Towards a scalable quantum computer/simulator based on trapped ions

We describe the concept and experimental demonstration of the basic building blocks of a scalable quantum computer using trapped-ion qubits. The trap structure is divided into subregions where ion qubits can either be held as memory or subjected to individual rotations and multi-qubit gates in processor zones. Thus, ion qubits can become entangled in one trapping zone, then separated and distributed to separate zones (by switching control-electrode potentials) where subsequent single- and two-ion gates, and/or detection is performed. Recent work using these building blocks includes (1) demonstration of a dense-coding protocol, (2) demonstration of enhanced qubit-detection efficiency using quantum logic, (3) generation of GHZ states and their application to enhanced precision in spectroscopy, and (4) the realization of teleportation with atomic qubits. In the final section an analog quantum computer that could provide a shortcut towards quantum simulations under requirements less demanding than those for a universal quantum computer is also described. PACS 03.67.Lx; 32.80.Qk     

ITQ-12: a new microporous silica polymorph potentially useful for light hydrocarbon separations

The new synthetic form of microporous crystalline silica, denoted as ITQ-12, shows a high potential for the separation of propane and propene from its mixtures.     

Synthesis of functionalized sulfonamides via 1,3-dipolar cycloaddition of pentafluorophenyl vinylsulfonate

[reaction: see text] An efficient intermolecular 1,3-dipolar cycloaddition of a variety of nitrones to pentafluorophenyl (PFP) vinylsulfonate is described. The transformation produces stable "reversed" cycloadducts of unprecedented stereo- and regioselectivity. Subsequent amine displacement of the PFP moiety furnished functionalized sulfonamide products in good yields.     

Spectroscopic evidence for the localization of Skyrmions near nu = 1 as T --> 0

Optically pumped nuclear magnetic resonance measurements of 71Ga spectra were carried out in an n-doped GaAs/Al(0.1)Ga0.9As multiple quantum well sample near the integer quantum Hall ground state nu = 1. As the temperature is lowered (down to T approximately 0.3 K), a "tilted plateau" emerges in the Knight shift data, which is a novel experimental signature of quasiparticle localization. The dependence of the spectra on both T and nu suggests that the localization is a collective process. The frozen limit spectra appear to rule out a 2D lattice of conventional Skyrmions.     

Reflection anisotropy spectroscopy: A new probe for the solid-liquid interface

Introducing reflection anisotropy spectroscopy (RAS) as a new probe for solid-liquid interfaces, we present results for the Au(110)/electrolyte interface which serves as a model system. We demonstrate that RAS is sensitive to surface phase transitions, step morphology, and electronic surface states. Using an empirical approach, the RA spectra are reproduced and features are identified which reflect the known character of the bias voltage driven (2x1) to (1x1) phase transition. RAS is established as an experimental technique to probe the electronic structure of solid-liquid interfaces in real time to study a wide range of interface properties.     

Energy-filtered XPEEM with NanoESCA using synchrotron and laboratory X-ray sources: Principles and first demonstrated results

The importance of energy filtering in PEEM-based imaging methods has been shown in recent years with the availability of powerful instruments. A new instrument, the NanoESCA, combines a fully electrostatic PEEM column and an aberration corrected double hemispherical analyser as energy filter. This paper reports on recently demonstrated XPEEM results using the first commercially available NanoESCA instrument operated with both synchrotron soft X-rays and monochromatic laboratory Al Kα radiation. The implementation of elemental and bonding-state specific imaging is shown with both excitation sources. The presently achieved (but not yet ultimate) lateral resolutions on energy filtered core-level images are 150 nm with a large synchrotron spot and below 1 μm with a focused laboratory source. To date this is the unique example of laboratory XPEEM core-level imaging.     

Fibrous twists and turns: early ceramic technology revealed through computed tomography

While the emergence of pottery manufacturing is a wide-spread historical occurrence, and one that has garnered the attention of archaeologists for decades, we know very little about how these ancient vessels were created. Through the application of radiographic scanning and computed tomography this paper provides insights into the manufacturing techniques used by the earliest potters in North America. While x-rays have been used to investigate ceramic manufacturing techniques for decades, this paper provides a reassessment of radiography in light of advances in both computed tomography and reconstructive software.     

Even-aged restrictions with sub-graph adjacency

Restrictions on the size and proximity of clearcuts have led to the development of a variety of exact and heuristic methods to optimize the net present value of timber harvests, subject to adjacency constraints. Most treat harvest units as pre-defined, and impose adjacency constraints on any two units sharing a common border. By using graph theory notation to define sub-graph adjacency constraints, opening size can be considered variable, which may be more appropriate for landscape-level planning. A small example data set is used in this paper to demonstrate the difference between the two types of adjacency constraints for both integer programming and heuristic solution methods.