QND measurement of a superconducting qubit in the weakly projective regime

Quantum state detectors based on switching of hysteretic Josephson junctions biased close to their critical current are simple to use but have strong back-action. We show that the back-action of a DC-switching detector can be considerably reduced by limiting the switching voltage and using a fast cryogenic amplifier, such that a single readout can be completed within 25 ns at a repetition rate of 1 MHz without loss of contrast. Based on a sequence of two successive readouts we show that the measurement has a clear quantum non-demolition character, with a QND fidelity of 75 %.Comment: submitted to PR

Interqubit coupling mediated by a high-excitation-energy quantum object

We consider a system composed of two qubits and a high-excitation-energy quantum object used to mediate coupling between the qubits. We treat the entire system quantum mechanically and analyze the properties of the eigenvalues and eigenstates of the total Hamiltonian. After reproducing well-known results concerning the leading term in the mediated coupling, we obtain an expression for the residual coupling between the qubits in the off state. We also analyze the entanglement between the three objects, i.e. the two qubits and the coupler, in the eigenstates of the total Hamiltonian. Although we focus on the application of our results to the recently realized parametric-coupling scheme with two qubits, we also discuss extensions of our results to harmonic-oscillator couplers, couplers that are near resonance with the qubits and multi-qubit systems. In particular, we find that certain errors that are absent for a two-qubit system arise when dealing with multi-qubit systems.Comment: 15 pages (two-column

Role of relaxation in the quantum measurement of a superconducting qubit using a nonlinear oscillator

We analyze the relaxation of a superconducting flux qubit during measurement. The qubit state is measured with a nonlinear oscillator driven across the threshold of bifurcation, acting as a switching dispersive detector. This readout scheme is of quantum non-demolition type. Two successive readouts are used to analyze the evolution of the qubit and the detector during the measurement. We introduce a simple transition rate model to characterize the qubit relaxation and the detector switching process. Corrected for qubit relaxation the readout fidelity is at least 95%. Qubit relaxation strongly depends on the driving strength and the state of the oscillator.Comment: 4 pages, 4 figure

Effect of a 6-month brisk walking program on walking endurance in sedentary and physically deconditioned women aged 60 or older: A randomized trial

International audienceBACKGROUND:Walking endurance is a predictor of healthy ageing.OBJECTIVE:To examine if a 6-month brisk walking program can increase walking endurance in sedentary and physically deconditioned older women.TRIAL DESIGN:Randomized controlled trial.SETTING:Women recruited from public meetings aimed at promoting physical activity in women aged 60 or older.SUBJECTS:121 women aged 65.7 ± 4.3 years, with sedentary lifestyle (Physical Activity Questionnaire for the Elderly score 46%) were those with baseline lowest values of 6MWD (p=0.001) and highest values of body mass index (BMI) (p<0.01).CONCLUSION:Present results support recommendation that brisk walking programs should be encouraged to improve walking endurance in physically deconditioned women aged 60 or older, especially in those with high BMI

Social Interactions vs Revisions, What is important for Promotion in Wikipedia?

In epistemic community, people are said to be selected on their knowledge contribution to the project (articles, codes, etc.) However, the socialization process is an important factor for inclusion, sustainability as a contributor, and promotion. Finally, what does matter to be promoted? being a good contributor? being a good animator? knowing the boss? We explore this question looking at the process of election for administrator in the English Wikipedia community. We modeled the candidates according to their revisions and/or social attributes. These attributes are used to construct a predictive model of promotion success, based on the candidates's past behavior, computed thanks to a random forest algorithm. Our model combining knowledge contribution variables and social networking variables successfully explain 78% of the results which is better than the former models. It also helps to refine the criterion for election. If the number of knowledge contributions is the most important element, social interactions come close second to explain the election. But being connected with the future peers (the admins) can make the difference between success and failure, making this epistemic community a very social community too

Proton and Helium Spectra from the CREAM-III Flight

Primary cosmic-ray elemental spectra have been measured with the balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment since 2004. The third CREAM payload (CREAM-III) flew for 29 days during the 2007-2008 Antarctic season. Energies of incident particles above 1 TeV are measured with a calorimeter. Individual elements are clearly separated with a charge resolution of ~0.12 e (in charge units) and ~0.14 e for protons and helium nuclei, respectively, using two layers of silicon charge detectors. The measured proton and helium energy spectra at the top of the atmosphere are harder than other existing measurements at a few tens of GeV. The relative abundance of protons to helium nuclei is 9.53+-0.03 for the range of 1 TeV/n to 63 TeV/n. The ratio is considerably smaller than other measurements at a few tens of GeV/n. The spectra become softer above ~20 TeV. However, our statistical uncertainties are large at these energies and more data are needed

Bioaccesibilidad de minerales mayoritarios y oligoelementos en distintas variedades de arroz cocido en Argentina

