Coherent rotations of a single spin-based qubit in a single quantum dot at fixed Zeeman energy

Coherent rotations of single spin-based qubits may be accomplished electrically at fixed Zeeman energy with a qubit defined solely within a single electrostatically-defined quantum dot; the $g$-factor and the external magnetic field are kept constant. All that is required to be varied are the voltages on metallic gates which effectively change the shape of the elliptic quantum dot. The pseudospin-1/2 qubit is constructed from the two-dimensional $S=1/2$, $S_z=-1/2$ subspace of three interacting electrons in a two-dimensional potential well. Rotations are created by altering the direction of the pseudomagnetic field through changes in the shape of the confinement potential. By deriving an exact analytic solution to the long-range Coulomb interaction matrix elements, we calculate explicitly the range of magnitudes and directions the pseudomagnetic field can take. Numerical estimates are given for {GaAs}.Comment: Restructured manuscript, more details shown (results unchanged); Six pages, revtex4; More info at http://soliton.phys.dal.c

Money in the twenty-first century.

What implications do 21st century monetary innovations bring for holdings of central bank money and standards of value? Emerging technologies such as cybercash, e-cash, and smart cards can be expected to reduce demand for central bank money, but the theoretical framework for monetary policy has not changed. The authors stress three points in this paper: 1) money innovations tend to reduce the demand for central bank money, but it remains to be seen whether the predictability of that demand, and thus the reliability of monetary policy, will decline in the coming century; 2) in principle, monetary authorities can continue to determine the price level as long as final settlement of tax and other obligations takes place using central bank liabilities; and 3) the viability of competing currencies and standards of value is gaining steam as a lively field of research.Money ; Payment systems ; Smart cards

Constraining the Sub-AU-Scale Distribution of Hydrogen and Carbon Monoxide Gas around Young Stars with the Keck Interferometer

We present Keck Interferometer observations of T Tauri and Herbig Ae/Be stars with a spatial resolution of a few milliarcseconds and a spectral resolution of ~2000. Our observations span the K-band, and include the Br gamma transition of Hydrogen and the v=2-0 and v=3-1 transitions of carbon monoxide. For several targets we also present data from Keck/NIRSPEC that provide higher spectral resolution, but a seeing-limited spatial resolution, of the same spectral features. We analyze the Br gamma emission in the context of both disk and infall/outflow models, and conclude that the Br gamma emission traces gas at very small stellocentric radii, consistent with the magnetospheric scale. However some Br gamma-emitting gas also seems to be located at radii of >0.1 AU, perhaps tracing the inner regions of magnetically launched outflows. CO emission is detected from several objects, and we generate disk models that reproduce both the KI and NIRSPEC data well. We infer the CO spatial distribution to be coincident with the distribution of continuum emission in most cases. Furthermore the Br gamma emission in these objects is roughly coincident with both the CO and continuum emission. We present potential explanations for the spatial coincidence of continuum, Br gamma, and CO overtone emission, and explore the implications for the low occurrence rate of CO overtone emission in young stars. Finally, we provide additional discussion of V1685 Cyg, which is unusual among our sample in showing large differences in emitting region size and spatial position as a function of wavelength.Comment: Accepted for publication in MNRA

Two-point theory for the differential self-interrogation Feynman-alpha method

A Feynman-alpha formula has been derived in a two region domain pertaining the stochastic differential self-interrogation (DDSI) method and the differential die-away method (DDAA). Monte Carlo simulations have been used to assess the applicability of the variance to mean through determination of the physical reaction intensities of the physical processes in the two domains. More specifically, the branching processes of the neutrons in the two regions are described by the Chapman - Kolmogorov equation, including all reaction intensities for the various processes, that is used to derive a variance to mean relation for the process. The applicability of the Feynman-alpha or variance to mean formulae are assessed in DDSI and DDAA of spent fuel configurations.Comment: 15 pages, 5 figures. Submitted to EPJ Plu

