6,109 research outputs found
THE FIRST GRADE PRIVATE SCHOOL SECTOR: TAXONOMY, CHOICE, AND ACHIEVEMENT
Studies focusing on Catholic schools as a proxy for all private education or all private religious education miss important variances within the private school sector, especially at the first grade level. The implication of this is that the vast majority of secondary school choice studies are incomplete; the elementary schooling decision of the parents should be included for all secondary school choice analyses. I augment the scope of a households first grade schooling choice by offering a rich model that includes the public schooling option and the most detailed typology of private schools to date: Catholic, Evangelical or Fundamental Protestant, Mainline Protestant or Other Faith, and Secular. Upon selecting a school type, I evaluate a students performance within this selected sector. While critics argue that selection and omitted variable biases generate test score gains for students rather than private school superiority, I include a childs fall kindergarten reading, math, and general knowledge test scores to control for a students knowledge acquired prior to kindergarten enrollment. I examine whether higher first grade test scores are the result of selection into the private sector or preeminence of the private sector. I find kindergarten test performance, household income, and parental education are significant and positive factors in selecting a school. Additionally, household religiosity and the denominational composition in the households home county are also significant determinants of schooling choice. Results from voucher simulations indicate that an increase in private school attendance does not translate to uniform enrollment increases at all types of private schools. White and Hispanic girls display similar patterns for Catholic and Protestant schools while African-American and white girls select Evangelical schools in analogous trends. Findings suggest that, while a students ability is the driving force behind first grade achievement, the type of school attended in first grade does affect a childs test score for all three tests. First grade private school enrollment makes below average achievers in kindergarten into better students in the first grade. Private schools offer no significant benefit for first grade enrollment to high achieving kindergarten students
Quantised orbital angular momentum transfer and magnetic dichroism in the interaction of electron vortices with matter
Following the very recent experimental realisation of electron vortices, we
consider their interaction with matter, in particular the transfer of orbital
angular momentum in the context of electron energy loss spectroscopy, and the
recently observed dichroism in thin film magnetised iron samples. We show here
that orbital angular momentum exchange does indeed occur between electron
vortices and the internal electronic-type motion, as well as center of mass
motion of atoms in the electric dipole approximation. This contrasts with the
case of optical vortices where such transfer only occurs in transitions
involving multipoles higher than the dipole. The physical basis of the observed
dichroism is explained
Experimental Implementation of the Quantum Baker's Map
This paper reports on the experimental implementation of the quantum baker's
map via a three bit nuclear magnetic resonance (NMR) quantum information
processor. The experiments tested the sensitivity of the quantum chaotic map to
perturbations. In the first experiment, the map was iterated forward and then
backwards to provide benchmarks for intrinsic errors and decoherence. In the
second set of experiments, the least significant qubit was perturbed in between
the iterations to test the sensitivity of the quantum chaotic map to applied
perturbations. These experiments are used to investigate previous predicted
properties of quantum chaotic dynamics.Comment: submitted to PR
Fidelity Decay as an Efficient Indicator of Quantum Chaos
Recent work has connected the type of fidelity decay in perturbed quantum
models to the presence of chaos in the associated classical models. We
demonstrate that a system's rate of fidelity decay under repeated perturbations
may be measured efficiently on a quantum information processor, and analyze the
conditions under which this indicator is a reliable probe of quantum chaos and
related statistical properties of the unperturbed system. The type and rate of
the decay are not dependent on the eigenvalue statistics of the unperturbed
system, but depend on the system's eigenvector statistics in the eigenbasis of
the perturbation operator. For random eigenvector statistics the decay is
exponential with a rate fixed precisely by the variance of the perturbation's
energy spectrum. Hence, even classically regular models can exhibit an
exponential fidelity decay under generic quantum perturbations. These results
clarify which perturbations can distinguish classically regular and chaotic
quantum systems.Comment: 4 pages, 3 figures, LaTeX; published version (revised introduction
and discussion
Quantization of Hyperbolic N-Sphere Scattering Systems in Three Dimensions
Most discussions of chaotic scattering systems are devoted to two-dimensional
systems. It is of considerable interest to extend these studies to the, in
general, more realistic case of three dimensions. In this context, it is
conceptually important to investigate the quality of semiclassical methods as a
function of the dimensionality. As a model system, we choose various three
dimensional generalizations of the famous three disk problem which played a
central role in the study of chaotic scattering in two dimensions. We present a
quantum-mechanical treatment of the hyperbolic scattering of a point particle
off a finite number of non-overlapping and non-touching hard spheres in three
dimensions. We derive expressions for the scattering matrix S and its
determinant. The determinant of S decomposes into two parts, the first one
contains the product of the determinants of the individual one-sphere
S-matrices and the second one is given by a ratio involving the determinants of
a characteristic KKR-type matrix and its conjugate. We justify our approach by
showing that all formal manipulations in these derivations are correct and that
all the determinants involved which are of infinite dimension exist. Moreover,
for all complex wave numbers, we conjecture a direct link between the
quantum-mechanical and semiclassical descriptions: The semiclassical limit of
the cumulant expansion of the KKR-type matrix is given by the Gutzwiller-Voros
zeta function plus diffractional corrections in the curvature expansion. This
connection is direct since it is not based on any kind of subtraction scheme
involving bounded reference systems. We present numerically computed resonances
and compare them with the corresponding data for the similar two-dimensional
N-disk systems and with semiclassical calculations.Comment: 35 pages, LaTeX plus 8 Postscript figures, uses epsf.sty, epsfig.sty
and epsf.te
NMR C-NOT gate through Aharanov-Anandan's phase shift
Recently, it is proposed to do quantum computation through the Berry's
phase(adiabatic cyclic geometric phase) shift with NMR (Jones et al, Nature,
403, 869(2000)). This geometric quantum gate is hopefully to be fault tolerant
to certain types of errors because of the geometric property of the Berry
phase. Here we give a scheme to realize the NMR C-NOT gate through
Aharonov-Anandan's phase(non-adiabatic cyclic phase) shift on the dynamic phase
free evolution loop.
