A large-scale one-way quantum computer in an array of coupled cavities

We propose an efficient method to realize a large-scale one-way quantum computer in a two-dimensional (2D) array of coupled cavities, based on coherent displacements of an arbitrary state of cavity fields in a closed phase space. Due to the nontrivial geometric phase shifts accumulating only between the qubits in nearest-neighbor cavities, a large-scale 2D cluster state can be created within a short time. We discuss the feasibility of our method for scale solid-state quantum computationComment: 5 pages, 3 figure

Remark on approximation in the calculation of the primordial spectrum generated during inflation

We re-examine approximations in the analytical calculation of the primordial spectrum of cosmological perturbation produced during inflation. Taking two inflation models (chaotic inflation and natural inflation) as examples, we numerically verify the accuracy of these approximations.Comment: 10 pages, 6 figures, to appear in PR

Twisted and Nontwisted Bifurcations Induced by Diffusion

We discuss a diffusively perturbed predator-prey system. Freedman and Wolkowicz showed that the corresponding ODE can have a periodic solution that bifurcates from a homoclinic loop. When the diffusion coefficients are large, this solution represents a stable, spatially homogeneous time-periodic solution of the PDE. We show that when the diffusion coefficients become small, the spatially homogeneous periodic solution becomes unstable and bifurcates into spatially nonhomogeneous periodic solutions. The nature of the bifurcation is determined by the twistedness of an equilibrium/homoclinic bifurcation that occurs as the diffusion coefficients decrease. In the nontwisted case two spatially nonhomogeneous simple periodic solutions of equal period are generated, while in the twisted case a unique spatially nonhomogeneous double periodic solution is generated through period-doubling. Key Words: Reaction-diffusion equations; predator-prey systems; homoclinic bifurcations; periodic solutions.Comment: 42 pages in a tar.gz file. Use ``latex2e twisted.tex'' on the tex files. Hard copy of figures available on request from [email protected]

Non-Thermal Production of WIMPs and the Sub-Galactic Structure of the Universe

There is increasing evidence that conventional cold dark matter (CDM) models lead to conflicts between observations and numerical simulations of dark matter halos on sub-galactic scales. Spergel and Steinhardt showed that if the CDM is strongly self-interacting, then the conflicts disappear. However, the assumption of strong self-interaction would rule out the favored candidates for CDM, namely weakly interacting massive particles (WIMPs), such as the neutralino. In this paper we propose a mechanism of non-thermal production of WIMPs and study its implications on the power spectrum. We find that the non-vanishing velocity of the WIMPs suppresses the power spectrum on small scales compared to what it obtained in the conventional CDM model. Our results show that, in this context, WIMPs as candidates for dark matter can work well both on large scales and on sub-galactic scales.Comment: 6 pages, 2 figures; typo corrected; to appear in PR

Superconducting properties of ultrathin Bi2Sr2CaCu2O8+x single crystals

We use Ar-ion milling to thin Bi2212 single crystals down to a few nanometers or one-to-two (CuO2)2 layers. With decreasing the thickness, superconducting transition temperature gradually decreases to zero and the in-plane resistivity increases to large values indicating the existence of a superconductor-insulator transition in ultrathin Bi2212 single crystals.Comment: 17 pages, 6 figures, to appear in J. Appl. Phys. 98(3) 200

Gaseous pollutants in Beijing urban area during the heating period 2007–2008: variability, sources, meteorological, and chemical impacts