Thrust-augmented vortex attenuation

An experimental investigation was conducted to determine the vortex attenuating effect of engine thrust. Tests were made using a 0.03-scale model of the Boeing 747 transport aircraft as a vortex generating model. A Learjet-class probe model was used to measure the vortex induced rolling moment at a scale separation distance of 1.63 km. These tests were conducted at a lift coefficient of 1.4 at a model velocity of 30.48 m/s. The data presented indicate that engine thrust is effective as a vortex attenuating device when the engines are operated at high thrust levels and are positioned to direct the high energy engine wake into the core of the vortex. The greatest thrust vortex attenuation was obtained by operating the inboard engine thrust reversers at one-quarter thrust and the outboard engines at maximum forward thrust

An investigation of the increase in vortex induced rolling moment associated with landing gear wake

Flight tests were conducted to verify the results found in ground base facilities of the effect of span lift load variation as well as the vortex attentuation of the high energy jet engine exhaust through proper thrust programming. During these flight tests a large increase in vortex strength was experienced as a result of extending the landing gear. Tests in the Langley Vortex Research Facility indicate that the wake produced by the landing gear may possibly form an aerodynamic endplate or reflection plane at the inboard edge of each inboard flap which increases the effective aspect ratio of the flap and thereby increases the strength of the flap outer edge vortex

INCOME REMINDER AND THE DIVERGENCE BETWEEN WILLINGNESS-TO-PAY ESTIMATES ASSOCIATED WITH DICHOTOMOUS CHOICE AND OPEN-ENDED ELICITATION FORMATS

This study investigates whether an income reminder can reduce the divergence between the willingness-to-pay (WTP) estimates associated with the open-ended (OE) and dichotomous choice (DC) elicitation formats. Results show that without an income reminder, WTP estimate associated with DC elicitation format is about 1.66 times as large as that associated with OE elicitation format. With an income reminder, the WTP estimate associated with DC format decreased while the WTP estimate associated with OE format increased, and the divergence between the WTP estimates was almost eliminated.dichotomous choice, open-ended, income reminder, water quality improvement, willingness-to-pay, Research Methods/ Statistical Methods,

Inhibition of type I interferon induction and signalling by mosquito-borne flaviviruses

The Flavivirus genus (Flaviviridae family) contains a number of important human pathogens, including dengue and Zika viruses, which have the potential to cause severe disease. In order to efficiently establish a productive infection in mammalian cells, flaviviruses have developed key strategies to counteract host immune defences, including the type I interferon response. They employ different mechanisms to control interferon signal transduction and effector pathways, and key research generated over the past couple of decades has uncovered new insights into their abilities to actively decrease interferon antiviral activity. Given the lack of antivirals or prophylactic treatments for many flaviviral infections, it is important to fully understand how these viruses affect cellular processes to influence pathogenesis and disease outcome. This review will discuss the strategies mosquito-borne flaviviruses have evolved to antagonise type I interferon mediated immune responses

A static air flow visualization method to obtain a time history of the lift-induced vortex and circulation

A recently proposed method of flow visualization was investigated at the National Aeronautics and Space Administration's Langley Research Center. This method of flow visualization is particularly applicable to the study of lift-induced wing tip vortices through which it is possible to record the entire life span of the vortex. To accomplish this, a vertical screen of smoke was produced perpendicular to the flight path and allowed to become stationary. A model was then driven through the screen of smoke producing the circular vortex motion made visible as the smoke was induced along the path taken by the flow and was recorded by highspeed motion pictures

Boundary and impurity effects on entanglement of Heisenberg chains

We study entanglement of a pair of qubits and the bipartite entanglement between the pair and the rest within open-ended Heisenberg $XXX$ and XY models. The open boundary condition leads to strong oscillations of entanglements with a two-site period, and the two kinds of entanglements are 180 degree out of phase with each other. The mean pairwise entanglement and ground-state energy per site in the $XXX$ model are found to be proportional to each other. We study the effects of a single bulk impurity on entanglement, and find that there exists threshold values of the relative coupling strength between the impurity and its nearest neighbours, after which the impurity becomes pairwise entangled with its nearest neighbours.Comment: 6 pages and 6 figure