On-chip cavity quantum phonodynamics with an acceptor qubit in silicon

We describe a chip-based, solid-state analogue of cavity-QED utilizing acoustic phonons instead of photons. We show how long-lived and tunable acceptor impurity states in silicon nanomechanical cavities can play the role of a matter non-linearity for coherent phonons just as, e.g., the Josephson qubit plays in circuit-QED. Both strong coupling (number of Rabi oscillations ~ 100) and strong dispersive coupling (0.1-2 MHz) regimes can be reached in cavities in the 1-20 GHz range, enabling the control of single phonons, phonon-phonon interactions, dispersive phonon readout of the acceptor qubit, and compatibility with other optomechanical components such as phonon-photon translators. We predict explicit experimental signatures of the acceptor-cavity system.Comment: 6 pages, 2 figures, PDFLaTeX. New version improves clarit

Some factors affecting agricultural production .and productivity in Iraq including selected climate variables and crops

In this study of factors affecting Iraqi agricultural production and productivity, it has been found essential to deal both with socioeconomic and technical factors on the one hand and environmental conditons on the other. The ultimate objective of this study is to assess the impact of selected climatic factors on the production and productivity of some principal crops. Such assessment, however, cannot be achieved in isolation from the influence of the socio-economic and technical factors. Considerable variability over time of the latter factors, caused by specific institutional changes such as the land reform of 1958, resulted in changes in agricultural conditions as a whole. Therefore, in Chapters Two to Nine are examined the national and regional conditions of Iraqi agriculture during the 1950-1975 period, i.e. planning and investment, land utilization, land tenure system and land reform, agricultural cooperatives and other organizations, new input factors including farm machinery and, finally, water resources and irrigation methods. The inescapable conclusion of this section of the study is that there were no significant medium or long-term improvement trends in the yields of principal crops despite varying but considerable additional inputs and planning attention. Moreover, the controls exerted by climate and weather appear crucial factors in both the irrigated and rainfed area. In Chapters Ten and Eleven we therefore turn to a direct examination of climatic and weather factors. In Chapters Twelve and Thirteen a study is made of the relationship between selected weather variables, i.e. rainfall, temperature and relative humidity, and wheat and barley yield. These two crops were chosen because of their importance to Iraqi agriculture as a whole, and in particular to the rainfed area of northern Iraq where environmental modifications by man are least strong. The first point appearing from this analysis shows that yields of these two crops are significantly affected by climatic and weather factors during specific periods within the growing season. The significance of statistical correlations between yields and certain critical climatic factors appear sufficiently valid for crop forecasting with a certain degree of accuracy. As a by-product of this analysis, it appears that there was a significant dislocation period following the implementation of land reform measures. In conclusion, it is clear that agricultural production and productivity must be dealt with in the context of a whole set of factors, socio-economic, technical and environmental, if significant developments in agriculture and rural welfare are to be achieved

Kinetic Monte Carlo Simulations of Crystal Growth in Ferroelectric Alloys

The growth rates and chemical ordering of ferroelectric alloys are studied with kinetic Monte Carlo (KMC) simulations using an electrostatic model with long-range Coulomb interactions, as a function of temperature, chemical composition, and substrate orientation. Crystal growth is characterized by thermodynamic processes involving adsorption and evaporation, with solid-on-solid restrictions and excluding diffusion. A KMC algorithm is formulated to simulate this model efficiently in the presence of long-range interactions. Simulations were carried out on Ba(Mg_{1/3}Nb_{2/3})O_3 (BMN) type materials. Compared to the simple rocksalt ordered structures, ordered BMN grows only at very low temperatures and only under finely tuned conditions. For materials with tetravalent compositions, such as (1-x)Ba(Mg_{1/3}Nb_{2/3})O_3 + xBaZrO_3 (BMN-BZ), the model does not incorporate tetravalent ions at low-temperature, exhibiting a phase-separated ground state instead. At higher temperatures, tetravalent ions can be incorporated, but the resulting crystals show no chemical ordering in the absence of diffusive mechanisms.Comment: 13 pages, 16 postscript figures, submitted to Physics Review B Journa

Spin Readout and Initialization in a Semiconductor Quantum Dot

Electron spin qubits in semiconductors are attractive from the viewpoint of long coherence times. However, single spin measurement is challenging. Several promising schemes incorporate ancillary tunnel couplings that may provide unwanted channels for decoherence. Here, we propose a novel spin-charge transduction scheme, converting spin information to orbital information within a single quantum dot by microwave excitation. The same quantum dot can be used for rapid initialization, gating, and readout. We present detailed modeling of such a device in silicon to confirm its feasibility.Comment: Published versio

Partial discharges location in power transformers using piezoceramic sensors

The detection and the spatial localization of partial discharges in high-voltage electrical machines are considered as an effective method in predictive maintenance that can provide valuable information on the health of the insulation system and allow to determine accurately the location of the risky insulation elements, which in turn will avoid any premature equipment’s deterioration by scheduling preventive maintenance action. After confirming in a previous published paper the efficiency of a new generation of piezoceramics sensors (high temperature ultrasonic transducers) to detect and characterize partial discharges, we are going to investigate, in this work, a second potential of this technology to locate the partial discharge sources by relying on its ability to detect acoustic signals emitted by partial discharge sources. We will present experimental results, demonstrating the effectiveness of these sensors to locate partial discharges sources and, we will also present an algorithm for calculating the partial discharge foci, based on the acoustic wave flight time

Induced quantum dot probe for material characterization

We propose a non-destructive means of characterizing a semiconductor wafer via measuring parameters of an induced quantum dot on the material system of interest with a separate probe chip that can also house the measurement circuitry. We show that a single wire can create the dot, determine if an electron is present, and be used to measure critical device parameters. Adding more wires enables more complicated (potentially multi-dot) systems and measurements. As one application for this concept we consider silicon metal-oxide-semiconductor and silicon/silicon-germanium quantum dot qubits relevant to quantum computing and show how to measure low-lying excited states (so-called valley states). This approach provides an alternative method for characterization of parameters that are critical for various semiconductor-based quantum dot devices without fabricating such devices