Narrow Results

In this paper we explore the design of microwave-based structures that can enhance the interaction of electromagnetic fields with cold-atom ensembles, leading to novel sensing modalities based on the quantum-mechanical behavior of these systems. In particular, we discuss electromagnetically-induced transparency in a single uncondensed cold-atom cloud, and a two-cloud version of a SQUID, where the clouds are BEC's and take the place of the weakly coupled superconductors. These systems are both promising candidates for use in the high-precision detection of chemical contaminants.

In this paper, electromagnetically-induced transparency (EIT) phenomena have been investigated numerically in the plasmonic waveguides composed of unsymmetrical slot shaped metal–insulator–metal (MIM) structures. By the transmission line theory and Fabry–Perot model, the formation and evolution mechanisms of plasmon-induced transparency were exactly analyzed. The analysis showed that the peak of EIT-like transmission could be changed easily according to certain rules by adjusting the geometrical parameters of the slot structures, including the coupling distances and slot depths. We can find a new method to design nanoscale optical switch, devices in optical storage and optical computing.

Graphene nanomaterials exhibit excellent optical properties when interacting with electromagnetical fields, which plays an important role in a wide range of applications such as optical communications, optical storage and other fields. Based on the electromagnetically induced transparency (EIT) effect, we investigate control of slow light in the Landau quantized graphene system with different three-level and four-level coupling schemes. Utilizing the EIT effect, group velocity of the probe fields can be significantly reduced and well controlled by manipulating Rabi frequencies and detunings of the coupling lasers as well as probe detuning. Furthermore, probe light with different frequencies can even be controlled in different EIT windows in the graphene system with the four-level scheme, which may find applications in signal selection and discrimination. This work can provide reference for the design of graphene-based quantum devices and have potential applications in optical communications and optical quantum information processing, etc.

A multi-functional terahertz metamaterial with electromagnetically induced transparency (EIT) and broadband absorptions is proposed. The unit cell of the metamaterial is comprised of an E shape and a split-ring resonator on the top of the polyimide. For TE and TM polarization, the temporal coupled-mode theory reveals that the EIT effect arises from coupling two resonators. The transparent windows are experimentally demonstrated at 0.205 THz and 0.44 THz for the TM and TE polarization, respectively. When the vanadium dioxide (${\text{VO}}_2)$ film is added to the bottom of the polyimide and works in the metallic state, the metamaterial could absorb electromagnetic waves in the broadband for the two polarizations, even in the case of oblique incidence. For the TE polarization, the relative bandwidth of the absorption over 60 % absorptance is 119.8 % in the range of 0.307 THz–1.225 THz. Meanwhile, for the TM polarization, the bandwidth over 60 % absorption is 68.8 % within the range of 0.52 THz–1.065 THz. The proposed multi-functional terahertz metamaterial can be widely used in sensing technology, optical storage, stealth technology, and other fields in reality.

In this paper, we have realized amplification without inversion (AWI) in quantum dot (QD). A Y-type four-level system of In_xGa_1-xN quantum dot has been obtained and investigated for AWI. It has been shown that, with proper setting of control fields' amplitude, we can obtain reasonable gain. With proper setting of phase difference of control fields and probe field, we can obtain considerable gain in resonant wavelength. We have designed this system by solving the Schrödinger–Poisson equations for In_xGa_1-xN quantum dot in GaN substrate, self-consistently.

We review recent experiments [M. D. Eisaman et al., Nature438 (2005) 837] demonstrating the generation of narrow-bandwidth single photons using a room-temperature ensemble of ⁸⁷Rb atoms. Our method involves creation of an atomic coherence via Raman scattering and projective measurement, followed by the coherent transfer of this atomic coherence onto a single photon using electromagnetically induced transparency (EIT). The single photons generated using this method are shown to have many properties necessary for quantum information protocols, such as narrow bandwidths, directional emission, and controllable pulse shapes. The narrow bandwidths of these single photons (~MHz), resulting from their matching to the EIT resonance (~MHz), allow them to be stored in narrow-bandwidth quantum memories. We demonstrate this by using dynamic EIT to store and retrieve the single photons in a second ensemble for storage times up to a few microseconds. We also describe recent improvements to the single-photon fidelity compared to the work by M. D. Eisaman in Nature438 (2005) 837. These techniques may prove useful in quantum information applications such as quantum repeaters, linear-optics quantum computation, and daytime free-space quantum communication.

In this paper we explore the design of microwave-based structures that can enhance the interaction of electromagnetic fields with cold-atom ensembles, leading to novel sensing modalities based on the quantum-mechanical behavior of these systems In particular, we discuss electromagnetically-induced transparency in a single uncondensed cold-atom cloud, and a two-cloud version of a SQUID, where the clouds are BEC's and take the place of the weakly coupled superconductors. These systems are both promising candidates for use in the high-precision detection of chemical contaminants.