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In this paper we survey the geometric method in quantum control. By presenting a geometric representation of nonlocal two-qubit quantum operation, we show that the control of two-qubit quantum operations can be reduced to a steering problem in a tetrahedron. Two physical examples are given to illustrate this method. We also provide analytic approaches to construct universal quantum circuit from any arbitrary quantum gate. [ABSTRACT FROM AUTHOR]

Constructing a mathematic transfer function of pollen and climatic factors is one of the most important approaches in the quantitative reconstruction of paleoclimate elements. In the function building, the key point is the response sensitivity to the climate change for different pollen families and categories. As an example in this paper, the pollen samples from the surface and stratum in Dajiuhu basin, Shennongjia are used to estimate the sensitivity of pollen factor-temperature in the transfer function by the EOF analysis, multiple regression and stepwise regression techniques. Thereafter, the selection methods of pollen factors are discussed and compared with other results from different researchers. The results show that in the pollen samples, the quantity of woody plants is larger than others, but the woody plants have relatively lower sensitivity and slow responses to the climate evolution and abrupt climate change. While the pollens from lower grade plants (herb and fern) have a relatively high sensitivity to the temperature change and fast response to the abrupt climate changes. Therefore, the pollen of herb and fern may significantly record the extreme events in the climate change. Also in different regions, the pollen samples have different sensitivity and optimum combination in the transfer functions. Final conclusion is that the stepwise regression is one of the best methods for transfer function building since it can obtain the maximum multiple correlation coefficients and optimum combination of sensitive pollen factors. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to provide a brief review of some recent developments in quantum feedback networks and control. A quantum feedback network (QFN) is an interconnected system consisting of open quantum systems linked by free fields and/or direct physical couplings. Basic network constructs, including series connections as well as feedback loops, are discussed. The quantum feedback network theory provides a natural framework for analysis and design. Basic properties such as dissipation, stability, passivity and gain of open quantum systems are discussed. Control system design is also discussed, primarily in the context of open linear quantum stochastic systems. The issue of physical realizability is discussed, and explicit criteria for stability, positive real lemma, and bounded real lemma are presented. Finally for linear quantum systems, coherent H and LQG control are described. [ABSTRACT FROM AUTHOR]

Quantum measurement is a fundamental problem in quantum control theory and experiments. It can obtain unknown information of quantum systems, and can also change state of the systems inevitably. Both the outcome and back action could be used to control quantum systems. This paper presents recent research progress about optimal control of state transformation in finite-dimensional quantum systems by back action of non-selective quantum measurement, and optimal control of signal and background of CARS (coherent anti-Stokes Raman spectroscopy) by phase shaping technique. In measurement sequence control of finite-dimensional quantum systems, the necessary condition for critical points of the underlying state transformation objective is found to be a highly symmetric form as a chain of equalities, and analytical and numerical solutions in several cases are explored. In the CARS control, it is found that the maximal resonant signal and minimal background at a specific frequency can be achieved by shaping the probe pulse only while keeping pump and Stokes pulses in transform limited forms (TLFs). An arctan-type phase function is obtained for the probe pulse to simultaneously enhance the resonant signal and suppress the background. For broadband background elimination, we find that the optimal phase shaping scheme of probe pulse is quasi-time-delay while keeping the pump and Stokes pulses in TLFs. These conclusions could help design control strategies of quantum devices. [ABSTRACT FROM AUTHOR]

Climate change and hydrologic process response in the Tarim River Basin over the past 50 years are the tocus of more and more researchers' attention. In this paper, both temperature and precipitation time series were found to present a monotonic increasing trend using nonparametric tests. Noticeably, a significant step change in both temperature and precipitation time series occurred in 1986. By contrasting the trends of natural water process in headstream and mainstream, we found that it was anthropogenic activities not climate change that caused the river dried up and vegetation degenerated in the lower reaches of Tarim River. The results of gray correlation analysis show that the runoff of higher latitude distributing river is more closely associated with winter snow stocking, while that of lower latitude is more closely related to summer temperature. Runoff in the headstream is more sensitive to precipitation, while that in the mainstream is more sensitive to evaporation. The strong evaporation caused by increasing temperature weakened runoff to some extent in spite of the fact that precipitation increased over the past 50 years. [ABSTRACT FROM AUTHOR]

