Two-parameter Hong-Ou-Mandel dip

A modification of the standard Hong-Ou-Mandel interferometer is proposed which allows one to replicate the celebrated coincidence dip in the case of two-independent delay parameters. In the ideal case where such delays are sufficiently stable with respect to the mean wavelength of the pump source, properly symmetrized input bi-photon states allow one to pinpoint their values through the identification of a zero in the coincidence counts, a feature that cannot be simulated by semiclassical inputs having the same spectral properties. Besides, in the presence of fluctuating parameters the zero in the coincidences is washed away: still the bi-photon state permits to recover the values of parameters with a visibility which is higher than the one allowed by semiclassical sources. The detrimental role of loss and dispersion is also analyzed and an application in the context of quantum positioning is presented.Comment: 16 pages,9 figure

Learning Discriminative Stein Kernel for SPD Matrices and Its Applications

Stein kernel has recently shown promising performance on classifying images represented by symmetric positive definite (SPD) matrices. It evaluates the similarity between two SPD matrices through their eigenvalues. In this paper, we argue that directly using the original eigenvalues may be problematic because: i) Eigenvalue estimation becomes biased when the number of samples is inadequate, which may lead to unreliable kernel evaluation; ii) More importantly, eigenvalues only reflect the property of an individual SPD matrix. They are not necessarily optimal for computing Stein kernel when the goal is to discriminate different sets of SPD matrices. To address the two issues in one shot, we propose a discriminative Stein kernel, in which an extra parameter vector is defined to adjust the eigenvalues of the input SPD matrices. The optimal parameter values are sought by optimizing a proxy of classification performance. To show the generality of the proposed method, three different kernel learning criteria that are commonly used in the literature are employed respectively as a proxy. A comprehensive experimental study is conducted on a variety of image classification tasks to compare our proposed discriminative Stein kernel with the original Stein kernel and other commonly used methods for evaluating the similarity between SPD matrices. The experimental results demonstrate that, the discriminative Stein kernel can attain greater discrimination and better align with classification tasks by altering the eigenvalues. This makes it produce higher classification performance than the original Stein kernel and other commonly used methods.Comment: 13 page

Deep-subwavelength features of photonic skyrmions in a confined electromagnetic field with orbital angular momentum

In magnetic materials, skyrmions are nanoscale regions where the orientation of electron spin changes in a vortex-type manner. Here we show that spin-orbit coupling in a focused vector beam results in a skyrmion-like photonic spin distribution of the excited waveguided fields. While diffraction limits the spatial size of intensity distributions, the direction of the field, defining photonic spin, is not subject to this limitation. We demonstrate that the skyrmion spin structure varies on the deep-subwavelength scales down to 1/60 of light wavelength, which corresponds to about 10 nanometre lengthscale. The application of photonic skyrmions may range from high-resolution imaging and precision metrology to quantum technologies and data storage where the spin structure of the field, not its intensity, can be applied to achieve deep-subwavelength optical patterns

The Qian painterly voice

My research explores my Chinese background experiences of immigration to Australia within the visual domain of Ba-Gua energies dialoguing with selected European painterly influences (especially Jenny Saville) related to Australia, painterly and new ink tradition methods, contemporary Chinese and Chinese-Australian painting unified by Ba-Gua spiritual ideas, through a methodology utilizing impasto and line informed by Chinese and European Romantic opera, all expressed within a contemporary version of Yan Li-ben’s emperor imagery, especially related to Qian or heaven. In this work and others in the folio, I use Chinese Ba-Gua (Qian) and Confucian philosophy to explore Chinese and Western artistic influences and Ba-Gua energies dialoguing with Chinese-Australian visual influences and Peking Opera and contemporary Australian music. I explored the artistic influences that have contributed to the extended sensation or synaesthesia of my painting across the tactile, sonic and optical fields. I drew across sources from ancient Chinese Emperor paintings and ink tradition alongside contemporary British and Australian layered paint and anatomical techniques, as well as draw from Renaissance masters. In addition, this research explores the contemporary themes, which have also influenced my work including intercultural contemporary Australian music. The originality of this approach in my cultural artistic fusion is that the Daoist-like movement of spirit and body (Chou, “Wenren and Culture”2004), expressed within Ba-Gua philosophy, becomes a kinetic unifying factor across a Chinese multi-artform practice. My creative folio included paintings and films which provide evidences for an analysis of both the common point of visual dialogue and cultural realities within these Chinese-Australian confluences towards expression of my artistic identity or voice, which I describe as Qian ‘painterly voice’. This ‘painterly voice’ has five main areas of investigation: firstly, English painter Jenny Saville’s intersection of painterly impasto and Chinese calligraphical line; secondly, the techniques of impasto and line related to Peking opera and Italian lyric opera; thirdly, ancient Chinese painter Yan Li-pen’s iconic emperor series extended to Australia; fourthly, the intersections of the Chinese multi-artform practice where calligraphically line, watercolour suggestiveness, and painterly impasto layering work as synergies and counterpoints to contemporary Australian composition within several music-theatre works; and finally, Ba-Gua ideas into contemporary Chinese artistic ideas in China (Qian and family order within Zhang Xiaogang) and Australia (Chinese-Australian Lindy Lee’s exploration of Zen Buddhism). Ultimately, this research examines how each of these factors culminates in my own personal philosophy and Qian ‘painterly voice’

Phase investigation of zirconia fibers and their applications on solid oxide fuel cells (SOFCs)

Pure zirconia nanofibers were fabricated by electrospinning zirconia-polymer precursor and subsequent annealing. Fiber properties such as polymer decomposition, crystallization formation, phase transformation, surface morphologies, etc., were investigated by various techniques, including thermogravimetric analysis (TGA) and differential thermal analysis (DTA), high temperature differential scanning calorimeter (HTDSC), powder X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), etc. It was found the crystallization of as-spun fibers started at 450 °C and the initial crystallized zirconia phase was tetragonal (t), which began transforming to monoclinic (m) phase at 650 °C as evidenced by XRD; HTDSC showed at different thermal circles, the m-to-t transformation temperatures remained virtually unchanged while the reverse t-to-m temperatures systematically shifted from 924.9 to 978.6 °C as the progress of thermal circles; FESEM examinations revealed that fibers calcined to 1000 °C went through thermal grooving due to surface diffusion during heat treatment; fibers heated to 1370 °C formed the so-called “bamboo wires”, where volume diffusion was the dominant driving force. A novel route to fabricate nanofiber-based anodes for solid oxide fuel cells (SOFCs) was also presented. Uniform YSZ nanofibers were first synthesized by electrospinning of 8YSZ dispersion. The fiber surfaces were then electrolessly plated with a layer of Ni after sintering. The Ni-YSZ nanofibers were slurry-coated on a commercial half cell as the anode and the cell performance was tested; the Ni content was quantified by XPS. A second cell with the same Ni content in the anode as the first one, prepared by conventional ball-milling of powders, was also fabricated and tested. We found the peak power density for the cell with the fiber-based anode is twice of that with the powder-based anode; the FESEM images of the two cells showed that the fiber-coated anode mainly consisted of nanofibers, which formed an interconnected network within the anode; on the other hand, the particles in the powder-coated anode formed sphere-like granules that are unorganized and are not well-connected, which will not be advantageous for anode functionality. In the end we came up with two anode models that are based on FESEM observations and they explained the superiority of the fiber-based anode