Asymptotic analysis of silicon based Bragg fibers

We developed an asymptotic formalism that fully characterizes the propagation and loss properties of a Bragg fiber with finite cladding layers. The formalism is subsequently applied to miniature air-core Bragg fibers with Silicon-based cladding mirrors. The fiber performance is analyzed as a function of the Bragg cladding geometries, the core radius and the material absorption. The problems of fiber core deformation and other defects in Bragg fibers are also addressed using a finite-difference time-domain analysis and a Gaussian beam approximation, respectively

Revisiting the production of charmonium plus a light meson at PANDA

In this work, we calculate the total cross sections and the center-of-mass frame angular distributions of the charmonium production plus a light meson by the low energy $p\bar{p}$ interaction. The results of $p\bar{p}\to \pi^0 \Psi$ with and without form factor (FF) indicate that the FF contribution in the calculation cannot be ignored. The obtained cross section of $p\bar{p}\to \pi^0 J/\psi$ with FF can fit the E760 data well. We also predict the total cross sections and the center-of-mass frame angular distributions of $p\bar{p}\to \omega \Psi$, which show that these physical quantities are dependent on Pauli ($g_\omega$) and Dirac ($\kappa_\omega$) coupling constants of the $pp\omega$ interaction. Thus, $p\bar{p}\to \omega \Psi$ can be as the ideal channel to test the different theoretical values of $g_\omega$ and $\kappa_\omega$. Applying the formulae of $p\bar{p}\to \pi^0 \Psi$ and $p\bar{p}\to \omega \Psi$, we predict the total cross sections of the $p\bar{p}\to \eta \Psi$ and $p\bar{p}\to \rho \Psi$ reactions. Our results show a common behavior of the charmonium production with a light meson by the $p\bar{p}$ interaction, where the total cross section of the $\eta_c$ production is the largest one among all discussed processes. The above observations can be directly tested at the forthcoming $\bar{P}$ANDA experiment.Comment: 10 pages, 2 tables, 9 figures. Version published in Phys. Rev.

Modal analysis of Bragg onion resonators

From analysis of the high Q modes in a Bragg onion resonator with an omnidirectional reflector cladding, we establish a close analogy between such a resonator and a spherical hollow cavity in perfect metal. We demonstrate that onion resonators are ideal for applications that require a large spontaneous-emission factor ß, such as thresholdless lasers and single-photon devices

A scheme for tunable quantum phase gate and effective preparation of graph-state entanglement

A scheme is presented for realizing a quantum phase gate with three-level atoms, solid-state qubits--often called artificial atoms, or ions that share a quantum data bus such as a single mode field in cavity QED system or a collective vibrational state of trapped ions. In this scheme, the conditional phase shift is tunable and controllable via the total effective interaction time. Furthermore, we show that the method can be used for effective preparation of graph-state entanglement, which are important resources for quantum computation, quantum error correction, studies of multiparticle entanglement, fundamental tests of non-locality and decoherence.Comment: 7 pages, 5 figure

Functionalized Germanene as a Prototype of Large-Gap Two-Dimensional Topological Insulators

We propose new two-dimensional (2D) topological insulators (TIs) in functionalized germanenes (GeX, X=H, F, Cl, Br or I) using first-principles calculations. We find GeI is a 2D TI with a bulk gap of about 0.3 eV, while GeH, GeF, GeCl and GeBr can be transformed into TIs with sizeable gaps under achievable tensile strains. A unique mechanism is revealed to be responsible for large topologically-nontrivial gap obtained: owing to the functionalization, the $\sigma$ orbitals with stronger spin-orbit coupling (SOC) dominate the states around the Fermi level, instead of original $\pi$ orbitals with weaker SOC; thereinto, the coupling of the $p_{xy}$ orbitals of Ge and heavy halogens in forming the $\sigma$ orbitals also plays a key role in the further enlargement of the gaps in halogenated germanenes. Our results suggest a realistic possibility for the utilization of topological effects at room temperature

Time-reversal-invariant spin-orbit-coupled bilayer Bose-Einstein Condensates

Time-reversal invariance plays a crucial role for many exotic quantum phases, particularly for topologically nontrivial states, in spin-orbit coupled electronic systems. Recently realized spin-orbit coupled cold-atom systems, however, lack the time-reversal symmetry due to the inevitable presence of an effective transverse Zeeman field. We address this issue by analyzing a realistic scheme to preserve time-reversal symmetry in spin-orbit coupled ultracold atoms, with the use of Hermite-Gaussian-laser induced Raman transitions that preserve spin-layer time-reversal symmetry. We find that the system's quantum states form Kramers pairs, resulting in symmetry-protected gap closing of the lowest two bands at arbitrarily large Raman coupling. We also show that Bose gases in this setup exhibit interaction-induced layer-stripe and uniform phases as well as intriguing spin-layer symmetry and spin-layer correlation.Comment: 7 pages, 4 figure