Coherent manipulation of quantum states in a coupled cavity-atom system

We study atomic coherence and interference in four-level atoms confined in an optical cavity and explores the interplay between cavity QED and electromagnetically induced transparency (EIT). The destructive interference can be induced in the coupled cavityatom system with a free-space control laser tuned to the normal mode resonance and leads to suppression of the normal mode excitation. Then by adding a pump laser coupled to the four-level atoms from free space, the control-laser induced destructive interference can be reversed and the normal mode excitation is restored. When the free-space control laser is tuned to the atomic resonance and forms a Λ-type EIT configuration with the cavity-atom system, EIT is manifested as a narrow transmission peak of a weak probe laser coupled into the cavity mode. With the free-space pump laser driving the cavity-confined atoms in a four-level configuration, the narrow transmission peak of the cavity EIT can be split into two peaks and the dressed intra-cavity dark states are created analogous to the dressed states in free space. We report experimental studies of such coherently coupled cavityatom system realized with cold Rb atoms confined in an optical cavity and discuss possible applications in quantum nonlinear optics and quantum information science

Study on ecological quality evaluation of mining area based on remote sensing green index—Taking Yima mining area as an example

Mining and development of mining area poses significant impact on regional ecological quality. This study proposed a new remote sensing green index(RSGI)model more tailored for evaluating the ecological quality in the mining area by taking the Yima mining area as an example for analysis. The model was first applied to the ecological quality evaluation of the Yima mining area. Based on Landsat remote sensing images in 1991, 2011 and 2021, ENVI5.3 software was used to supervise the classification of remote sensing images and calculate the green index of remote sensing. The ecological quality of Yima Mining area in the past 30 years was evaluated from the perspective of time and space. Pearson correlation coefficient is used to analyze the correlation between ecological quality and ecological factors in mining area. Results showed that: ① From 1991 to 2021, the overall ecological quality was satisfactory, with the green space area reached more than 80 %. ② In 1991, 2011 and 2021, the RSGI values of Yima mining area were 0.90, 0.91 and 0.89, respectively. The ecological quality of Yima mining area showed initial increase and then a slow decline, and the overall ecological quality exhibits in a downward trend. ③ From 1991 to 2021, there were significant changes of eco-quality in towns and mining areas, with a downward trend observed in most regions. This indicates that the changes of eco-quality in Yima mining area is closely related to mining activities. ④ Areas with high remote sensing green index demonstrate larger proportion of cultivated land, forest land and grassland, and smaller proportion of buildings and impervious surface area. There is a significant correlation between remote sensing green index and other indexes. The research results provide reference for eco-environmental restoration and green mine construction in Yima mining area

Climate Change Contribution to Forest Growth in Eastern China over Past Two Decades

China has experienced substantial climate change during past decades. To understand the response of forests to this change, we investigated the trends in forest growth and the control mechanism behind the observed variations in the North-South Transect of Eastern China (NSTEC). Interpretations were made based on the Normalized Difference Vegetation Index (NDVI) and temperature and precipitation data from 1982 to 2006. Our results indicated that the growing season NDVI trend showed a significant linear relationship with the mean growing season temperature and precipitation trend exhibiting inconsistent or even opposite performances from the north to south of the NSTEC. Prevalent forest greening was observed in the cold and dry regions where the climate becomes warmer and drier, while forest browning appeared to dominate in the warm and humid areas where climate turns warmer and wetter. These phenomena indicated the positive effect of growing season climates on forest growth may stall under warmer and wetter conditions in the much warmer and wetter regions. Our findings showed a difference in growth trend between needle leaf forests and broadleaf forests. In the cold and dry regions, the NDVI of most needle leaf forests showed an increasing trend, but nearly half of the broadleaf forests exhibited a negative NDVI slope while the other broadleaf forests exhibited a positive NDVI slope