From Classical State-Swapping to Quantum Teleportation

The quantum teleportation protocol is extracted directly out of a standard classical circuit that exchanges the states of two qubits using only controlled-NOT gates. This construction of teleportation from a classically transparent circuit generalizes straightforwardly to d-state systems.Comment: Missing daggers added to Figures 13, 14, and 15. Otherwise this is the version that appeared in Physical Revie

Bayes and Blickets: Effects of Knowledge on Causal Induction in Children and Adults

People are adept at inferring novel causal relations, even from only a few observations. Prior knowledge about the probability of encountering causal relations of various types and the nature of the mechanisms relating causes and effects plays a crucial role in these inferences. We test a formal account of how this knowledge can be used and acquired, based on analyzing causal induction as Bayesian inference. Five studies explored the predictions of this account with adults and 4-year-olds, using tasks in which participants learned about the causal properties of a set of objects. The studies varied the two factors that our Bayesian approach predicted should be relevant to causal induction: the prior probability with which causal relations exist, and the assumption of a deterministic or a probabilistic relation between cause and effect. Adults’ judgments (Experiments 1, 2, and 4) were in close correspondence with the quantitative predictions of the model, and children’s judgments (Experiments 3 and 5) agreed qualitatively with this account.Mitsubishi Electronic Research LaboratoriesUnited States. Air Force Office of Sponsored ResearchMassachusetts Institute of Technology. Paul E. Newton ChairJames S. McDonnell Foundatio

Classicality of quantum information processing

The ultimate goal of the classicality programme is to quantify the amount of quantumness of certain processes. Here, classicality is studied for a restricted type of process: quantum information processing (QIP). Under special conditions, one can force some qubits of a quantum computer into a classical state without affecting the outcome of the computation. The minimal set of conditions is described and its structure is studied. Some implications of this formalism are the increase of noise robustness, a proof of the quantumness of mixed state quantum computing and a step forward in understanding the very foundation of QIP.Comment: Minor changes, published in Phys. Rev. A 65, 42319 (2002

Struggles, strengths, and strategies: an ethnographic study exploring the experiences of adolescents living with an ostomy

<p>Abstract</p> <p>Background</p> <p>Adolescents with IBD requiring ostomy surgery experience perioperative needs that may exceed those of patients experiencing other major abdominal surgery <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>. This procedure requires ongoing and vigilant daily care and management. Gastrointestinal symptoms and complications impose psychological and social stresses on young patients <abbrgrp><abbr bid="B2">2</abbr></abbrgrp>, and the procedure results in body image changes and daily regimens of self-care. This study aimed to explore adolescents' experiences and quality of life following ostomy surgery.</p> <p>Methods</p> <p>Ethnographic interviews and a subsequent focus group were conducted with 20 adolescents with an ostomy or j-pouch being treated at the Hospital for Sick Children in Toronto, Canada. Interviews were transcribed verbatim and subjected to theme generation.</p> <p>Results</p> <p>Findings suggest that adolescents are profoundly affected by their ostomy. Adolescents convey strength as well as adjustment struggles. Identified impacts include body intrusion and body image changes, decreased independence, secrecy about the ostomy, adjustment over time, challenges for the family, and strategies for constructively moving forward.</p> <p>Conclusion</p> <p>Implications address the importance of ensuring meaningful opportunities to understand and reframe the stresses of illness. An ongoing clinical challenge involves the promotion of a healthy self-esteem and psychosocial adjustment for these adolescents and their families. Finding effective ways to minimize stress and embarrassment and reframe personal shame, constitute important clinical priorities. Opportunities for peer support and family dialogue may assist in clarifying worries and easing the burden carried by these young persons. Flexible and adequately funded resources are advocated in fostering quality of life.</p

The Sheffield Caseload Classification Tool: testing its inter-rater reliability.

