Atomic coherence

About: Atomic coherence is a research topic. Over the lifetime, 877 publications have been published within this topic receiving 29395 citations.

Coherent Photo-Association in Double-Well Bose Einstein Condensates

Abstract: We investigate the quantum dynamics and statistics of an interesting system of the double-well Bose–Einstein condensates in the presence of a coherent photo-association process occurring in one of the two wells. Through the analytical solutions of a simplified model of the atom–molecule condensate, our results show the important impact of initial state preparations on the atomic coherence, especially the different squeezing behaviour for the case of photo-association via left-well atoms tunnelling from initial right-well atomic condensate, which holds the promise to be observed in the present laboratory.

Phase-controlled electromagnetically induced focusing in a closed-loop atomic system

Abstract: In atomic systems, the spatially nonuniform distribution of a coupling field leads to the focusing of a probe beam producing a recipe for electromagnetically induced focusing (EIF). A diffraction-like pattern for the output probe beam can arise, and the probe radiation experiences focusing and defocusing across an electromagnetically induced transparency window. This phenomenon has critical implications for experiments on atomic coherence effects. Here, we study the EIF in a four-level closed-loop atomic system and show that full width at half-maximum (FWHM) of focused output probe intensity in the focal plane can be controlled by both intensity profile and relative phase of applied fields. We also demonstrate that the FWHM of the focused output probe intensity in focal length is much smaller than that of the input probe intensity, and in addition, through a special set of parameters, the minimum value of the FWHM can be obtained. Moreover, the FWHM can be made small by increasing Rabi frequency of the Gaussian signal field. Furthermore, the Gaussian probe intensity profile switches to a doughnut-like one just by changing the relative phase of applied fields. Finally, we apply a Laguerre–Gaussian signal field and find that the characteristics of the output probe field depend on the intensity profile of the signal field. Our results can be used to design a lens-like device with a controllable focal length and focusing strength that would pave the way toward all-optical switching devices.

Strong coupling of an optomechanical system to an anomalously dispersive atomic medium

Abstract: We investigate a hybrid optomechanical system in which a membrane oscillator is coupled to a collective spin of ground states of an intracavity $\Lambda$-type three-level atomic medium. The cavity field response is greatly modified by atomic coherence and the anomalous dispersion generated by two Raman pumping beams near two-photon resonance. The optomechanical interaction, therefore radiation pressure force, is substantially enhanced due to superluminal propagation of photons in the cavity. Such improvement facilitates ground-state cooling of the mechanical oscillator with room temperature thermal environment. Moreover, it can greatly improve the sensitivity and bandwidth of displacement measurement. In such system, optically-controlled strong-coupling interaction between the mechanical oscillator and cavity field could be implemented on small intracavity photon number, even at the single quanta level, which is important for weak-light nonlinear photonics and the generation of nonclassical quantum states in the mechanical field.

Quantum theory of electromagnetically induced suppression of absorption and inversionless lasing in a three-level system

Abstract: A full quantum treatment is given of suppression of absorption and lasing without inversion in a ∧-type three-level atom induced by a strong driving field resonant with the two lower levels. The nature of the quantum interference leading to the suppression of absorption and lasing without inversion and its relation to the initial state preparation are studied. Particular attention is given to the effects that arise specifically from the quantum nature of the driving field. It is shown that, because of the distinguishability of the states of the driving field that have different photon numbers, destructive interference is confined to occur within a finite region of the photon number space. A complete cancellation of absorption predicted in the semiclassical theory should thus be regarded as resulting from an ideal behavior achieved only in the classical limit when the driving field is given as a strong coherent field.