Application of a simplified probe feed impedance formula to the design of a dual frequency patch antenna

A simplified probe feed input impedance for a rectangular patch antenna based on the Green's function is used to design a dual frequency matched antenna. The predicted results at design frequencies of 1.9 and 2.4 GHz are in close agreement with experimental measurements

The ping-pong protocol can be attacked without eavesdropping

Attack the ping-pong protocol without eavesdropping.Comment: PACS: 03.67.H

Monte Carlo Hamiltonian

We suggest how to construct an effective low energy Hamiltonian via Monte Carlo starting from a given action. We test it by computing thermodynamical observables like average energy and specific heat for simple quantum systems.Comment: Contribution to Lattice'99 (Theoretical developments) Text (LaTeX file) + 2 figures (ps files

Nonlocal noise cross-correlation mediated by entangled Majorana fermions

Due to their nonlocality, qubits nested in Majorana bound states may be the key to realize decoherence-free quantum computation. Majorana bound states could be achieved at the ends of a one-dimensional topological superconductor. However, when the bound states couple directly to electron reservoirs their nonlocal correlation is quenched by local Andreev reflections. Here we propose a scheme to generate nonlocal noise cross correlation between two well-separated quantum dots, mediated by a pair of Majorana bound states. Both positive and negative cross correlations can be obtained by tuning the gate voltages applied to the dots. Within a limited range of finite temperatures, the cross correlation is not suppressed by thermal fluctuations. Furthermore, we show how the local Andreev reflections suppress the noise cross correlation when multiple dot energy levels are coupled to the Majorana bound states. The measurable cross correlation is expected to serve as a sensitive indicator for the generation of Majorana fermions.Comment: 8 pages, 5 figure

Superconductivity in Tetragonal LaPt_{2-x}Ge_{2+x}

We find that a tetragonal CaBe_2Ge_2-type structure can be stabilized in non-stoichiometric LaPt_{2-x}Ge_{2+x}. We further discovered that tetragonal LaPt_{2-x}Ge_{2+x} with x=0.15 and 0.2 respectively superconduct at Tc=1.85 K and 1.95 K, which is about four time higher than that in monoclinic LaPt_2Ge_2.Comment: 6 pages, 4 figure