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SGC Switching Between subluminal to Superluminal Propagation in V-Type Atom

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Communications in Theoretical Physics 2006年第4X期46卷 731-734页

作者： HAN Ding-An GUO Hong BAI Yan-Feng SUN Hui ZENG Ya-Guang CREAM Group Key Laboratory for Quantum Information and Measurements of Ministry of Education School of Electronics Engineering and Computer Science Peking University Beijing 100871 China Physics Department Foshan University Foshan 528000 China

For a V-type three-level atomic system with two closely spaced upper levels, we investigate the light pulse propagation properties with only one laser field. Due to spontaneously generated coherence, the group velocity of the light pulse can be changed from subluminal to superluminal. The effects of the field intensity and the two-upper level splitting on the group velocity are also shown. At last, an analytical expression for the group velocity is given in the case of a weak field.

关键词： spontaneously generated coherence superluminal subluminal

The manipulation of light pulse from subluminal to superluminal propagation in a degenerate two-level Cs atomic system

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Science China(Physics,Mechanics & Astronomy) 2014年第12期57卷 2246-2250页

作者： ZHANG Jun Xiang JIANG Qi Chang LIU Chao ZHANG Xin Sheng LIU Jin Hong The State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-Electronics Shanxi University

We experimentally demonstrate the propagation of light pulse from subluminal to superluminal light based on quantum coher- ence in a degenerate two-level atomic system in a Cs vapor cell. It is shown that the group velocity of light pulse can be switched from subluminal to superluminal propagation via changing the coupling field from a traveling wave to a standing wave, while can also be continuously manipulated by varying the intensity of two waves superposed to form a standing wave. The observed maximum delay and advance times are about 0.45 and 0.54 μs, corresponding to the group velocity of v8 = 168 km/s and ve =-138 krrt/s, respectively. This investigation may have the practical applications of devices for optical tunable delay lines, optical switching and optical buffering.

关键词： group velocity subluminal superluminal quantum coherence standing wave

SGC Switching Between subluminal to Superluminal Propagation in Ⅴ-Type Atom

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Communications in Theoretical Physics 2006年第10期 731-734页

作者： HAN Ding-An, GUO Hong,~1 BAI Yan-Feng,~1 SUN Hui,~1 and ZENG Ya-Guang~2 1 CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China 2 physics Department, Foshan University, Foshan 528000, China CREAM Group，Key Laboratory for Quantum Information and Measurements of Ministry of Education，School of Electronics Engineering and Computer Science，Peking University，Beijing 100871，China Physics Department，Foshan University，Foshan 528000，China CREAM Group，Key Laboratory for Quantum Information and Measurements of Ministry of Education，School of Electronics Engineering and Computer Science，Peking University，Beijing 100871，China Physics Department，Foshan University，Foshan 528000，China

关键词： spontaneously generated coherence superluminal subluminal

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subluminal Cosmology

Journal of Modern Physics 2017年第4期8卷 583-601页

作者： Rainer Burghardt Independent Researcher Obritz Austria

The standard model of cosmology is considered critically. A model with pressure is proposed which is linearly expanding and which is an exact solution of Einstein’s field equations. The recession velocity of the galaxies of this model never exceeds the speed of light. The model is closely related to the Rh=ct model of Melia, which is flat and infinite. However, our subluminal model is spatially positively curved and closed. Nevertheless all data from observations gathered and surveyed by Melia support our model.

关键词： Expanding Cosmos with Pressure subluminal Expansion Covariant Representation

Controlling group velocity in a superconductive quantum circuit

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Chinese Physics B 2012年第10期21卷 274-278页

作者：邱田会杨国建 Department of Physics and Applied Optics Beijing Area Major Laboratory Beijing Normal University

We investigate the controllable group velocity of a microwave probe field in a superconductive quantum circuit（SQC） pumped by microwave fields,and the use of such a SQC function as an artificial Λ-type three-level *** exchange between the subluminal and the superluminal states of the probe field can be realized simply by sweeping the pumping intensity,and the superluminal state is usually realized with a lower *** work is one of the efforts to extend the study of electromagnetically induced transparency and its related properties from the lightwave band to the microwave band.

关键词： subluminal superluminal superconductive quantum circuit group velocity

Sub- and Super-Luminal Phenomena in a Doubly Driven Four-Level System

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Communications in Theoretical Physics 2011年第4期55卷 671-675页

作者：韩定安曾亚光陈伟成董少光黄纯青朱传云梁佩莹 Department of Physics Foshan University

With the occurrence of an adding driving field, the properties of the dispersion and the absorption of a four-level system are changed greatly. The system can produce the normal and anomalous dispersion regions with proper parameters. Here, the driving fields can be seemed as knobs to manipulate the group velocity of a weak probe field between subluminal and superluminal.

关键词： group velocity subluminal superluminal driving fields

Influence of Doppler-broadening on absorption-dispersion properties in a resonant coherent medium

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Chinese Physics B 2005年第12期14卷 2496-2502页

作者：徐卫华高锦岳 Department of Physics College of Science Shenzhen University Shenzhen 518060 China Key Laboratory for Coherent Light Atomic and Molecular Spectroscopy of Education Ministry College of Physics Jilin University Changchun 130023 China

We investigate the influence of Doppler broadening on absorption-dispersion properties in a four-level atomic system that can evolve from a normal dispersion to an anomalous dispersion. Our results show that the absorption-dispersion properties become strongly dependent on the propagation directions of the applied fields if Doppler broadening is taken into account. Especially, the switchover in the sign of the dispersion is still achievable even in the presence of Doppler broadening if properly arranging the propagation directions of the applied fields, which is in contrast with the otherwise behaviours in some other configurations.

关键词： Doppler broadening absorption dispersion subluminal superluminal

Local and Global Flatness in Cosmology

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Journal of Modern Physics 2019年第12期10卷 1439-1453页

作者： Rainer Burghardt A-2061 Obritz 246 Obritz Austria

We raise the question of how the curvature parameter k is related to the curvature of the universe. We also show that, for a cosmological model that can be interpreted geometrically as a pseudo-hypersphere with a time-dependent radius, the Einstein field equations are not sufficient to fully describe the model. In addition, the differential equation system of Bianchi identities is required to describe the temporal evolution of the universe. We discuss the facts using the example of the de Sitter universe, the subluminal universe and the Rh=ct model by Melia. In particular, we discuss the formal differences between the two latter models and claim that both models are identical. We also examine the possibility of introducing non-comoving coordinates.

关键词： Curvature Parameter Bianchi Identities de Sitter Cosmos subluminal Cosmos Rh=ct Cosmos Geometric Horizon

Melia’s R<sub>h</sub>= ct Model Is by No Means Flat

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Journal of Modern Physics 2020年第5期11卷 703-711页

作者： Rainer Burghardt A-2061 Obritz 246 Obritz Austria

With the support of numerous arguments, it has been shown that Melia’s claim that his cosmological Rh = ct model is flat and infinite is erroneous. In contrast, the model is positively curved, closed and, therefore, ... 详细信息

关键词： Globally and Locally Flat Cosmos Melia’s Rh = ct Model subluminal Model Curvature Parameter