Shao-xiong Wu

Time-dependent decoherence-free subspace

With time-dependent Lindblad operators, an open system may have a time-dependent decoherence-free subspace (t-DFS). In this paper, we define the t-DFS and present a necessary and sufficient condition for the t-DFS. Two examples are presented to illustrate the t-DFS, which show that this t-DFS is not trivial, when the dimension of the t-DFS varies.

Uncertainty-induced quantum nonlocality

Abstract Based on the skew information, we present a quantity, uncertainty-induced quantum nonlocality (UIN) to measure the quantum correlation. It can be considered as the updated version of the original measurement-induced nonlocality (MIN) preserving the good computability but eliminating the non-contractivity problem. For 2 × d -dimensional state, it is shown that UIN can be given by a closed form. In addition, we also investigate the maximal uncertainty-induced nonlocality.

Quantum correlation measure in arbitrary bipartite systems

Quantum correlation with a novel definition is presented for an arbitrary bipartite quantum state in terms of the skew information of the complete set of rank-one orthogonal projectors. This definition not only inherits the good properties of skew information including the contractivity, but also shows a powerful analytic computability for a large range of states. In addition, the measure for a general state can be easily numerically obtained by the well-developed technique of the approximate joint diagonalization. As a comparison, we give both the analytic and the numerical quantum correlation for many high-dimensional states. The relation between our measure and quantum metrology is also analyzed.

The initial-state dependence of the quantum speed limit

The generic bound of quantum speed limit time (the minimal evolution time) for a qubit system interacting with a structural environment is investigated. We define a new bound for the quantum speed limits. It is shown that the non-Markovianity and the population of the excited state can fail to signal the quantum evolution acceleration, but the initial-state dependence is an important factor. In particular, we find that different quantum speed limits could produce contradictory predictions on the quantum evolution acceleration.

The multistability in the coupled semiconductor microcavities

We study the nonlinear phenomena of the coupled semiconductor microcavities driven by coherent lasers in different coupling regimes. It is shown that the bistability and multistability in the strong-coupling regime are gradually generated or eliminated by properly adjusting the coupling strength or the amplitude of the input pump laser. The proposed system serves as a good candidate for the diverse control optical switch and the potential applications.

Effects of the reservoir squeezing on the precision of parameter estimation

Abstract The effects of reservoir squeezing on the precision of parameter estimation are investigated analytically based on non-perturbation procedures. The exact analytic quantum Fisher information (QFI) is obtained. It is shown that the QFI depends on the estimated parameter and its decay could be reduced by the squeezed reservoir compared with thermal (vacuum) reservoir, in particular, if the squeezing phase matching is satisfied.

The Precision of Parameter Estimation for Dephasing Model Under Squeezed Reservoir

We study the precision of parameter estimation for dephasing model under squeezed environment. We analytically calculate the dephasing factor γ(t) and obtain the analytic quantum Fisher information (QFI) for the amplitude parameter α and the phase parameter ϕ. It is shown that the QFI for the amplitude parameter α is invariant in the whole process, while the QFI for the phase parameter ϕ strongly depends on the reservoir squeezing. It is shown that the QFI can be enhanced for appropriate squeeze parameters r and θ. Finally, we also investigate the effects of temperature on the QFI.

Analytic symmetric information-theoretical discord for one class of two-qubit states

We give the analytic expression for the information-theoretical symmetric discord of one type of two-qubit X states which depend on only four real parameters. As an application, we study the symmetric discord in a model, which shows that the numerical and analytic results are well consistent.

QUANTUM CORRELATIONS IN THE ENTANGLEMENT DISTILLATION PROTOCOLS

We study the quantum correlations between source and target pairs in different protocols of entanglement distillation of one kind of entangled states. We find that there does not exist any quantum correlation in the standard recurrence distillation protocol, while quantum discord and even quantum entanglement are always present in the other two cases of the improved distillation protocols. In the three cases, the distillation efficiency improved with the quantum correlations enhanced.