Gaseous pollutants, NO<sub>y</sub>/NO<sub>x</sub>, SO<sub>2</sub>, CO, and O<sub>3</sub>, were measured at an urban site in Beijing from 17 November 2007 to 15 March 2008. The average concentrations (with ± 1σ) of NO, NO<sub>2</sub>, NO<sub>x</sub>, NO<sub>y</sub>, CO, SO<sub>2</sub>, and O<sub>3</sub> were 29.0 ± 2.7 ppb, 33.7 ± 1.4 ppb, 62.7 ± 4.0 ppb, 72.8 ± 4.5 ppb, 1.99 ± 0.13 ppm, 31.9 ± 2.0 ppb, and 11.9 ± 0.8 ppb, respectively, with hourly maxima of 200.7 ppb, 113.5 ppb, 303.9 ppb, 323.2 ppb, 15.06 ppm, 147.3 ppb, and 69.7 ppb, respectively. The concentrations of the pollutants show "saw-toothed" patterns, which are attributable mainly to changes in wind direction and speed. The frequency distributions of the hourly mean concentrations of NO<sub>y</sub>, SO<sub>2</sub>, CO, and O<sub>3</sub> can all be decomposed in the two Lorentz curves, with their peak concentrations representing background levels under different conditions. During the observation period, the average ratio NO<sub>x</sub>/NO<sub>y</sub> was 0.86 ± 0.10, suggesting that the gaseous pollutants in Beijing in winter are mainly from local emissions. Data of O<sub>3</sub>, NO<sub>z</sub>, and NO<sub>x</sub>/NO<sub>y</sub> indicate that photochemistry can take place in Beijing even in the cold winter period. Based on the measurements of O<sub>3</sub>, NO<sub>x</sub>, and NO<sub>y</sub>, ozone production efficiency (OPE) is estimated to be in the range of 0–8.9 (ppb ppb<sup>−1</sup>) with the mean(± 1σ) and median values being 1.1(± 1.6) and 0.5 (ppb ppb<sup>−1</sup>), respectively, for the winter 2007–2008 in Beijing. This low OPE would cause a photochemical O<sub>3</sub> source of 5 ppb day<sup>−1</sup>, which is small but significant for surface O<sub>3</sub> in winter in Beijing. Downward transport of O<sub>3</sub>-rich air from the free troposphere is the more important factor for the enhancement of the O<sub>3</sub> level in the surface layer, while high NO level for the destruction of O<sub>3</sub>. The concentrations of SO<sub>2</sub>, CO, and NO<sub>x</sub> are strongly correlated among each other, indicating that they are emitted by some common sources. Multiple linear regression analysis is applied to the concentrations of NO<sub>y</sub>, SO<sub>2</sub>, and CO and empirical equations are obtained for the NO<sub>y</sub> concentration. Based the equations, the relative contributions from mobile and point sources to NO<sub>y</sub> is estimated to be 66 ± 30 % and 40 ± 16 %, respectively, suggesting that even in the heating period, mobile sources in Beijing contribute more to NO<sub>y</sub> than point sources

A single intrinsic Josephson junction with double-sided fabrication technique

We make stacks of intrinsic Josephson junctions (IJJs) imbedded in the bulk of very thin ($d\leq 100$~nm) $\mathrm{Bi_2Sr_2CaCu_2O_{8+x}}$ single crystals. By precisely controlling the etching depth during the double-sided fabrication process, the stacks can be reproducibly tailor-made to be of any microscopic height ($0-9 \mathrm{nm} <d$), i.e. enclosing a specified number of IJJ (0-6), including the important case of a single junction. We discuss reproducible gap-like features in the current-voltage characteristics of the samples at high bias.Comment: 3 pages, 4 figures, to be published in APL May. 2

Multi-spectral window radiance observations of Cirrus from satellite and aircraft, November 2, 1986 Project FIRE

High resolution infrared radiance spectra achieved from the NASA ER2 airborne HIS experiment are used to analyze the spectral emissivity properties of cirrus clouds within the 8 to 12 micron atmospheric window region. Observations show that the cirrus emissivity generally decreases with increasing wavenumber (i.e., decreasing wavelength) within this band. A very abrupt decrease in emissivity (increase in brightness temperature) exists between 930/cm (10.8 microns) and 1000/cm (10.0 microns), the magnitude of the change being associated with the cirrus optical thickness as observed by lidar. The HIS observations are consistent with theoretical calculations of the spectral absorption coefficient for ice. The HIS observations imply that cirrus clouds can be detected unambiguously from the difference in brightness temperatures observed within the 8.2 and 11.0 micron window regions of the HIRS sounding radiometer flying on the operational NOAA satellites. This ability is demonstrated using simultaneous 25 km resolution HIRS observations and 1 km resolution AVHRR imagery achieved from the NOAA-9 satellite. Finally, the cirrus cloud location estimates combined with the 6.7 micron channel moisture imagery portray the boundaries of the ice/vapor phase of the upper troposphere moisture. This phase distinction is crucial for infrared radiative transfer considerations for weather and climate models, since upper tropospheric water vapor has little effect on the Earth's outgoing radiation whereas cirrus clouds have a very large attenuating effect

Effect of inter-subsystem couplings on the evolution of composite systems

The effect of inter-subsystem coupling on the adiabaticity of composite systems and that of its subsystems is investigated. Similar to the adiabatic evolution defined for pure states, non-transitional evolution for mixed states is introduced; conditions for the non-transitional evolution are derived and discussed. An example that describes two coupled qubits is presented to detail the general presentation. The effects due to non-adiabatic evolution on the geometric phase are also presented and discussed.Comment: 5 pages, 1 figur