Yang Ya-Ping

Quantum Entropy Controlling in the Damping Jaynes–Cummings Model

The quantum entropy of the damping Jaynes–Cummings model is investigated in different decay coefficients under detuning conditions. The results indicate that the larger the decay coefficient is, the more quickly the entropy decays. The detuning of the atom and field frequencies reduce the entanglement maximum in short time regions, but delays the damping process of the entanglement. The sine modulation enhances the entanglement in short time regions.

Repulsive and Restoring Casimir Forces Based on Magneto-Optical Effect

The Casimir force direction tuned by the external magnetic field due to the magneto-optical Voigt effect is investigated. The magneto-optical effect gives rise to the modified frequency-dependent electric permittivity and thus the electromagnetic properties of the materials can be adjusted to satisfy the condition of the formation of repulsive Casimir force. It is found that between the ordinary dielectric slab and magneto-optical material slab, a repulsive force may exist by adjusting the applied magnetic field. The restoring Casimir force can also be obtained if suitable parameter values are taken. For realistic materials, the repulsive and the restoring force is shown to possibly take place at typical distances in microelectromechanical systems.

Controlling nonclassical properties of the two-photon process by a time-varying field

The interactions between a two-level atom and a field via two-photon transition without rotating wave approximation have been investigated. We emphasize the dynamic behaviors of the atomic population inversion, the field squeezing, and the atomic dipole squeezing numerically when the field frequency varies with time in the forms of sine and rectangle. Some interesting phenomena are discovered and discussed. The good periodic character of the atomic population inversion in the standard two-photon Jaynes?Cummings model is weakened by the influence of the sine field frequency modulation. The rectangular field frequency modulation can change the correlation among different oscillations suddenly and induce new collapse-revival processes of the atomic population inversion. The field squeezing increases at the beginning of time, but then decreases and loses as the time increases after it reaches the maximum due to the sine modulation. The effects of the rectangular modulation on the field squeezing depend mostly on the appearance time of the modulation. The atomic dipole squeezing is weakened under the influence of the sine or rectangular modulation. Our results indicate that it is possible to perform the dynamic controlling of the system properties by changing the parameters of the system with time. This implies that one can dynamically control a quantum information process by choosing the system modulation properly.

Evolution of Population Inversion Controlled by the Time-Dependent Coupling: an Inverse Problem

We propose an inverse idea of controlling the evolution of the population inversion by a time-dependent coupling between the cavity field and a two-level system described through the Jaynes–Cummings model. We demonstrate the detailed procedure by obtaining the population evolution taking the non-sinusoidal form, which is different from the previous sinusoidal Rabi oscillation as the cavity field frequency and coupling parameters are constant during the interaction time.

An Effective Three-Dimensional Micromagnetic Method and Its Application to Magnetic Tunnel Junctions

An effective three-dimensional micromagnetic method for predicting equilibrium configuration of magnetization states is presented with conjugate-gradient technique to minimize the total energy, which has a much faster convergence rate than that of the quasi-Newton method. As an application, magnetic tunnel junctions with pinholes in the ultrathin barrier are simulated. The calculated coupling field Hf increases with the pinhole density increase, corresponding to the decrease of barrier thickness. The free layer domain configuration of tunnel junction during the switching process is also demonstrated.

A Method of Determining Representation of Quonic Algebra

In this letter, we construct representation of quonic algebra in quite a different method compared with the conventional one.

On q-Commutator in the Case q3+1 = 1

In this letter, the representations of q-Commutator in the Case q3+1 = 1 and the eigenstates of annihilation operator have been discussed.

On q-Defomed Creation Operator a†

In this paper, we construct the eigenstate of q-deformed creation operator a† by using the contour integral representation of δ function. Some of its properties are presented.