Ultra-Efficient Cooling of Resonators: Beating Sideband Cooling with Quantum Control

The present state-of-the-art in cooling mechanical resonators is a version of "sideband" cooling. Here we present a method that uses the same configuration as sideband cooling --- coupling the resonator to be cooled to a second microwave (or optical) auxiliary resonator --- but will cool significantly colder. This is achieved by varying the strength of the coupling between the two resonators over a time on the order of the period of the mechanical resonator. As part of our analysis, we also obtain a method for fast, high-fidelity quantum information-transfer between resonators.Comment: 4 pages, revtex4-1, 2 png figure

Any-order propagation of the nonlinear Schroedinger equation

We derive an exact propagation scheme for nonlinear Schroedinger equations. This scheme is entirely analogous to the propagation of linear Schroedinger equations. We accomplish this by defining a special operator whose algebraic properties ensure the correct propagation. As applications, we provide a simple proof of a recent conjecture regarding higher-order integrators for the Gross-Pitaevskii equation, extend it to multi-component equations, and to a new class of integrators.Comment: 10 pages, no figures, submitted to Phys. Rev.

Estimated Flood Discharges and Map of Flood-Inundated Areas for Omaha Creek, near Homer, Nebraska, 2005

Repeated flooding of Omaha Creek has caused damage in the Village of Homer. Long-term degradation and bridge scouring have changed substantially the channel characteristics of Omaha Creek. Flood-plain managers, planners, homeowners, and others rely on maps to identify areas at risk of being inundated. To identify areas at risk for inundation by a flood having a 1-percent annual probability, maps were created using topographic data and water-surface elevations resulting from hydrologic and hydraulic analyses. The hydrologic analysis for the Omaha Creek study area was performed using historical peak flows obtained from the U.S. Geological Survey streamflow gage (station number 06601000). Flood frequency and magnitude were estimated using the PEAKFQ Log-Pearson Type III analysis software. The U.S. Army Corps of Engineers’ Hydrologic Engineering Center River Analysis System, version 3.1.3, software was used to simulate the water-surface elevation for flood events. The calibrated model was used to compute streamflow-gage stages and inundation elevations for the discharges corresponding to floods of selected probabilities. Results of the hydrologic and hydraulic analyses indicated that flood inundation elevations are substantially lower than from a previous study

Quantum logic gates for coupled superconducting phase qubits

Based on a quantum analysis of two capacitively coupled current-biased Josephson junctions, we propose two fundamental two-qubit quantum logic gates. Each of these gates, when supplemented by single-qubit operations, is sufficient for universal quantum computation. Numerical solutions of the time-dependent Schroedinger equation demonstrate that these operations can be performed with good fidelity.Comment: 4 pages, 5 figures, revised for publicatio

Integração de bases de dados geográficos heterogêneas e distribuídas.

O alto custo da aquisição de dados geográficos aliado à complexidade das análises ambientais têm levado as comunidades de informação ao compartilhamento de dados existentes, armazenados por bases de dados de Sistemas de Informações Geográficas (SIG). Os mecanismos utilizados para proporcionar a troca de dados entre estas bases têm sido a conversão de formatos e o estabelecimento de padrões. Estas soluções são inadequadas, uma vez que requerem localizar os dados e compreender os formatos ou padrões envolvidos para estabelecer os processos de conversão e não garantem interoperabilidade, pois parte substancial da informação está contida nos procedimentos de consulta, manipulação e apresentação. Essa tese apresenta o Sistema MultiSIG que tem como proposta criar uma federação de dados aberta. Este Sistema objetiva proporcionar interoperabilidade semântica entre bases de dados geográficos heterogêneas e distribuídas sobre o ambiente da rede global Internet. O desenvolvimento deste Sistema contemplou as diferenças entre: i) os modelos de dados usados pelos SIG, ii) as linguagens de manipulação de dados oferecidas por estes sistemas, e iii) os esquemas decorrentes das diversas áreas de aplicação através de uma metodologia e de uma arquitetura, denominadas MultiSIG e MultiSIG, respectivamente. A MultiSIG estabelece as atividades necessárias para a integração de esquemas das bases de dados geográficos e a MultiSIG oferece um ambiente que proporciona a interoperabilidade entre estas bases. As principais contribuições decorrentes do desenvolvimento deste Sistema são: a proposta de um nível externo sobre o modelo de dados global, gerando um modelo de objetos para um esquema global externo. Este modelo de objetos fornece uma única percepção do significado dos dados armazenados pelas bases componentes da federação, mantendo suas características de temas e regiões; a metodologia MultiSIG para integração dos esquemas - contempla as diversas características envolvidas na construção de uma base de dados geográficos, de forma que um conjunto compartilhado de termos e definições utilizados pelas comunidades de informação seja definido e apresentado no esquema global; e a especificação da arquitetura MultiSIG para interoperabilidade: é especificado os serviços desta arquitetura, bem como serviços de suporte a outros trabalhos do Projeto WHIP (Workbench de Heterogeneidade, Interoperabilidade e Paralelismo). Deste modo, a arquitetura proposta oferece ferramentas para cadastrar o esquema, realizar consultas, solicitar apresentação de resultados e fornecer suporte à cooperação entre os administradores locais e global para a integração de esquemas. A metodologia e a arquitetura propostas foram avaliadas na integração de bases de dados voltadas para aplicações na área de hidrologia e ambiental. Os resultados desta implementação evidenciam que a interoperabilidade proporcionada pelo Sistema MultiSIG contribui como uma forma alternativa de acessar dados dispostos em outras bases de dados geográficos, preservando o investimento na informação geográfica armazenada pelas bases de dados. A estratégia adotada pelo Sistema MultiSIG se mostra eficiente, uma vez que não é necessário saber onde os dados estão localizados, além de promover maior sinergia entre as comunidades de informação.Tese (Doutorado em Engenharia de Sistemas e Computação) - Universidade Federal do Rio de Janeiro, Rio de Janeiro

