1,390 research outputs found
Measuring the quantum state of a single system with minimum state disturbance
Conventionally, unknown quantum states are characterized using quantum-state
tomography based on strong or weak measurements carried out on an ensemble of
identically prepared systems. By contrast, the use of protective measurements
offers the possibility of determining quantum states from a series of weak,
long measurements performed on a single system. Because the fidelity of a
protectively measured quantum state is determined by the amount of state
disturbance incurred during each protective measurement, it is crucial that the
initial quantum state of the system is disturbed as little as possible. Here we
show how to systematically minimize the state disturbance in the course of a
protective measurement, thus enabling the maximization of the fidelity of the
quantum-state measurement. Our approach is based on a careful tuning of the
time dependence of the measurement interaction and is shown to be dramatically
more effective in reducing the state disturbance than the previously considered
strategy of weakening the measurement strength and increasing the measurement
time. We describe a method for designing the measurement interaction such that
the state disturbance exhibits polynomial decay to arbitrary order in the
inverse measurement time . We also show how one can achieve even faster,
subexponential decay, and we find that it represents the smallest possible
state disturbance in a protective measurement. In this way, our results show
how to optimally measure the state of a single quantum system using protective
measurements.Comment: 7 pages, 4 figures, identical to published versio
Breakdown of the perturbative renormalization group for S >= 1 random antiferromagnetic spin chains
We investigate the application of a perturbative renormalization group (RG)
method to random antiferromagnetic Heisenberg chains with arbitrary spin size.
At zero temperature we observe that initial arbitrary probability distributions
develop a singularity at J=0, for all values of spin S. When the RG method is
extended to finite temperatures, without any additional assumptions, we find
anomalous results for S >= 1. These results lead us to conclude that the
perturbative scheme is not adequate to study random chains with S >= 1.
Therefore a random singlet phase in its more restrictive definition is only
assured for spin-1/2 chains.Comment: 5 pages, 3 figures. To appear in Physical Review
Delayed-choice quantum eraser for the undergraduate laboratory
In a delayed-choice quantum eraser, interference fringes are obtained by
erasing which-way information after the interfering particle has already been
irreversibly detected. Following an introductory review of delayed-choice
experiments and quantum erasure, we describe the experimental realization of an
optical delayed-choice quantum eraser, suitable for advanced undergraduates,
based on polarization-entangled pairs of single photons. In our experiment, the
delay of the erasure is implemented using two different setups. The first setup
employs an arrangement of mirrors to increase the optical path length of the
photons carrying which-way information. In the second setup, we use fiber-optic
cables to elongate the path of these photons after their passage through the
polarization analyzer but prior to their arrival at the detector. We compare
our results to data obtained in the absence of a delay and find excellent
agreement. This shows that the timing of the erasure is irrelevant, as also
predicted by quantum mechanics. The experiment can serve as a valuable
pedagogical tool for conveying the fundamentals of quantum mechanics.Comment: 13 pages, 5 figures, identical to published versio
Leveraging University-School District Research Partnerships: Exploring the Longitudinal Effects of an Early Kindergarten Transition Program
With increasingly tight budgets, many public school districts lack research personnel to evaluate program efficacy or investigate best practices that raise student achievement. We highlight an example of a successful university-district partnership that offers district-driven research support while providing opportunities for practitioner-scholars to learn first-hand how to perform rigorous evaluation work. This article details the Early Kindergarten Transition program evaluation study conducted by a university-district partnership as well as testimony from district leadership on the utility of the research deliverables and long-term benefits of the research collaboration
No-go theorem for the composition of quantum systems
Building on the Pusey-Barrett-Rudolph theorem, we derive a no-go theorem for
a vast class of deterministic hidden-variables theories, including those
consistent on their targeted domain. The strength of this result throws doubt
on seemingly natural assumptions (like the "preparation independence" of the
Pusey-Barrett-Rudolph theorem) about how "real states" of subsystems compose
for joint systems in nonentangled states. This points to constraints in
modeling tensor-product states, similar to constraints demonstrated for more
complex states by the Bell and Bell-Kochen-Specker theorems.Comment: 4 pages. v2: new title, significant revisions. v3: condensed, matches
final published versio
Religion in Schools? The Importance of Recognizing the Impact of Religious Experiences
