Implementation of a Quantum Algorithm to Solve Deutsch's Problem on a Nuclear Magnetic Resonance Quantum Computer

We demonstrate the use of an NMR quantum computer based on the pyrimidine base cytosine, and the implementation of a quantum algorithm to solve Deutsch's problem.Comment: 16 pages including 6 figures. Minor clarifications as requested by the referee plus updated references. Journal of Chemical Physics, in press (expected publication date August 1st 1998

On Quantum Algorithms

Quantum computers use the quantum interference of different computational paths to enhance correct outcomes and suppress erroneous outcomes of computations. In effect, they follow the same logical paradigm as (multi-particle) interferometers. We show how most known quantum algorithms, including quantum algorithms for factorising and counting, may be cast in this manner. Quantum searching is described as inducing a desired relative phase between two eigenvectors to yield constructive interference on the sought elements and destructive interference on the remaining terms.Comment: 15 pages, 8 figure

Contaminated Communities: A video documentary of the Alberton, Montana mixed-chemical spill and an analysis of how its effects on toxics victims fits into a larger contamination framework from a political ecology perspective

The small rural mountain town of Alberton, MT located 32 miles west of Missoula, MT was the 1996 site of the largest contamination event in railroad history involving a mixture of chemicals. On April 11, 1996 a Montana Rail Link train derailed just west of the town of Alberton, leaking 130,000 pounds of chlorine gas, 17,000 of potassium cresylate (spent oil refinery waste), and 85 dry bulk pounds of sodium chlorate into the Alberton environment. Approximately 1000 people were evacuated from their homes, many for the seventeen day evacuation period that followed. The video documentary project that I embarked on in January 1997, the following year, attempts to chronicle the impact of this tragedy, on the lives of the evacuees from a political ecology perspective . It also documents the bureaucratic and medical responses to the changes in victims’ health and welfare over the course of the two and a half year period since the spill. The accompanying paper briefly describes the political ecology analysis of contamination events that guided my editing decisions for the documentary. The Appendix to this analysis contains a resource manual and action guide for preventing future Albertons, as well as an emergency response strategy for communities to follow, if such a tragedy does befall their community. The video documentary entitled A toxic train ran through it: a story of who benefits and who loses in toxic chemical catastrophes is included below as a mp4 video file. The video runs approximately 1 hour, 29 minutes, and 43 seconds

Single spin measurement using cellular automata techniques

We propose an approach for single spin measurement. Our method uses techniques from the theory of quantum cellular automata to correlate a large amount of ancillary spins to the one to be measured. It has the distinct advantage of being efficient, and to a certain extent fault-tolerant. Under ideal conditions, it requires the application of only order of cube root of N steps (each requiring a constant number of rf pulses) to create a system of N correlated spins. It is also fairly robust against pulse errors, imperfect initial polarization of the ancilla spin system, and does not rely on entanglement. We study the scalability of our scheme through numerical simulation.Comment: Submitted to Physical Review Letter

Resonant tunneling magnetoresistance in epitaxial metal-semiconductor heterostructures

We report on resonant tunneling magnetoresistance via localized states through a ZnSe semiconducting barrier which can reverse the sign of the effective spin polarization of tunneling electrons. Experiments performed on Fe/ZnSe/Fe planar junctions have shown that positive, negative or even its sign-reversible magnetoresistance can be obtained, depending on the bias voltage, the energy of localized states in the ZnSe barrier and spatial symmetry. The averaging of conduction over all localized states in a junction under resonant condition is strongly detrimental to the magnetoresistance

Bifidobacteria and lactobacilli in the gut microbiome of children with non-alcoholic fatty liver disease: which strains act as health players?

