Coherent Destruction of Tunneling and Dark Floquet State

We study a system of three coherently coupled states, where one state is shifted periodically against the other two. We discover such a system possesses a dark Floquet state at zero quasienergy and always with negligible population at the intermediate state. This dark Floquet state manifests itself dynamically in terms of the suppression of inter-state tunneling, a phenomenon known as coherent destruction of tunneling. We suggest to call it dark coherent destruction of tunneling (DCDT). At high frequency limit for the periodic driving, this Floquet state reduces to the well-known dark state widely used for STIRAP. Our results can be generalized to systems with more states and can be verified with easily implemented experiments within current technologies.Comment: 5 pages, 3 figure

Nonlinear coherent destruction of tunneling

We study theoretically two coupled periodically-curved optical waveguides with Kerr nonlinearity. We find that the tunneling between the waveguides can be suppressed in a wide range of parameters due to nonlinearity. Such suppression of tunneling is different from the coherent destruction of tunneling in a linear medium, which occurs only at the isolated degeneracy point of the quasienergies. We call this novel suppression nonlinear coherent destruction of tunneling.Comment: 4 pages,5 figure

Quasi-energies and Floquet states of two weakly coupled Bose-Einstein condensates under periodic driving

We investigate the quasi-energies and Floquet states of two weakly coupled Bose-Einstein condensates driven by a periodic force. The quasi-energies and Floquet states of this system are computed within two different theoretical frameworks: the mean-field model and the second-quantized model. The mean-field approach reveals a triangular structure in the quasi-energy band. Our analysis of the corresponding Floquet states shows that this triangle signals the onset of a localization phenomenon, which can be regarded as a generalization of the well-known phenomenon called coherent destruction of tunneling. With the second quantized model, we find also a triangular structure in the quantum quasi-energy band, which is enveloped by the mean-field triangle. The close relation between these two sets of quasi-energies is further explored by a semi-classical method. With a Sommerfeld rule generalized to time-dependent systems, the quantum quasi-energies are computed by quantizing semiclassically the mean-field model and they are found to agree very well with the results obtained directly with the second-quantized model.Comment: 8pages,12figure

Occurrence and Control of Soybean Aphid, Aphis glycines Matsumura

The soybean aphid, Aphis glycines Matsumura, is one of the most important pests of soybean. The A. glycines outbreak in 1998 followed another aphid outbreak after 1989, which caused enormous economic losses. The aphid infested areas exceeded 200 thousand mu, and the soybean yields decreased by 20%. Among aphid infested areas, 78 thousand mu were severely infested with a yield loss of 46%. More than 3,000 mu had no yield at all.Originating text in Chinese.Citation: Wu, Xiaobing, Ni, Wenjun, Liu, Peijing. (1999). Occurrence and Control of Soybean Aphid, Aphis glycines Matsumura. How Peasants Can Increase Wealth, 6, 20

GA based adaptive singularity-robust path planning of space robot for on-orbit detection

As a new on-orbit detection platform, the space robot could ensure stable and reliable operation of spacecraft in complex space environments. The tracking accuracy of the space manipulator end-effector is crucial to the detection precision. In this paper, the Cartesian path planning method of velocity level inverse kinematics based on generalized Jacobian matrix (GJM) is proposed. The GJM will come across singularity issue in path planning, which leads to the infinite or incalculable joint velocity. To solve this issue, firstly, the singular value decomposition (SVD) is used for exposition of the singularity avoidance principle of the damped least squares (DLS) method. After that, the DLS method is improved by introducing an adaptive damping factor which changes with the singularity. Finally, in order to improve the tracking accuracy of the singularity-robust algorithm, the objective function is established, and two adaptive parameters are optimized by genetic algorithm (GA). The simulation of a 6-DOF free-floating space robot is carried out, and the results show that, compared with DLS method, the proposed method could improve the tracking accuracy of space manipulator end-effector