Chunling Ding

High-precision atom localization via controllable spontaneous emission in a cycle-configuration atomic system

A scheme for realizing two-dimensional (2D) atom localization is proposed based on controllable spontaneous emission in a coherently driven cycle-configuration atomic system. As the spatial-position-dependent atom-field interaction, the frequency of the spontaneously emitted photon carries the information about the position of the atom. Therefore, by detecting the emitted photon one could obtain the position information available, and then we demonstrate high-precision and high-resolution 2D atom localization induced by the quantum interference between the multiple spontaneous decay channels. Moreover, we can achieve 100% probability of finding the atom at an expected position by choosing appropriate system parameters under certain conditions.

Classical theory of cylindrical nonlinear optics: Sum- and difference-frequency generation

The process of two input electromagnetic waves at different frequencies overlapping in a nonlinear medium is a typical phenomenon of nonlinear optics. The traditional method of dealing with such a problem is to use the coupled-wave equations. In this paper, sum- and difference-frequency generation of cylindrical electromagnetic waves in a nonlinear medium is investigated in a different way. We use exact solutions of Maxwells equations to describe the propagation of cylindrical electromagnetic waves in a nonlinear medium and show that sum- and difference-frequency generation comes out quite naturally from such exact solutions. For comparison, the traditional method of utilizing the coupled-wave equations is also discussed, and we find that the results obtained from the two different approaches are consistent with each other.

Polarization qubit phase gate between two far-infrared pulses in three-coupled quantum wells

The cross-Kerr nonlinearity arising between two far-infrared (FIR) pulses is investigated in a three-coupled-quantum-well (TCQW) structure based on intersubband transitions. The results show that the giant Kerr nonlinearity with a relatively large cross-phase-modulation phase shift can be used for realizing polarization quantum phase gate in this TCQW structure. Such a semiconductor system is much more practical than its atomic counterpart because of its flexible design and the wide tunable parameters. This protocol may have potential applications in FIR all-optical switch design and quantum information processing with solid-state materials.

Modification and control of the spontaneous emission from an M-type atom embedded in an anisotropic photonic crystal

We describe the spontaneous emission properties of an M-type five-level atom embedded in a photonic crystal (PC), which is coherently driven by two external laser fields. It leads to two types of quantum interference: reservoir-induced interference and laser-induced interference. Considering different detunings of atomic transition frequencies from band edges, we reveal some interesting phenomena such as spectral-line enhancement, spectral-line suppression, spectral-line narrowing, reservoir-induced cancellation of spontaneous emission and the appearance of dark lines, which originate from the quantum interference effects and the control of external laser fields. These investigations suggest possible applications in quantum optics, optical communications and in the fabrication of novel optoelectronic devices.

Trichromatic phase manipulation of optical high-order sidebands in a nanocavity coupled to a single quantum emitter

We explore the dependence of optical high-order sideband (HOS) spectra on the incident power and relative phase of a trichromatic driving field in a single-mode nanocavity coupled to a two-level quantum emitter beyond the weak excitation approximation. With state-of-the-art experimental system parameters, it is found that the generated HOS can be enhanced significantly, compared with the bichromatic excitation. By varying the powers and phases of the trichromatic components, a few interesting phenomena such as enhancement, suppression, and quenching of the HOS spectral lines can be achieved. For the phase dependence, it is the sum of relative phases of two sideband components of the trichromatic driving field to the central component that plays a crucial role in generating the HOS. Optical HOS spectra exhibit remarkably different features once the sum phase is changed, but are kept unchanged regardless of the respective phases when the sum phase is fixed. The influence of the other system parameters, including the emitter-cavity coupling strength and all kinds of relative frequency detunings, on optical HOS generation is also discussed in detail. The underlying physical mechanism for optical HOS generation is presented. This investigation may find applications in multimode quantum memories and information processing at a low pump power level using cavity quantum electrodynamics.

Extremely narrowed spontaneous emission spectrum induced by elliptically polarized light

Abstract We demonstrate the control of spontaneous emission from a five-level atom embedded in a modified reservoir under the action of a single control beam with elliptical polarization. For different initial-state preparations, we take into account the influence of the phase difference between the two circularly polarized components of the control beam on the behavior of spontaneous emission. For the ground initial states, the spontaneous emission spectrum usually shows ultranarrow central lines which are greatly enhanced. In contrast, for the excited initial states, these enhanced ultranarrow lines are significantly suppressed due to the destructive quantum interference. Furthermore, our numerical simulations indicate that the multipeak structure appears in the presence of the elliptically polarized control beam and external magnetic field. Such a scheme for controlling spontaneous emission may find applications in high-precision spectroscopy.