Quantum Computing with an 'Always On' Heisenberg Interaction

Many promising ideas for quantum computing demand the experimental ability to directly switch 'on' and 'off' a physical coupling between the component qubits. This is typically the key difficulty in implementation, and precludes quantum computation in generic solid state systems, where interactions between the constituents are 'always on'. Here we show that quantum computation is possible in strongly coupled (Heisenberg) systems even when the interaction cannot be controlled. The modest ability of 'tuning' the transition energies of individual qubits proves to be sufficient, with a suitable encoding of the logical qubits, to generate universal quantum gates. Furthermore, by tuning the qubits collectively we provide a scheme with exceptional experimental simplicity: computations are controlled via a single 'switch' of only six settings. Our schemes are applicable to a wide range of physical implementations, from excitons and spins in quantum dots through to bulk magnets.Comment: 4 pages, 3 figs, 2 column format. To appear in PR

A quantum mechanical model of the upper bounds of the cascading contribution to the second hyperpolarizability

Microscopic cascading of second-order nonlinearities between two molecules has been proposed to yield an enhanced third-order molecular nonlinear-optical response. In this contribution, we investigate the two-molecule cascaded second hyperpolarizability and show that it will never exceed the fundamental limit of a single molecule with the same number of electrons as the two-molecule system. We show the apparent divergence behavior of the cascading contribution to the second hyperpolarizability vanishes when properly taking into account the intermolecular interactions. Although cascading can never lead to a larger nonlinear-optical response than a single molecule, it provides alternative molecular design configurations for creating materials with large third-order susceptibilities that may be difficult to design into a single molecule.Comment: 13 pages, 9 figures, 1 tabl

Single-qubit unitary gates by graph scattering

We consider the effects of plane-wave states scattering off finite graphs, as an approach to implementing single-qubit unitary operations within the continuous-time quantum walk framework of universal quantum computation. Four semi-infinite tails are attached at arbitrary points of a given graph, representing the input and output registers of a single qubit. For a range of momentum eigenstates, we enumerate all of the graphs with up to $n=9$ vertices for which the scattering implements a single-qubit gate. As $n$ increases, the number of new unitary operations increases exponentially, and for $n>6$ the majority correspond to rotations about axes distributed roughly uniformly across the Bloch sphere. Rotations by both rational and irrational multiples of $\pi$ are found.Comment: 8 pages, 7 figure

Tunable-focus liquid lens controlled using a servo motor

We demonstrated a liquid lens whose focal length can be controlled by a servo motor. The lens cell is composed of elastic membrane, planar glass plate, a periphery sealing ring, and a liquid with a fixed volume in the lens chamber. Part of the periphery sealing ring is excavated to form a hollow chamber which functions as a reservoir. This hollowed periphery is surrounded by an exterior rubber membrane. The arm of a servo motor is used to deform the elastic rubber. Squeezing the liquid contained in the reservoir into the lens chamber. Excess liquid in the lens chamber will push the lens membrane to outward, resulting in a lens shape change. Due to the compact structure and easy operation, this liquid lens has potential applications in zoom lenses, auto beam steering, and eyeglasses

Influenza A Virus Host Shutoff Disables Antiviral Stress-Induced Translation Arrest

Influenza A virus (IAV) polymerase complexes function in the nucleus of infected cells, generating mRNAs that bear 5′ caps and poly(A) tails, and which are exported to the cytoplasm and translated by host machinery. Host antiviral defences include mechanisms that detect the stress of virus infection and arrest cap-dependent mRNA translation, which normally results in the formation of cytoplasmic aggregates of translationally stalled mRNA-protein complexes known as stress granules (SGs). It remains unclear how IAV ensures preferential translation of viral gene products while evading stress-induced translation arrest. Here, we demonstrate that at early stages of infection both viral and host mRNAs are sensitive to drug-induced translation arrest and SG formation. By contrast, at later stages of infection, IAV becomes partially resistant to stress-induced translation arrest, thereby maintaining ongoing translation of viral gene products. To this end, the virus deploys multiple proteins that block stress-induced SG formation: 1) non-structural protein 1 (NS1) inactivates the antiviral double-stranded RNA (dsRNA)-activated kinase PKR, thereby preventing eIF2α phosphorylation and SG formation; 2) nucleoprotein (NP) inhibits SG formation without affecting eIF2α phosphorylation; 3) host-shutoff protein polymerase-acidic protein-X (PA-X) strongly inhibits SG formation concomitant with dramatic depletion of cytoplasmic poly(A) RNA and nuclear accumulation of poly(A)-binding protein. Recombinant viruses with disrupted PA-X host shutoff function fail to effectively inhibit stress-induced SG formation. The existence of three distinct mechanisms of IAV-mediated SG blockade reveals the magnitude of the threat of stress-induced translation arrest during viral replication

