Effects of depolarizing quantum channels on BB84 and SARG04 quantum cryptography protocols

We report experimental studies on the effect of the depolarizing quantum channel on weak-pulse BB84 and SARG04 quantum cryptography. The experimental results show that, in real world conditions in which channel depolarization cannot be ignored, BB84 should perform better than SARG04.Comment: 4 pages, 4 figure

Study of the Top-quark Pair Production in Association with a Bottom-quark Pair from Fast Simulations at the LHC

A large number of top quarks will be produced at the Large Hadron Collider (LHC) for Run II period. This will allow us to measure the rare processes from the top sector in great details. We present the study of the top-quark pair production in association with a bottom-quark pair (ttbb) from fast simulations for the Compact Muon Solenoid (CMS) experiment. The differential distributions of ttbb are compared with the top-quark pair production with two additional jets (ttjj) and with the production in association with the Higgs (ttH), where the Higgs decays to a bottom-quark pair. The significances of ttbb process in the dileptonic and semileptonic decay mode are calculated with the data corresponding to an integrated luminosity of 10 fb-1, which is foreseen to be collected in the early Run II period. This study will be an important input in searching for new physics beyond the standard model as well as in searching for ttH process where the Yukawa coupling with the top quark can be directly measured.Comment: 12 pages, 12 figure

Optimal Gaussian measurements for phase estimation in single-mode Gaussian metrology

The central issue in quantum parameter estimation is to find out the optimal measurement setup that leads to the ultimate lower bound of an estimation error. We address here a question of whether a Gaussian measurement scheme can achieve the ultimate bound for phase estimation in single-mode Gaussian metrology that exploits single-mode Gaussian probe states in a Gaussian environment. We identify three types of optimal Gaussian measurement setups yielding the maximal Fisher information depending on displacement, squeezing, and thermalization of the probe state. We show that the homodyne measurement attains the ultimate bound for both displaced thermal probe states and squeezed vacuum probe states, whereas for the other single-mode Gaussian probe states, the optimized Gaussian measurement cannot be the optimal setup, although they are sometimes nearly optimal. We then demonstrate that the measurement on the basis of the product quadrature operators XP+PX, i.e., a non-Gaussian measurement, is required to be fully optimal.Comment: 13 pages, 6 figure

Superparamagnetic Iron Oxide Nanoparticles Coated with Galactose-Carrying Polymer for Hepatocyte Targeting

Our goal is to develop the functionalized superparamagnetic iron oxide nanoparticles (SPIONs) demonstrating the capacities to be delivered in liver specifically and to be dispersed in physiological environment stably. For this purpose, SPIONs were coated with polyvinylbenzyl-O-β-D-galactopyranosyl-D-gluconamide (PVLA) having galactose moieties to be recognized by asialoglycoprotein receptors (ASGP-R) on hepatocytes. For use as a control, we also prepared SPIONs coordinated with 2-pyrrolidone. The sizes, size distribution, structure, and coating of the nanoparticles were characterized by transmission electron microscopy (TEM), electrophoretic light scattering spectrophotometer (ELS), X-ray diffractometer (XRD), and Fourier transform infrared (FT-IR), respectively. Intracellular uptake of the PVLA-coated SPIONs was visualized by confocal laser scanning microscopy, and their hepatocyte-specific delivery was also investigated through magnetic resonance (MR) images of rat liver. MRI experimental results indicated that the PVLA-coated SPIONs possess the more specific accumulation property in liver compared with control, which suggests their potential utility as liver-targeting MRI contrast agent

Moment-Fourier approach to ion parallel fluid closures and transport for a toroidally confined plasma

A general method of solving the drift kinetic equation is developed for an axisymmetric magnetic field. Expanding a distribution function in general moments a set of ordinary differential equations are obtained. Successively expanding the moments and magnetic-field involved quantities in Fourier series, a set of linear algebraic equations is obtained. The set of full (Maxwellian and non-Maxwellian) moment equations is solved to express the density, temperature, and flow velocity perturbations in terms of radial gradients of equilibrium pressure and temperature. Closure relations that connect parallel heat flux density and viscosity to the radial gradients and parallel gradients of temperature and flow velocity, are also obtained by solving the non-Maxwellian moment equations. The closure relations combined with the linearized fluid equations reproduce the same solution obtained directly from the full moment equations. The method can be generalized to derive closures and transport for an electron-ion plasma and a multi-ion plasma in a general magnetic field.Comment: 25 pages, 9 figure