5,843 research outputs found
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
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
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
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 (where 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
First Supramolecular Sensors for Phosphonate Anions
Fluorescent tripodal anion sensors with a 1,3,5-triethylbenzene core display a turn-on fluorescence response to phosphonate and phosphate anions and may be used as optical sensors. The properties of the receptors and sensors as well as their anion binding behavior were investigated both in solution and in solid state. The turn-on fluorescence response can be leveraged in sensing of phosphate anions and, most importantly, hydrolysis products of the nerve gas sarin, isopropyl methylphosphonate (IMP), and methylphosphonate (MP). The fluorescence signal amplification in the presence of anions allows for application of these molecules in a sensor microarray suitable for high-throughput screening.NSF CHE 0750303, EXP-LA 0731153BGSU (TIE Grant)Chemistr
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