The objective of this work was to evaluate the total and bioaccessible concentration of elemental nutrients in rice varieties, from the provinces of Corrientes and Entre Ríos. The samples of cooked white rice, fine long and fortuna or double carolina varieties, were processed by standardized methods, like moisture, total proteins by Kjeldhal, fiber by a gravimetric-enzymatic method. The macroelements calcium and magnesium were evaluated by complexometry, phosphorus by UV-visible spectrophotometry, and the microelements iron, copper and zinc were performed by atomic absorption spectrophotometry. The bioaccessible fraction was determined by an in vitro dialysis method, using an enzyme complex and successive incubations reproducing the digestion process under physiological conditions. The results of total calcium ranged between 50 mg/100g of the double carolina variety from Corrientes and 87 mg/100g of the fine long from the same province, the dialyzable calcium was between 15 and 16%, the total phosphorus ranged between 39.4 mg/100g in fine long and 56.2 mg/100g in double carolina, both from Entre Ríos, and the dialysable fraction varied between 15 and 20%, the total magnesium content fluctuated between 30.0 mg/100g and 51.0 mg/100g and the dialyzable between 22 and 31%. Regarding iron, it had total concentrations of 6 mg/kg in fine long rice, with 60% of dialyzable fraction and 12 mg/kg in double caroline, but with 35% of dialyzability. Total copper yielded values between 3.45 mg/kg and 5.70 mg/kg with 6 to 30% dialysed fraction. The total zinc content varied between 10.21 mg/kg and 11.48 mg/kg, with a low bioaccessible fraction of 3%. It is concluded that the total and bioaccessible contents of these nutrients is initial information to promove a fortification program in rice, which is the most important crop in the region.El trabajo se realizó con el objetivo de dilucidar la concentración total y bioaccesible de nutrientes elementales en variedades de arroz de las provincias de Corrientes y Entre Ríos. Las muestras de arroz blanco cocido, del tipo largo fino y fortuna o doble carolina, se procesaron por métodos estandarizados, determinándose humedad, proteínas totales por Kjeldhal y fibra por método gravimétrico-enzimático. Los macrominerales calcio y magnesio se evaluaron por complexometría, el fósforo por espectrofotometría UV-visible, y los microelementos hierro, cobre y cinc por espectrofotometría de absorción atómica. La fracción bioaccesible se determinó por el método de diálisis in vitro, utilizando un complejo enzimático y sucesivas incubaciones reproduciendo el proceso de digestión en condiciones fisiológicas. Los resultados de calcio total oscilaron entre 50 mg/100 g de la variedad doble carolina de Corrientes y 87 mg/100 g del largo fino de la misma provincia, el calcio dializable fue entre un 15 y 16%, el fósforo total osciló entre 39,4 mg/100 g en largo fino y 56,2 mg/100 g en doble carolina, ambos entrerrianos y la fracción dializable varió entre 15 y 20%, el contenido de magnesio total fluctuó entre 30,0 mg/100 g y 51,0 mg/100 g y el dializable entre 22 y 31 %. Con respecto al hierro, tuvo concentraciones totales de 6 mg/kg en largo fino con un 60% de dializable y 12 mg/kg en doble carolina, pero con 35% de dializabilidad. El cobre total arrojó valores entre 3,45 mg/kg y 5,70 mg/kg con un 6 al 30% de fracción dializada. El contenido de cinc total varió entre 10,21 mg/kg y 11,48 mg/kg, con una baja fracción bioaccesible, del 3%. Se concluye que los contenidos totales y bioaccesibles de estos nutrientes, asumen una información inicial útil para favorecer un programa de fortificación del arroz, que constituye el cultivo alimentario más importante de la región

Status and Recent Results of the Acoustic Neutrino Detection Test System AMADEUS

The AMADEUS system is an integral part of the ANTARES neutrino telescope in the Mediterranean Sea. The project aims at the investigation of techniques for acoustic neutrino detection in the deep sea. Installed at a depth of more than 2000m, the acoustic sensors of AMADEUS are based on piezo-ceramics elements for the broad-band recording of signals with frequencies ranging up to 125kHz. AMADEUS was completed in May 2008 and comprises six "acoustic clusters", each one holding six acoustic sensors that are arranged at distances of roughly 1m from each other. The clusters are installed with inter-spacings ranging from 15m to 340m. Acoustic data are continuously acquired and processed at a computer cluster where online filter algorithms are applied to select a high-purity sample of neutrino-like signals. 1.6 TB of data were recorded in 2008 and 3.2 TB in 2009. In order to assess the background of neutrino-like signals in the deep sea, the characteristics of ambient noise and transient signals have been investigated. In this article, the AMADEUS system will be described and recent results will be presented.Comment: 7 pages, 8 figures. Proceedings of ARENA 2010, the 4th International Workshop on Acoustic and Radio EeV Neutrino Detection Activitie

Providing Personalized Guidance in Arithmetic Problem Solving

Supervising a student's resolution of an arithmetic word problem is a cumbersome task. Di erent students may use di erent lines of reasoning to reach the nal solution, and the assistance provided should be consistent with the resolution path that the student has in mind. In addition, further learning gains can be achieved if the previous student's background is also considered in the process. In this paper, we outline a relatively simple method to adapt the hints given by an Intelligent Tutoring System to the line of reasoning that the student is currently following. We also outline possible extensions to build a model of the student's most relevant skills, by tracking user's actions