Single hole transistor in a p-Si/SiGe quantum well

A single hole transistor is patterned in a p-Si/SiGe quantum well by applying voltages to nanostructured top gate electrodes. Gating is achieved by oxidizing the etched semiconductor surface and the mesa walls before evaporation of the top gates. Pronounced Coulomb blockade effects are observed at small coupling of the transistor island to source and drain.Comment: 3 pages, 3 figure

Universal quantum computing based on magnetic domain wall qubits

Quantum computers allow to solve efficiently certain problems that are intractable for classical computers. For the realization of a quantum computer, a qubit design as the basic building block is a nontrivial starting point. We propose the utilization of nanoscale magnetic domain walls, which are stabilized by achiral energy, as the building blocks for a universal quantum computer made of ferromagnetic racetracks. In contrast to the domain walls stabilized by conventional Dzyaloshinskii-Moriya interactions, these achiral domain walls are bistable and show two degenerate chirality forms. When the domain wall is extremely small, it can be viewed as a quantum mechanical object and the two degenerate chiralities of the domain walls can be used to encode the qubit states $\lvert 0 \rangle$ and $\lvert 1 \rangle$. We show that the single-qubit quantum gates are regulated by magnetic and electric fields, while the Ising exchange coupling facilitates the two-qubit gates. The integration of these quantum gates allows for a universal quantum computation. Our findings demonstrate a promising approach for achieving quantum computing through spin textures that exist in ferromagnetic materials.Comment: Submitted on August 7t

Topological phases with generalized global symmetries

We present simple lattice realizations of symmetry-protected topological (SPT) phases with $q$-form global symmetries where charged excitations have $q$ spatial dimensions. Specifically, we construct $d$ space-dimensional models supported on a $(d+1)$-colorable graph by using a family of unitary phase gates, known as multi-qubit control-$Z$ gates in quantum information community. In our construction, charged excitations of different dimensionality may coexist and form a short-range entangled state which is protected by symmetry operators of different dimensionality. Non-triviality of proposed models, in a sense of quantum circuit complexity, is confirmed by studying protected boundary modes, gauged models and corresponding gapped domain walls. We also comment on applications of our construction to quantum error-correcting codes, and discuss corresponding fault-tolerant logical gates.Comment: 32 pages, 17 figures, single column (v2, corrected minor mistakes and typos, to appear in PRB

We Need Gates

Educational contexts open to and self-directed by children promote learning, but traditional direct instruction also is appropriate in many areas. Gates, not walls, are what we need

CBCT Assessment of Root Dentine Removal by Gates-Glidden Drills and Two Engine-Driven Root Preparation Systems

Introduction: The aim of this study was to compare the dentine removing efficacy of Gates-Glidden drills with hand files, ProTaper and OneShape single-instrument system using cone-beam computed tomography (CBCT). Methods and Materials: A total of 39 extracted bifurcated maxillary first premolars were divided into 3 groups (n=13) and were prepared using either Gates-Glidden drills and hand instruments, ProTaper and OneShape systems. Pre- and post-instrumentation CBCT images were obtained. The dentin thickness of canals was measured at furcation, and 1 and 2 mm from the furcation area in buccal, palatal, mesial and distal walls. Data were analyzed using one-way ANOVA test. Tukey’s post hoc tests were used for two-by-two comparisons. Results: Gates-Glidden drills with hand files removed significantly more (P<0.001) dentine than the engine-driven systems in all canal walls (buccal, palatal, mesial and distal). There were no significant differences between OneShape and ProTaper rotary systems (P>0.05). Conclusion: The total cervical dentine removal during canal instrumentation was significantly less with engine-driven file systems compared to Gates-Glidden drills. There were no significant differences between residual dentine thicknesses left between the various canal walls.Keywords: Cone-Beam Computed Tomography; Maxillary First Premolar; Root Canal Preparation; Root Thicknes

Universal quantum computation on a semiconductor quantum wire network

Universal quantum computation (UQC) using Majorana fermions on a 2D topological superconducting (TS) medium remains an outstanding open problem. This is because the quantum gate set that can be generated by braiding of the Majorana fermions does not include \emph{any} two-qubit gate and also the single-qubit $\pi/8$ phase gate. In principle, it is possible to create these crucial extra gates using quantum interference of Majorana fermion currents. However, it is not clear if the motion of the various order parameter defects (vortices, domain walls, \emph{etc.}), to which the Majorana fermions are bound in a TS medium, can be quantum coherent. We show that these obstacles can be overcome using a semiconductor quantum wire network in the vicinity of an $s$-wave superconductor, by constructing topologically protected two-qubit gates and any arbitrary single-qubit phase gate in a topologically unprotected manner, which can be error corrected using magic state distillation. Thus our strategy, using a judicious combination of topologically protected and unprotected gate operations, realizes UQC on a quantum wire network with a remarkably high error threshold of $0.14$ as compared to $10^{-3}$ to $10^{-4}$ in ordinary unprotected quantum computation.Comment: 7 pages, 2 figure

Worker injuries involving the interaction of cattle, cattle handlers, and farm structures or equipment

Citation: Fox, S., Ricketts, M., & Minton, J. E. (2015). Worker injuries involving the interaction of cattle, cattle handlers, and farm structures or equipment. Journal of Agricultural Safety and Health, 21(1), 3-12. doi:10.13031/jash.21.10221Cattle have been identified as leading sources of injuries to agricultural workers. The present study focused on worker injuries that involved the interaction of cattle, cattle handlers, and farm structures or equipment. The goal of the study was to identify opportunities for injury prevention. We examined 221 reports of injury to cattle handlers from the Consumer Product Safety Commission's National Electronic Injury Surveillance System (NEISS). Expected interactions led to many of the cattle-handling injuries reported in the NEISS database. In almost 30% of cases, cattle pushed workers into structures such as fences, gates, posts, and walls. In another 16% to 19% of injuries, cattle struck gates and other objects, propelling them at the victims. The present research makes several important contributions to the study of cattle-handling injuries. First, the research supports an increased emphasis on the development of safer gate designs (e.g., gates that are remotely operated or that absorb energy to limit the speed at which they may be propelled by animals). Second, the research suggests a need for additional study of energy-absorbing fence and wall structures. We view these two points to be of significance because gates and associated structures (e.g., posts, fences, and walls) accounted for 45% of the injuries in the dataset, based on the associated injury narrative. Finally, the research identifies a previously unexplored source of agricultural injury data, namely the NEISS database. © 2015 ASABE

Reconfigurable magnetic logic based on the energetics of pinned domain walls

A magnetic logic concept based on magnetic switching in three stripe domains separated by pinned magnetic domain walls is proposed. The relation between the inputs and the output of the logic operator is determined by the energetics of the domain walls, which can be switched between two distinctive states by an external magnetic field. Together with magnetic read-out along two orthogonal directions, non-volatile AND, OR, NAND, and NOR gates can be created. The logic concept is experimentally demonstrated using CoFeB films on BaTiO3 substrates, and micromagnetic simulationsare used to analyze the energetics of the system.Peer reviewe