http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18348 25 page(s) 2012-03-29T21:22:32.940Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18325 We study the single particle dynamics of a mobile non-Abelian anyon hopping around many pinned anyons on a surface, by modeling it with a discrete time quantum walk. During the evolution, the spatial degree of freedom of the mobile anyon becomes entangled with the fusion degrees of freedom of the collective system. Each quantum trajectory makes a closed braid on the world lines of the particles establishing a direct connection between statistical dynamics and quantum link invariants. We find that asymptotically a mobile Ising model anyon becomes so entangled with its environment that its statistical dynamics reduces to a classical random walk with linear dispersion in contrast to particles with Abelian statistics which have quadratic dispersion. 2012-03-26T16:00:24.483Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:14341 We show how trajectories can be reintroduced in quantum mechanics provided that its spatial continuum is modelled by a variable real number (qr-number) continuum. Such a continuum can be constructed using only standard Hilbert space entities. In this approach, the geometry of atoms and subatomic objects differs from that of classical objects. The systems that are non-local when measured in the classical space-time continuum may be localized in the quantum continuum. We compare trajectories in this new description of space-time with the corresponding Bohmian picture. 2011-08-06T02:41:23.886Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13689 Large-scale quantum information processing and distributed quantum computation require the ability to perform entangling operations on a large number of qubits. We describe a new photonic module which prepares, deterministically, photonic cluster states using an atom in a cavity as an ancilla. Based on this module, we design a network for constructing 2D cluster states and then we extend the architecture to 3D topological cluster states. Advantages of our design include a passive switching mechanism and the possibility of using global control pulses for the atoms in the cavity. The architecture described here is well-suited for integrated photonic circuits on a chip and could be used as a basis of a future quantum optical processor or in a quantum repeater node. 2011-06-20T12:51:30.156Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13460 Microfluidic particle separation arrays are capable of passive sorting of microparticles or cells by size while avoiding blockage. Despite the usefulness of boundaries for concentration and parallel integration of arrays, separation efficiency is severely degraded in the areas adjacent to the boundaries due to the aberrant fluid flow found there. This letter shows how to eliminate this problem by modifying the boundary interface. At each row the boundary is moved by a specific amount to ensure a linear change in flux from row to row, which leads to uniform flow patterns and improved separation characteristics throughout the array. 2011-06-02T06:10:30.482Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13202 We report structural and electronic properties of epitaxial hafnium nitride films grown on MgO by plasma-assisted pulsed laser deposition. The electronic structure measured using soft x-ray absorption and emission spectroscopy is in excellent agreement with the results of a band structure calculation. We show that by varying the growth conditions we can extend the films’ reflectance further toward the UV, and we relate this observation to the electronic structure. 2011-05-25T21:44:01.151Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12493 Single-spin measurements on the ground state of an interacting spin lattice can be used to perform a quantum computation. We show how such measurements can mimic renormalization group transformations and remove the short-ranged variations of the state that can reduce the fidelity of a computation. This suggests that the quantum computational ability of a spin lattice could be a robust property of a quantum phase. We illustrate our idea with the ground state of a rotationally invariant spin-1 chain, which can serve as a quantum computational wire not only at the Affleck-Kennedy-Lieb-Tasaki point, but within the Haldane phase. 2011-04-08T07:01:09.697Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12496 We propose a novel deterministic protocol, based on continuous light flows, that enables us to control the concentration of light in generic plasmonic nanostructures. Based on an exact inversion of the response tensor of the nanosystem, the so-called deterministic optical inversion protocol provides a physical solution for the incident field leading to a desired near-field pattern, expressed in the form of a coherent superposition of high-order beams. We demonstrate the high degree of control achieved on complex plasmonic architectures and quantify its efficiency and accuracy. 2011-04-08T07:00:59.176Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12489 It is not so well known that measurement-free quantum error correction protocols can be designed to achieve fault-tolerant quantum computing. Despite their potential advantages in terms of the relaxation of accuracy, speed, and addressing requirements, they have usually been overlooked since they are expected to yield a very bad threshold. We show that this is not the case. We design fault-tolerant circuits for the 9-qubit Bacon-Shor code and find an error threshold for unitary gates and preparation of p(p,g)thresh=3.76×10⁻⁵ (30% of the best known result for the same code using measurement) while admitting up to 1/3 error rates for measurements and allocating no constraints on measurement speed. We further show that demanding gate error rates sufficiently below the threshold pushes the preparation threshold up to p(p)thresh=1/3. 2011-04-07T06:10:20.921Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12307 Atomic force microscopy (AFM) study is used to measure the surface topology and roughness of radial and capture spider silks on the micro- and nanoscale. This is done for silks of the orb weaver spider Argiope keyserlingi. Capture silk has a surface roughness that is five times less than that for radial silk. The capture silk has an equivalent flatness of λ/100 (5–6 nm deep surface features) as an optical surface. This is equivalent to a very highly polished optical surface. AFM does show the number of silk fibers that make up a silk thread but geometric distortion occurs during sample preparation. This prevented AFM from accurately measuring the silk topology on the microscale in this study. 2011-03-24T13:20:48.381Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12225 We present a system for modeling disfluency in conversational speech: repairs, fillers, and self-interruption points (IPs). For each sentence, candidate repair analyses are generated by a stochastic tree adjoining grammar (TAG) noisy-channel model. A probabilistic syntactic language model scores the fluency of each analysis, and a maximum-entropy model selects the most likely analysis given the language model score and other features. Fillers are detected independently via a small set of deterministic rules, and IPs are detected by combining the output of repair and filler detection modules. In the recent Rich Transcription Fall 2004 (RT-04F) blind evaluation, systems competed to detect these three forms of disfluency under two input conditions: a best-case scenario of manually transcribed words and a fully automatic case of automatic speech recognition (ASR) output. For all three tasks and on both types of input, our system was the top performer in the evaluation. 2011-03-21T05:01:53.735Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11646 The electronic structure of GdN films grown by pulsed laser deposition has been investigated by soft x-ray absorption (XAS) and x-ray emission spectroscopy (XES) at the N K-edge. Density functional calculations within the local spin density approximation with Hubbard-U corrections of the N p weighted bands and density of states are used to extract band information from the spectra. Gd M₄,₅ XAS and XES spectra are also presented. The XES-XAS separation is shown to give information on the f-band spin splitting and the XAS line shapes are shown to reflect atomic multiplet effects. 2011-02-04T08:20:10.414Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11640 Many proposals for fault tolerant quantum computation (FTQC) suffer detectable loss processes. Here we show that topological FTQC schemes, which are known to have high error thresholds, are also extremely robust against losses. We demonstrate that these schemes tolerate loss rates up to 24.9%, determined by bond percolation on a cubic lattice. Our numerical results show that these schemes retain good performance when loss and computational errors are simultaneously present. 2011-02-04T05:20:35.520Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9759 We have characterised a small, high-efficiency diesel generator selected to power remote experiments on the Antarctic plateau at altitudes of up to 5000 m. We describe the design of an environmental chamber to simulate these high altitudes and present an experimental investigation of the engine operation at high altitude on Jet A-1, comparing this to the engine's performance at sea level. Although attention must be paid to the provision of adequate cooling, no modification to the engine itself is required. Our final system provides very high reliability and produces 1500 W of electrical power with a fuel consumption of 280 g kWh⁻¹. A bank of ultracapacitors is used to start the engine in the cold environment of Antarctica. We describe the low-temperature operation and survival tests that we performed on the ultracapacitors and the engine. 2010-10-15T10:11:52.568Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:8719 9 page(s) 2010-07-15T19:20:55.825Z ]]>