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

Military Modernization and Peaceful Rising: A Harmonious Transition of the PLA into the Future

This article seeks to elucidate the recent changes to the Chinese military by examining the new characteristics of the People’s Liberation Army (PLA) and its newly adopted approaches for modernization between 2003 and 2008. It includes diachronic discussions to explore various social and political factors for the changes, domestic and international constraints on the implementation of military modernization, and the outcomes of these endeavors. The main findings indicate that the Chinese military has changed its main feature as two important transitions have emerged: first, the PLA has been transformed from a manpower intensive army to a technology oriented force; and second, from a national security army to an internationally operated force. Consequently, the high command begins to consider the PLA as a part of the global military cooperation

Analytical results for a parity-time symmetric two-level system under synchronous combined modulations

We propose a simple method of combined synchronous modulations to generate the analytically exact solutions for a parity-time symmetric two-level system. Such exact solutions are expressible in terms of simple elementary functions and helpful for illuminating some generalizations of appealing concepts originating in the Hermitian system. Some intriguing physical phenomena, such as stabilization of a non-Hermitian system by periodic driving, non-Hermitian analogs of coherent destruction of tunneling (CDT) and complete population inversion (CPI), are demonstrated analytically and confirmed numerically. In addition, by using these exact solutions we derive a pulse area theorem for such non-Hermitian CPI in the parity-time symmetric two-level system. Our results may provide an additional possibility for pulse manipulation and coherent control of the parity-time symmetric two-level system.Comment: 7 pages, 4 figure