Strong-field effects in the Rabi oscillations of the superconducting phase qubit

Rabi oscillations have been observed in many superconducting devices, and represent prototypical logic operations for quantum bits (qubits) in a quantum computer. We use a three-level multiphoton analysis to understand the behavior of the superconducting phase qubit (current-biased Josephson junction) at high microwave drive power. Analytical and numerical results for the ac Stark shift, single-photon Rabi frequency, and two-photon Rabi frequency are compared to measurements made on a dc SQUID phase qubit with Nb/AlOx/Nb tunnel junctions. Good agreement is found between theory and experiment.Comment: 4 pages, 4 figures, accepted for publication in IEEE Trans. Appl. Supercon

The sovereign yield curve and credit ratings in GIIPS

© 2020 International Review of Finance Ltd. 2020 This paper studies the impact of sovereign credit rating and outlook changes on the shape of the sovereign yield curve using data for five European countries, namely, Greece, Ireland, Italy, Portugal, and Spain, known as the GIIPS for the period of 2001–2016. We use the dynamic Nelson–Siegel model to estimate the level, slope, and curvature of the yield curve. Subsequently, we employ the vector autoregressive model to estimate the effect of sovereign rating and outlook changes on the sovereign yield curve. We find a significant effect of rating downgrades and an insignificant effect of rating upgrades in all five countries; however, the results for the effect of changes in outlook status are mixed. Our results remain robust to various sensitivity tests

Spectroscopy of Three-Particle Entanglement in a Macroscopic Superconducting Circuit

We study the quantum mechanical behavior of a macroscopic, three-body, superconducting circuit. Microwave spectroscopy on our system, a resonator coupling two large Josephson junctions, produced complex energy spectra well explained by quantum theory over a large frequency range. By tuning each junction separately into resonance with the resonator, we first observe strong coupling between each junction and the resonator. Bringing both junctions together into resonance with the resonator, we find spectroscopic evidence for entanglement between all three degrees of freedom and suggest a new method for controllable coupling of distant qubits, a key step toward quantum computation.Comment: 4 pages, 3 figure

Multilevel effects in the Rabi oscillations of a Josephson phase qubit

We present Rabi oscillation measurements of a Nb/AlOx/Nb dc superconducting quantum interference device (SQUID) phase qubit with a 100 um^2 area junction acquired over a range of microwave drive power and frequency detuning. Given the slightly anharmonic level structure of the device, several excited states play an important role in the qubit dynamics, particularly at high power. To investigate the effects of these levels, multiphoton Rabi oscillations were monitored by measuring the tunneling escape rate of the device to the voltage state, which is particularly sensitive to excited state population. We compare the observed oscillation frequencies with a simplified model constructed from the full phase qubit Hamiltonian and also compare time-dependent escape rate measurements with a more complete density-matrix simulation. Good quantitative agreement is found between the data and simulations, allowing us to identify a shift in resonance (analogous to the ac Stark effect), a suppression of the Rabi frequency, and leakage to the higher excited states.Comment: 14 pages, 9 figures; minor corrections, updated reference