Geometric quantum gates robust against stochastic control errors

We analyze a scheme for quantum computation where quantum gates can be continuously changed from standard dynamic gates to purely geometric ones. These gates are enacted by controlling a set of parameters that are subject to unwanted stochastic fluctuations. This kind of noise results in a departure from the ideal case that can be quantified by a gate fidelity. We find that the maximum of this fidelity corresponds to quantum gates with a vanishing dynamical phase.Comment: 4 pager

Forward-Backward Multiplicity Correlations in Au+Au Collisions at sNN\sqrt{s_{NN}} = 200 Gev

The study of correlations among particles produced in different rapidity regions may provide understanding of the mechanisms of particle production. Correlations that extend over a longer range are observed in hadron-hadron interactions only at higher energies. Results for short and long-range multiplicity correlations (Forward-Backward) are presented for Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The growth of long range correlations are observed as a function of the pseudorapidity gap in central Au+Au collisions. The Dual Parton model and Color Glass Condensate phenomenology have been explored to understand the origin of long range correlations.Comment: 8 pages, 4 figures, IWCF06, Hangzhou, China, Nov. 21-24, 200

Technical Note: 30 years of HIRS data of upper tropospheric humidity

We use 30 years of intercalibrated HIRS (High-Resolution Infrared Radiation Sounder) data to produce a 30-year data set of upper tropospheric humidity with respect to ice (UTH_i). Since the required brightness temperatures (channels 12 and 6, <i>T</i>₁₂ and <i>T</i>₆) are intercalibrated to different versions of the HIRS sensors (HIRS/2 and HIRS/4) it is necessary to convert the channel 6 brightness temperatures which are intercalibrated to HIRS/4 into equivalent brightness temperatures intercalibrated to HIRS/2, which is achieved using a linear regression. Using the new regression coefficients we produce daily files of UTH_i, <i>T</i>₁₂ and <i>T</i>₆, for each NOAA satellite and METOP-A (Meteorological Operational Satellite Programme), which carry the HIRS instrument. From this we calculate daily and monthly means in 2.5° &times; 2.5° resolution for the northern midlatitude zone 30–60° N. As a first application we calculate decadal means of UTH_i and the brightness temperatures for the two decades 1980–1989 and 2000–2009. We find that the humidity mainly increased from the 1980s to the 2000s and that this increase is highly statistically significant in large regions of the considered midlatitude belt. The main reason for this result and its statistical significance is the corresponding increase of the <i>T</i>₁₂ variance. Changes of the mean brightness temperatures are less significant