In our scheme, the gate is run non-adiabatically, thus it is less affected by
the decoherence. And, in the scheme we have chosen the the zero dynamic phase
time evolution loop in obtaining the gepmetric phase shift, we need not take
any extra operation to cancel the dynamic phase.Comment: 5 pages, 1 figur
What makes good feedback good?
HE institutions persistently seek to increase student engagement and satisfaction with assessment feedback, but with limited success. This study identifies the attributes of good feedback from the perspective of recipients. In a distinctive participatory research design, student participants were invited to bring along actual examples of feedback that they perceived as either ‘good’ or ‘bad’ to 32 interviews with student researchers. Findings highlight the complex interdependency and contextual nature of key influences on students’ perspectives. The feedback artefact itself, its place in assessment and feedback design, relationships of the learner with peers and tutors, and students’ assessment literacy all affect students’ perspectives. We conclude that standardising the technical aspects of feedback, such as the feedback artefact or the timing or medium of its delivery is insufficient: a broader consideration of all key domains of influence is needed to genuinely increase student engagement and satisfaction with feedback
Efficient Algorithms for Universal Quantum Simulation
A universal quantum simulator would enable efficient simulation of quantum
dynamics by implementing quantum-simulation algorithms on a quantum computer.
Specifically the quantum simulator would efficiently generate qubit-string
states that closely approximate physical states obtained from a broad class of
dynamical evolutions. I provide an overview of theoretical research into
universal quantum simulators and the strategies for minimizing computational
space and time costs. Applications to simulating many-body quantum simulation
and solving linear equations are discussed
On the Interpretation of Energy as the Rate of Quantum Computation
Over the last few decades, developments in the physical limits of computing
and quantum computing have increasingly taught us that it can be helpful to
think about physics itself in computational terms. For example, work over the
last decade has shown that the energy of a quantum system limits the rate at
which it can perform significant computational operations, and suggests that we
might validly interpret energy as in fact being the speed at which a physical
system is "computing," in some appropriate sense of the word. In this paper, we
explore the precise nature of this connection. Elementary results in quantum
theory show that the Hamiltonian energy of any quantum system corresponds
exactly to the angular velocity of state-vector rotation (defined in a certain
natural way) in Hilbert space, and also to the rate at which the state-vector's
components (in any basis) sweep out area in the complex plane. The total angle
traversed (or area swept out) corresponds to the action of the Hamiltonian
operator along the trajectory, and we can also consider it to be a measure of
the "amount of computational effort exerted" by the system, or effort for
short. For any specific quantum or classical computational operation, we can
(at least in principle) calculate its difficulty, defined as the minimum effort
required to perform that operation on a worst-case input state, and this in
turn determines the minimum time required for quantum systems to carry out that
operation on worst-case input states of a given energy. As examples, we
calculate the difficulty of some basic 1-bit and n-bit quantum and classical
operations in an simple unconstrained scenario.Comment: Revised to address reviewer comments. Corrects an error relating to
time-ordering, adds some additional references and discussion, shortened in a
few places. Figures now incorporated into tex
The Edge of Quantum Chaos
We identify a border between regular and chaotic quantum dynamics. The border
is characterized by a power law decrease in the overlap between a state evolved
under chaotic dynamics and the same state evolved under a slightly perturbed
dynamics. For example, the overlap decay for the quantum kicked top is well
fitted with (with the nonextensive entropic
index and depending on perturbation strength) in the region
preceding the emergence of quantum interference effects. This region
corresponds to the edge of chaos for the classical map from which the quantum
chaotic dynamics is derived.Comment: 4 pages, 4 figures, revised version in press PR
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