv subjects

Zhi-Guo Lü

Publications and source records attributed to Zhi-Guo Lü.

2 recordsLinked to original sources

arXiv2007

Dynamics of two qubits in a spin-bath of Quantum anisotropic Heisenberg XY coupling type

The dynamics of two 1/2-spin qubits under the influence of a quantum Heisenberg XY type spin-bath is studied. After the Holstein-Primakoff transformation, a novel numerical polynomial scheme is used to give the time-evolution calculation of the center qubits initially prepared in a product state or a Bell state. Then the concurrence of the two qubits, the $z$-component moment of either of the subsystem spins and the fidelity of the subsystem are shown, which exhibit sensitive dependence on the anisotropic parameter, the temperature, the coupling strength and the initial state. It is found that (i) the larger the anisotropic parameter $γ$, the bigger the probability of maintaining the initial state of the two qubits; (ii) with increasing temperature $T$, the bath plays a more strong destroy effect on the dynamics of the subsystem, so does the interaction $g_0$ between the subsystem and the bath; (iii) the time evolution of the subsystem is dependent on the initial state. The revival of the concurrence does not always means the restore of the state. Further, the dynamical properties of the subsystem should be judged by the combination of concurrence and fidelity.

cond-mat.stat-mech↗

arXiv2007

Quantum dynamics of double-qubits in a spin star lattice with an XY interaction

The dynamics of two coupled spins-1/2 interacting with a spin-bath via the quantum Heisenberg XY coupling is studied. The pair of central spins served as a quantum open subsystem are initially prepared in two types of states: the product states and the Bell states. The bath, which consists of $N$ (in the thermodynamic limit $N\to\infty$) mutually coupled spins-1/2, is in a thermal state at the beginning. By the Holstein-Primakoff transformation, the model can be treated effectively as two spin qubits embedded in a single mode cavity. The time-evolution of the purity, z-component summation and the concurrence of the central spins can be determined by a Laguerre polynomial scheme. It is found that (i) at a low temperature, the uncoupled subsystem in a product state can be entangled due to the interaction with bath, which is tested by the Peres-Horodecki separability; however, at a high temperature, the bath produces a stronger destroy effect on the purity and entanglement of the subsystem; (ii) when the coupling strength between the two central spins is large, they are protected strongly against the bath; (iii) when the interaction between the subsystem and the bath is strong, the collapse of the two spin qubits from their initial entangled state is fast.

quant-ph↗