arXiv subjects

Jianbing Qi

Publications and source records attributed to Jianbing Qi.

3 recordsLinked to original sources

arXiv2009

Electromagnetically induced transparency in an inverted Y-type four-level system

The interaction of a weak probe laser with an inverted-Y type four-level atomic system driven by two additional coherent fields is investigated theoretically. Under the influence of the coherent coupling fields, the steady-state linear susceptibility of the probe laser shows that the system can have single or double electromagnetically induced transparency windows depending on the amplitude and the detuning of the coupling lasers. The corresponding index of refraction associated with the group velocity of the probe laser can be controlled at both transparency windows by the coupling fields. The propagation of the probe field can be switched from superluminal near the resonance to subluminal on resonance within the single transparency window when two coupling lasers are on resonance. This provides a potential application in quantum information processing. We propose an atomic $^{87}Rb$ system for experimental observation.

quant-ph↗

arXiv2009

Control of spontaneous emission of an inverted Y-type atomic system coupled by three coherent fields

We investigate the spontaneous emission from an inverted Y-type atomic system coupled by three coherent fields. We use the Schrödinger equation to calculate the probability amplitudes of the wave function of the system and derive an analytical expression of the spontaneous emission spectrum to trace the origin of the spectral features. Quantum interference effects, such as the spectral line narrowing, spectrum splitting and dark resonance are observed. The number of spectral components, the spectral linewidth, and relative heights can be very different depending on the physical parameters. A variety of spontaneous emission spectral features can be controlled by the amplitudes of the coupling fields and the preparation of the initial quantum state of the atom. We propose an ultracold atomic $^{87}Rb$ system for experimental observation.

quant-ph↗

arXiv2005

Electromagnetically induced transparency and dark fluorescence in a cascade three-level Lithium molecule

We observed electromagnetically induced transparency (EIT) and dark fluorescence in a cascade three-level diatomic Lithium system using Optical-Optical Double Resonance (OODR) spectroscopy. When a strong coupling laser couples the intermediate state $A^{1}Σ^{+}_{u}(v=13, J=14)$ to the upper state $G^{1}Π_{g}(v=11, J=14)$ of $^7Li_2$, the fluorescence from both $A^{1}Σ^{+}_{u}$ and $G^{1}Π_{g}$ states was drastically reduced as the weak probe laser was tuned through the resonance transition between the ground state $X^{1}Σ^{+}_{g}(v=4, J=15)$ and the excited state $A^{1}Σ^{+}_{u}(v=13, J=14)$. The strong coupling laser makes an optically thick medium transparent for the probe transition. In addition, The fact that fluorescence from the upper state $G^{1}Π_{g}(v=11, J=14)$ was also dark when both lasers were tuned at resonance implies that the molecules were trapped in the ground state. We used density matrix methods to simulate the response of an open molecular three-level system to the action of a strong coupling field and a weak probe field. The analytical solutions were obtained under the steady-state condition. We have incorporated the magnetic sublevel (M) degeneracy of the rotational levels in the lineshape analysis and report $|M|$ dependent lineshape splitting. The theoretical calculations are in excellent agreement with the observed fluorescence spectra. We show that the coherence is remarkably preserved even when the coupling field was detuned far from the resonance.

quant-ph↗