Community nursing caseloads are vast, with differing complexities. The Sheffield Caseload Classification Tool (SCCT) was co-produced with community nurses and nurse managers to help assign patients on a community caseload according to nursing need and complexity of care. The tool comprises 12 packages of care and three complexities. The present study aimed to test the inter-rater reliability of the tool. This was a table top validation exercise conducted in one city in South Yorkshire. A purposive sample of six community nurses assessed 69 case studies using the tool and assigned a package of care and complexity of need to each. These were compared with pre-determined answers. Cronbach's alpha for the care package was 0.979, indicating very good reliability, with individual nurse reliability values also being high. Fleiss's kappa coefficient for the care packages was 0.771, indicating substantial agreement among nurses; it was 0.423 for complexity ratings, indicating moderate agreement. The SCCT can reliably assign patients to the appropriate skilled nurse and care package. It helps prioritise and plan a community nursing caseload, ensuring efficient use of staff time to deliver appropriate care to patients with differing needs

Expanding perfect fluid generalizations of the C-metric

We reexamine Petrov type D gravitational fields generated by a perfect fluid with spatially homogeneous energy density and in which the flow lines form a timelike non-shearing and non-rotating congruence. It is shown that the anisotropic such spacetimes, which comprise the vacuum C-metric as a limit case, can have \emph{non-zero} expansion, contrary to the conclusion in the original investigation by Barnes (Gen. Rel. Grav. 4, 105 (1973)). This class consists of cosmological models with generically one and at most two Killing vectors. We construct their line element and discuss some important properties. The methods used in this investigation incite to deduce testable criteria regarding shearfree normality and staticity op Petrov type $D$ spacetimes in general, which we add in an appendix.Comment: 16 pages, extended and amended versio

Consistent Histories in Quantum Cosmology

We illustrate the crucial role played by decoherence (consistency of quantum histories) in extracting consistent quantum probabilities for alternative histories in quantum cosmology. Specifically, within a Wheeler-DeWitt quantization of a flat Friedmann-Robertson-Walker cosmological model sourced with a free massless scalar field, we calculate the probability that the univese is singular in the sense that it assumes zero volume. Classical solutions of this model are a disjoint set of expanding and contracting singular branches. A naive assessment of the behavior of quantum states which are superpositions of expanding and contracting universes may suggest that a "quantum bounce" is possible i.e. that the wave function of the universe may remain peaked on a non-singular classical solution throughout its history. However, a more careful consistent histories analysis shows that for arbitrary states in the physical Hilbert space the probability of this Wheeler-DeWitt quantum universe encountering the big bang/crunch singularity is equal to unity. A quantum Wheeler-DeWitt universe is inevitably singular, and a "quantum bounce" is thus not possible in these models.Comment: To appear in Foundations of Physics special issue on quantum foundation

Implications of adopting the WHO 2006 Child Growth Standards: case study from urban South Africa, the Birth to Twenty cohort

Background: The World Health Organization (WHO) recently developed growth standards to overcome the limitations of previous references. Aim: The aim of this study was to compare the growth patterns of a cohort of children using the National Centre for Health Statistics (NCHS), the Centre for Disease Control (CDC), and WHO 2006 references/standards, and to evaluate the implications of adopting WHO standards. Subjects and methods: Using growth data (0 5 years) from the 1990 South African Birth to Twenty cohort in Johannesburg-Soweto, Z-scores were derived for weight-for-age, length/height-for age, and weight-for-length/height from the NCHS and CDC references, and WHO 2006 standards. Results: The pattern of mean Z-score change observed when applying the NCHS and CDC references was similar to one another, but different to that obtained when using the WHO 2006 standard. WHO 2006 identified children as being generally more stunted and more overweight. Conclusion: Discourse on the implementation of WHO 2006 and the impact on the primary health care system and public health monitoring in South Africa is needed, and sufficient planning is critical around not only the implementation of WHO 2006 but also maintaining comparability with historical malnutrition data