Ultraslow Propagation of Entangled State via Four-Wave Mixing in a Coupled Double Quantum Well

An analytical method based on four-wave mixing （FWM） is here developed to study the generation of entangled state in an asymmetric semiconductor double quantum well structure. It is found that the maximally entangled state of two beams （the probe and four-wave mixing beams） can be achieved in an appropriate condition. Moreover, we also show that the two entangled beams propagate with ultraslow group velocity in the semiconductor medium. This investigation can be used for achieving the entangled beams in the semiconductor solid-state medium, which is much more practical than that in an atomic medium because of its flexible design and the wide adjustable parameters.     

Manipulation of Spontaneous Emission via Quantum Interference in an Elliptically Polarized Laser Field

Manipulation of spontaneous emission from an atom confined in three kinds of modified reservoirs has been investigated by means of an elliptically polarized laser field. Some interesting phenomena such as the multi-peak structure, extreme spectral narrowing, and cancellation of spontaneous emission can be observed by adjusting controllable system parameters. Moreover, these phenomena depend on the constructive or destructive quantum interference between multiple decay channels and which can be changed appreciably by varying the phase difference between the two circularly polarized components of the probe field. These results demonstrate the importance of an elliptically polarized laser field in controlling the spontaneous emission and its potential applications in high-precision spectroscopy.     

Control of Spontaneous Emission via a Single Elliptically Polarized Light in a Five-Level Atomic System

We investigate the features of the spontaneous emission spectra in a cold five-level atomic system coupled by a single elliptically polarized control field. We use wave function approach to derive the explicit and analytical expressions of atomic spontaneous emission spectra. It is shown that some interesting phenomena such as spectralline enhancement, spectral-line suppression, spectral-line narrowing, spectral-line splitting and dark fluorescence can be observed in the spectra by appropriately modulating the phase difference between the right-hand circularly (LHC) and left-hand circularly (RHC) polarized components of the elliptically polarized control field and the intensity of external magnetic field. The number of emission peaks, the positions of fluorescence-quenching points can be also controlled. Furthermore, we propose an ultracold 87Rb atomic system for experimental observation. These investigations may find applications in high-precision spectroscopy.