Spin-orbit signatures in the dynamics of singlet-triplet qubits in double quantum dots

We characterize numerically and analytically the signatures of the spin-orbit interaction in a two-electron GaAs double quantum dot in the presence of an external magnetic field. In particular, we obtain the return probability of the singlet state by simulating Landau-Zener voltage detuning sweeps which traverse the singlet-triplet ($S-T_+$) resonance. Our results indicate that non-spin-conserving interdot tunneling processes arising from the spin-orbit interaction have well defined signatures. These allow direct access to the spin-orbit interaction scales and are characterized by a frequency shift and Fourier amplitude modulation of the Rabi flopping dynamics of the singlet-triplet qubits $S-T_0$ and $S-T_+$. By applying the Bloch-Feshbach projection formalism, we demonstrate analytically that the aforementioned effects originate from the interplay between spin-orbit interaction and processes driven by the hyperfine interaction between the electron spins and those of the GaAs nuclei

Linearized stability of charged thin-shell wormholes

The linearized stability of charged thin shell wormholes under spherically symmetric perturbations is analized. It is shown that the presence of a large value of charge provides stabilization to the system, in the sense that the constrains onto the equation of state are less severe than for non-charged wormholes.Comment: 8 pages, 2 figures; v2: minor changes. Accepted for publication in General Relativity and Gravitatio

Agent Based Test and Repair of Distributed Systems

This article demonstrates how to use intelligent agents for testing and repairing a distributed system, whose elements may or may not have embedded BIST (Built-In Self-Test) and BISR (Built-In Self-Repair) facilities. Agents are software modules that perform monitoring, diagnosis and repair of the faults. They form together a society whose members communicate, set goals and solve tasks. An experimental solution is presented, and future developments of the proposed approach are explore

Zero field spin splitting in AlSb/InAs/AlSb quantum wells induced by surface proximity effects

InAs quantum well heterostructures are of considerable interest for mesoscopic device applications such as scanning probe and magnetic recording sensors, which require the channel to be close to the surface. Here we report on magnetotransport measurements of AlSb/InAs/AlSb Hall bars at a shallow depth of 20 nm. Analysis of the observed Shubnikov-de Haas oscillations and modeling show that spin splitting energies in excess of 2.3 meV occur at zero magnetic field. We conclude that the spin-splitting results from the Rashba effect due to the band bending in the quantum well. This is caused by substantial electron transfer from the surface to the quantum well and becomes significant when the quantum well is located near the surface.Comment: 14 pages, 2 figures. (To be published in APL

The incidence of graft on developing-country firms

This paper measures the extent to which firms in developing countries are the target of bribes. Using new firm-level survey data from 33 African and Latin American countries, we first show that perceptions adjust slowly tofirms'experience with corrupt officials and hence are an imperfect proxy for the true incidence of graft. We then construct an experience-based index that reflects the probability that a firm will be asked for a bribe in order to complete a specified set of business transactions. On average, African firms are three times as likely to be asked for bribes as are firms in Latin America, although there is substantial variation within each region. Last, we show that graft appears to be more prevalent in countries with excessive regulation and where democracy is weak. In particular, our results suggest that the incidence of graft in Africa would fall by approximately 85 percent if countries in the region had levels of democracy and regulation similar to those that exist in Latin America.Public Sector Corruption&Anticorruption Measures,Corruption&Anitcorruption Law,Crime and Society,E-Business,Access to Finance

Agriculture Productivity Growth: Is the Current Trend on the Track to Poverty Reduction?

In this study we evaluate the effect of annual productivity growth in agriculture over the 1991-2001 period on poverty in eleven developing countries. We compare this with the optimal pattern of productivity growth of comparable cost with the sole goal of maximizing poverty reduction. This comparison reveals that regional agricultural development is a viable option in the fight for poverty reduction.Food Security and Poverty,