For quantum state trajectory tracking of density matrix in Liouville equation of quantum systems, with the help of concept in quantum system control, one can apply unitary transformation both to controlled system and free-evolutionary target system such as to change the time-variant and non-stationary target system into a stationary state. Therefore, the quantum state trajectory tracking problem becomes a steering one. State steering control law of the system transformed is designed by means of the Lyapunov stability theorem. Finally, numerical simulation experiments are given for a five-level energy quantum system. The comparison analysis of original system's trajectory tracking with other method illustrates the advantage in control time of the method proposed. [ABSTRACT FROM AUTHOR]

The past decade or two has witnessed tremendous progress in theory and practice of quantum control technologies. Bridging different scientific disciplines ranging from fundamental particle physics to nanotechnology, the goal of quantum control has been to develop effective and efficient tools for common analysis and design, but more importantly would pave the way for future technological applications. This article briefly reviews basic quantum control theory from the perspective of modeling, analysis and design, as well as considers future research directions. [ABSTRACT FROM AUTHOR]

Because of the sensitivity of the Kalman framework to gross errors, proper techniques for detection of gross errors are necessary. By integrating the selection of quasi-accurate observations and the Kalman framework, a new filter called the quasi-accurate filter (QUAF) is developed. The expansibility and implementation scheme of the new algorithm are then discussed in detail, and the reliability matrix for the Kalman filter is proposed to analyze the reliability of the filters with different detection technologies. Finally, the experimental results from a real world case study are used to validate the conclusions. The QUAF carries out the preliminary selection of the quasi-accurate observations (QAOs) using the innovation of the Kalman filter, and use the check QAOs to determine reasonable observations. This causes the QUAF to handle more easily and possess wider expansibility. QUAF can be reformulated to the special cases of several common detection methods, such as the innovation method, robust estimation and quasi-accurate detection (QUAD). Since only reasonable observations are used, the QUAF has better detection accuracy and stronger avoidance of gross errors than the innovation method and robust estimation. Meanwhile, compared with QUAD methods, QUAF introduces the state-predicted model, requiring fewer quasi-accurate observations and making it more suitable for systems with complicated observation structures or sparse observations. [ABSTRACT FROM AUTHOR]

The identified results of 121 surface sediment spore-pollen samples in Shennongjia and meteorological data base of 30 years (January, 1971-December, 2000) of 7 meteorological stations around Dajiuhu, Shennongjia are used in this study. Selecting 55 species of common spore-pollen with the method of space fitting and stepwise regression we construct the pollen climate factor transfer function of annual mean temperature: T= 7.649 - 2.33097XAbles-0.10873XBetula-0.17352XCompositae-0.131 76XCruciterae + 0.13356XEuphorbiaceae-0.83069XCampanuiaceae + 1.96494XPyrrosia + 0.38411 XPteris + 2.77741 XSelaginetta + 0.04439XMonoIites. We had reconstructed annual mean temperature series by use of the sporo-pollen samples concentration percentage in peat section with 297 cm thickness in Dajiuhu since 15.753 kaBP. The temperature series reflect well the character of climatic change since the late glacial, which indicates extreme cold climate event of the Oldest Dryas, the Older Dryas, the Younger Dryas and the 8.2 kaBP, the same to the climate fluctuations of Boiling Warm Period and Allerod Warm Period, and the character of temperature change fluctuating frequently at the transition age from the late glacial to the Holocene. The reconstructed temperature also indicate Holocene Optimum, late Holocene warm-dry climate, and the character of climatic change in Dajiuhu in the last 1 ka. The conclusion is that the sporo-pollen samples have important climatic significance to surface sediment and the section of Dajiuhu, Shennongjia and important reference value to studying climatic change during the last glaciation by the temperature transfer function and reconstructed temperature series. [ABSTRACT FROM AUTHOR]

Focuses on a study which utilized the self-stable region (SSR) approach to investigate the extended state observer (ESO) design and its stability analysis. Advantages of the non-smooth structure in ESO; Convergence of ESO with the use of the SSR method; Estimation precision of non-smooth continuous extended state observer.