1,633 research outputs found
Universal quantum computing with correlated spin-charge states
We propose a universal quantum computing scheme in which the orthogonal qubit
states and are identical in their single-particle spin and charge
properties. Each qubit is contained in a single quantum dot and gate operations
are induced all-electrically by changes in the confinement potential. Within
the computational space, these qubits are robust against environmental
influences that couple to the system through single-particle channels. Due to
the identical spin and charge properties of the , states, the
lowest-order relaxation and decoherence rates and , within the
Born-Markov approximation, both vanish for a large class of environmental
couplings. We give explicit pulse sequences for a universal set of gates
(phase, , Hadamard, \textsc{cnot}) and discuss state preparation,
manipulation, and detection.Comment: 6 pages, 3 eps figures, revtex
Nonlinear sigma Model Treatment of Quantum Antiferromagnets in a Magnetic Field
We present a theoretical analysis of the properties of low-dimensional
quantum antiferromagnets in applied magnetic fields. In a nonlinear sigma model
description, we use a spin stiffness analysis, a 1/N expansion, and a
renormalization group approach to describe the broken-symmetry regimes of
finite magnetization, and, in cases of most interest, a low-field regime where
symmetry is restored by quantum fluctuations. We compute the magnetization,
critical fields, spin correlation functions, and decay exponents accessible by
nuclear magnetic resonance experiments. The model is relevant to many systems
exhibiting Haldane physics, and provides good agreement with data for the
two-chain spin ladder compound CuHpCl.Comment: 14 pages, 6 figures, full paper to accompany cond-mat/980415
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 -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 ,
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
Decomposition and Gluing for Adiabatic Quantum Optimization
Farhi and others have introduced the notion of solving NP problems using
adiabatic quantum com- puters. We discuss an application of this idea to the
problem of integer factorization, together with a technique we call gluing
which can be used to build adiabatic models of interesting problems. Although
adiabatic quantum computers already exist, they are likely to be too small to
directly tackle problems of interesting practical sizes for the foreseeable
future. Therefore, we discuss techniques for decomposition of large problems,
which permits us to fully exploit such hardware as may be available. Numerical
re- sults suggest that even simple decomposition techniques may yield
acceptable results with subexponential overhead, independent of the performance
of the underlying device.Comment: 15 pages, many figure
Equity Valuation : United States Steel Corporation
This dissertation aims to determine the price target of United States Steel Corporation, a steel
manufacturing company of historical significance which has recently experienced profitability
issues. Despite previous issues the company finds itself in a transitionary environment towards
sustainability, presenting a unique opportunity for the company to rebound from several years of
financial mediocracy compared to its peers.
In pursue of the fair value of U.S. Steel two model will be utilized, for the fundamental analysis a
DCF model will be performed and for the relative valuation a Comparable Company Analysis
(CCA) also known as a multiple’s valuation. Within the DCF three scenarios will be computed to
depict the different economic environments that the company may undergo, with those being an
optimistic, a recession and a base scenario. For each respective scenario, assumptions have been
made which conform with the company strategy and macro-economic landscape.
Following the research and assumptions considered the price target for U.S. Steel comes to 21.36 per share.Esta dissertação tem por objetivo determinar o preço-alvo da United States Steel Corporation, uma
empresa siderúrgica de importância histórica que recentemente tem tido problemas de
rentabilidade. Apesar destes problemas, a empresa encontra-se num ambiente de transição para a
sustentabilidade, apresentando uma oportunidade única para recuperar de vários anos de
mediocracia financeira em comparação com os seus concorrentes.
Para determinar o valor justo da U.S. Steel, serão utilizados dois modelos: para a análise
fundamental, será utilizado um modelo de Discounted Cash Flow e, para a avaliação relativa, uma
análise de empresas comparáveis (CCA), também conhecida como avaliação por múltiplos. No
âmbito do DCF, serão calculados três cenários para representar os diferentes ambientes
económicos que a empresa pode atravessar, sendo estes um cenário optimista, um de recessão e
um cenário base. Para cada um dos respetivos cenários, foram feitas suposições que estão em
conformidade com a estratégia da empresa e o panorama macroeconómico.
Após a pesquisa e os pressupostos considerados, o preço-alvo para a U.S. Steel é de 21,36 por acção
Why was it important for the Byzantines to read Latin? The views of Demetrios Kydones (1324-1398)
Abstract: Fourteenth-century Byzantium witnessed civil wars between cliques of the ruling elite, constant financial crisis and dramatic territorial reduction. As a result of two catastrophic civil wars that were fought in 1321-1328 and 1341-1347, the Byzantine empire evolved into a small state which was struggling to survive and defend itself against large numbers of hostile neighbours, some of whom had or gradually acquired the resources to develop military forces far superior to those of Byzantium. In the 1350s and1360s the Ottoman Turks began the conquest of European territories that belonged to the Byzantine empire and threatened the very existence of the Byzantine state. Seeing that it was impossible to face the Ottomans militarily many Byzantines began to support the idea of a Crusade against the Ottomans and the reconciliation between the Orthodox and the Catholic Churches. One of the most staunchest supporters of this policy was the prolific author and politician Demetrios Kydones. This article will discuss how Kydones promoted the policy of reconciliation and alliance with Western European powers against the Ottomans
- …