Direct Measurement of Light Speed Reduction in a Rubidium Vapour Medium Coherently Prepared by Electromagnetically Induced Transparency

We have experimentally observed the reduction of light speed in a rubidium vapour medium coherently preparedby electromagnetically induced transparency. The light speed reduction was deduced by directly measuring thetime delay of a probe light when it passed through the medium. The time delay varies with the intensity of thecoupling laser, and the typical time delay we recorded was 1.8 μs, corresponding to a light speed of 56000 m/s.     

Observation of Electromagnetically Induced Transparency by a Train of Short Pulses

We report the experimental demonstration of electromagnetically induced transparency in hot rubidium (^85Rb) atomic vapour by using an actively mode-locked external cavity diode laser in Littman-Metcalf configuration. We can make opaque resonant transitions transparent to any two optical comb components in the pulse trains which excite atomic coherence in the ground states of ^85Rb.     

Entropy and Entanglement of the Electromagnetically Induced Transparency System

We study the entropy and the entanglement of an electromagnetically induced transparency system. The quantumentanglement between the atom and the two quantized laser fields is discussed by using quantum reduced entropyand that between the two quantized laser fields by using quantum relative entropy. We also examine whetherinfluences of EIT on entropy and quantum entanglement of the system considered occur or not. Our resultsshow that the minimum value of the atomic reduced entropy may be regarded as an entropy criterion on theelectromagnetically induced transparency occurring.     

Generation of High-Dimensional Photon Entangled Coherent States in Double Electromagnetically Induced Transparency System

We present an approach to generate high-dimensional entangled coherent states between photons by using a dense atomic system in a double electromagnetically induced transparency state. The system under our consideration involves an atomic configuration with six internal states, two weak quantized probe lasers, and two strong classical coupling lasers. We show how to generate high dimensional entangled coherent states between the two probe lasers.     

Mixture of Electromagnetically Induced Transparency and Autler–Townes Splitting in a Five-Level Atomic System

Discerning electromagnetically induced transparency(EIT) from Autler–Townes splitting(ATS) is a significant issue in quantum optics and has attracted wide attention in various three-level configurations. Here we present a detailed study of EIT and ATS in a five-level atomic system considered to be composed of a four-level Y-type subsystem and a three-level Λ-type subsystem. In our theoretical calculations with standard density matrix formalism and steadystate approximation, we obtain the general analytical expression of the first-order matrix element responsible for the probe-field absorption. In light of the well-known three-level EIT and ATS criteria, we numerically show an intersection of EIT with ATS for the Y-type subsystem. Furthermore, we show that an EIT dip is sandwiched between two ATS dips(i.e., multi-dip mixture of EIT and ATS) in the absorption line for the five-level system, which can be explained by the dressed-state theory and Fano interference.     

Electromagnetically Induced Absorption and Transparency Spectra of Degenerate Two-Level Systems with a Strong Coupling Field in Cs Vapour

The electromagnetically induced absorption and electromagnetically induced transparency spectra of degenerate two-level systems with a strong coupling laser were observed. The frequency detuning and intensity effect of the coupling laser were demonstrated simultaneously. A dispersion-like spectrum can be obtained when the coupling laser is situated at blue-side detuning. The absorption inversion was realized when the coupling laser intensity is small. The coherent resonance has a linewidth much narrower than the natural linewidth of the optical transitions.     

Probe Amplification with or without Population Inversion in a Five-Level Atomic System with Double-Dark Resonances

We theoreticMly investigate the response of the probe amplification in a five-level atomlc system m the presence of interacting double-dark resonances disturbed by introducing an additional signal field. It is found that a large enhancement of the probe amplification with or without population inversion can be achieved by properly adjusting the strengths of the microwave driving field and the signal laser field. From viewpoint of physics, we qualitatively explain these results in terms of quantum interference and dressed states.