The school environment is a place of forced contact between diverse peoples. It is the perfect environment to nurture the diverse identities present. The influences on identity (i.e., language, ethnicity, religion, etc.) shape how students perceive information and learn. Some educators use these influences to help them instruct students. However, often overlooked is the influence of religious practices on language use and behavior in classrooms. This paper argues that the significance of understanding the religious practices of students is equally as important for planning instruction as knowing any other aspect of their culture, (i.e., the students’ native language(s)). Framed by principles of interfaith dialogue, the paper highlights a few examples of language use and behavior at the intersection of religion and education. The author argues that using the religious beliefs of students as strengths of their identity might eliminate some of the misunderstandings in the classroom and help establish an environment of mutual acceptance which might lead to deeper learning. Additionally, dialogue that includes aspects of religious practices might help students makes sense of the world and foster collaboration in the larger society
Quantum fidelity approach to the ground state properties of the 1D ANNNI model in a transverse field
In this work we analyze the ground-state properties of the
one-dimensional ANNNI model in a transverse field using the quantum fidelity
approach. We numerically determined the fidelity susceptibility as a function
of the transverse field and the strength of the next-nearest-neighbor
interaction , for systems of up to 24 spins. We also examine the
ground-state vector with respect to the spatial ordering of the spins. The
ground-state phase diagram shows ferromagnetic, paramagnetic, floating,
phases, and we predict an infinite number of modulated phases in
the thermodynamic limit (). The transition lines
separating the modulated phases seem to be of second-order, whereas the line
between the floating and the phases is possibly of first-order.Comment: 10 pages, 20 figure
Student Nurse Perceptions of Effective Medication Administration Education
Nursing faculty strive to educate students in a manner that prevents errors, promoting quality, patient-centered care. This endeavor is dependent upon meaningful and effective education that incorporates educational experiences reflective of the service sector. Anecdotal reports from clinical faculty and student nurses suggest that academic medication administration education may not optimally prepare students for safe entry into clinical practice. The aim of this phenomenologic qualitative research is to understand student nurse perceptions regarding teaching strategies and learning activities that prepared them for safe medication administration in acute care clinical settings. Focus group interviews resulted in two broad themes that are identified as Effective Education and Gaps in Education. Within these broad themes, findings revealed that students value faculty demonstrations, peer-learning opportunities, and repetitive practice with timely feedback. Study findings also pointed to educational gaps. Students reported needing to learn communication and conflict resolution strategies that would help them manage real-world interruptions, distractions, and computer generated alerts. Study findings recommend implementing relevant decision-support technology within academic lab learning activities
Self-induced decoherence approach: Strong limitations on its validity in a simple spin bath model and on its general physical relevance
The "self-induced decoherence" (SID) approach suggests that (1) the
expectation value of any observable becomes diagonal in the eigenstates of the
total Hamiltonian for systems endowed with a continuous energy spectrum, and
(2), that this process can be interpreted as decoherence. We evaluate the first
claim in the context of a simple spin bath model. We find that even for large
environments, corresponding to an approximately continuous energy spectrum,
diagonalization of the expectation value of random observables does in general
not occur. We explain this result and conjecture that SID is likely to fail
also in other systems composed of discrete subsystems. Regarding the second
claim, we emphasize that SID does not describe a physically meaningful
decoherence process for individual measurements, but only involves destructive
interference that occurs collectively within an ensemble of presupposed
"values" of measurements. This leads us to question the relevance of SID for
treating observed decoherence effects.Comment: 11 pages, 4 figures. Final published versio
Ecology and the Common Good: Sustainability and Catholic Social Teaching
In recent years official Roman Catholic documents have addressed the ecological
crisis from the perspective of Catholic social teaching. This expansion of Catholic social
thought addresses the social and ecological question. This paper links environmental and human ecology with the concept of sustainability and proposes an interpretation of the common good and a definition of sustainability within Catholic social teaching. Our treatment of sustainability and Catholic social teaching includes: an analysis of the
ecological processes that sustain nature; insights from human ecology, and an
examination of models of sustainability as a foundation for re-structuring society to
promote the common good. The paper provides a summary of the historical expansion of the common good within modern Catholic social thought, and concludes with an
ecological interpretation of the common good and a definition of sustainability within the Catholic understanding of justice
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