Introduction: Non-alcoholic fatty liver disease (NAFLD), considered the leading cause of chronic liver disease in children, can often progress from non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH). It is clear that obesity is one of the main risk factors involved in NAFLD pathogenesis, even if specific mechanisms have yet to be elucidated. We investigated the distribution of intestinal bifidobacteria and lactobacilli in the stools of four groups of children: obese, obese with NAFL, obese with NASH, and healthy, age-matched controls (CTRLs). Material and methods: Sixty-one obese, NAFL and NASH children and 54 CTRLs were enrolled in the study. Anthropometric and metabolic parameters were measured for all subjects. All children with suspected NASH underwent liver biopsy. Bifidobacteria and lactobacilli were analysed in children’s faecal samples, during a broader, 16S rRNA-based pyrosequencing analysis of the gut microbiome. Results: Three Bifidobacterium spp. (Bifidobacterium longum, Bifidobacterium bifidum, and Bifidobacterium adolescentis) and five Lactobacillus spp. (L. zeae, L. vaginalis, L. brevis, L. ruminis, and L. mucosae) frequently recurred in metagenomic analyses. Lactobacillus spp. increased in NAFL, NASH, or obese children compared to CTRLs. Particularly, L. mucosae was significantly higher in obese (p = 0.02426), NAFLD (p = 0.01313) and NASH (p = 0.01079) than in CTRLs. In contrast, Bifidobacterium spp. were more abundant in CTRLs, suggesting a protective and beneficial role of these microorganisms against the aforementioned diseases. Conclusions: Bifidobacteria seem to have a protective role against the development of NAFLD and obesity, highlighting their possible use in developing novel, targeted and effective probiotics

On the robustness of bucket brigade quantum RAM

We study the robustness of the bucket brigade quantum random access memory model introduced by Giovannetti, Lloyd, and Maccone [Phys. Rev. Lett. 100, 160501 (2008)]. Due to a result of Regev and Schiff [ICALP '08 pp. 773], we show that for a class of error models the error rate per gate in the bucket brigade quantum memory has to be of order $o(2^{-n/2})$ (where $N=2^n$ is the size of the memory) whenever the memory is used as an oracle for the quantum searching problem. We conjecture that this is the case for any realistic error model that will be encountered in practice, and that for algorithms with super-polynomially many oracle queries the error rate must be super-polynomially small, which further motivates the need for quantum error correction. By contrast, for algorithms such as matrix inversion [Phys. Rev. Lett. 103, 150502 (2009)] or quantum machine learning [Phys. Rev. Lett. 113, 130503 (2014)] that only require a polynomial number of queries, the error rate only needs to be polynomially small and quantum error correction may not be required. We introduce a circuit model for the quantum bucket brigade architecture and argue that quantum error correction for the circuit causes the quantum bucket brigade architecture to lose its primary advantage of a small number of "active" gates, since all components have to be actively error corrected.Comment: Replaced with the published version. 13 pages, 9 figure

Learning approaches used by students in an undergraduate emergency medical care programme

Background. Students may primarily use either a deep learning approach (DLA) or surface learning approach (SLA) in response to their perceptions of the intrinsic and extrinsic factors within a given  learning environment. By determining the learning approaches of students, one can provide important information on how they learn within an educational programme – information that can be used for various applications with regard to future structure and presentation of programme content.Objectives. To determine which learning approaches (DLA or SLA) were being used by students in the Bachelor of Emergency Medical Care programme at the University of Johannesburg, South Africa, in each academic year of study. Further objectives were to determine which intrinsic and extrinsic factors  influenced these choices and to assess whether learning approaches differed significantly between  academic years of study.Methods. This study was conducted using a quantitative design and a validated 20-question survey  instrument. Data analysis was primarily descriptive, but also focused on whether there was a significant difference in learning approaches between the four years of study.Results. Seventy students participated in the study, giving an overall response rate of 85%. Results showed that most students predominantly used a DLA, and that there was no significant difference between the four academic years of study with regard to the predominant learning approach. More students appeared to be influenced to use a DLA by extrinsic factors than intrinsic factors.Conclusion. Further research is needed to determine why students choose SLAs or DLAs, and the  influence of the educational environment on this process