Survival and Spatial Ecology of the Snapping Turtle, Chelydra serpentina, on the Upper Mississippi River

We studied the survival and spatial ecology of adult Snapping Turtles (Chelydra serpentina) on Pool 8 of the Upper Mississippi River (UMR) during 1997-2001. We captured 597 Snapping Turtles 745 times (333 adult males; 238 adult females; and 26 juveniles) at two study sites; Goose Island, Wisconsin and Lawrence Lake, Minnesota. From this sample, we radio-marked 104 Snapping Turtles of legal harvest size 128 times. Annual survival ranged from 0.857 to 1.000 and averaged 0.944 with Goose Island and Lawrence Lake estimates pooled. Legal harvest was the most important cause of mortality and accounted for 57% of documented deaths. Annual home range size using the Poly-Buff (PB) method averaged 11.13 ha and ranged from 2.20 ha to 37.18 ha. Emergent and rooted-floating aquatic vegetation were used disproportionally more than their availability and 72% of all locations collected during the active period occurred within these habitat types. Overall, radio-marked Snapping Turtles selected hibernacula in the following habitat categories; marshes (38%), main/side channels (28%), backwater sloughs and small ponds (14%), spring areas (10%), small tributary streams (7%), and tertiary channels (3%). Developing conservative, consistent harvest regulations among the states that border the UMR should be a management priority

Interactional positioning and narrative self-construction in the first session of psychodynamic-interpersonal psychotherapy

The purpose of this study is to identify possible session one indicators of end of treatment psychotherapy outcome using the framework of three types of interactional positioning; client’s self-positioning, client’s positioning between narrated self and different partners, and the positioning between client and therapist. Three successful cases of 8-session psychodynamic-interpersonal (PI) therapy were selected on the basis of client Beck Depression Inventory scores. One unsuccessful case was also selected against which identified patterns could be tested. The successful clients were more descriptive about their problems and demonstrated active rapport-building, while the therapist used positionings expressed by the client in order to explore the positionings developed between them during therapy. The unsuccessful case was characterized by lack of positive self-comment, minimization of agentic self-capacity, and empathy-disrupting narrative confusions. We conclude that the theory of interactional positioning has been useful in identifying patterns worth exploring as early indicators of success in PI therapy

Medical Evaluation and Triage of the Agitated Patient: Consensus Statement of the American Association for Emergency Psychiatry Project BETA Medical Evaluation Workgroup

Numerous medical and psychiatric conditions can cause agitation; some of these causes are life threatening. It is important to be able to differentiate between medical and nonmedical causes of agitation so that patients can receive appropriate and timely treatment. This article aims to educate all clinicians in nonmedical settings, such as mental health clinics, and medical settings on the differing levels of severity in agitation, basic triage, use of de-escalation, and factors, symptoms, and signs in determining whether a medical etiology is likely. Lastly, this article focuses on the medical workup of agitation when a medical etiology is suspected or when etiology is unclear

Fantasies of subjugation: a discourse theoretical account of British policy on the European Union

The decision by the UK government to hold a referendum on Britain’s membership of the European Union (EU) marks an important development in policy towards the EU. Policy changes of this kind must be understood in the historical and political context in which they occur. This includes the framing of the policy issues within public discourse. In the UK, policies are formed in a discursive environment which is overwhelmingly hostile towards the EU. Debates are structured by a predominantly Euroskeptic discourse which emphasizes the UK’s separation and heterogeneity from the rest of the EU. Drawing on the logics of critical explanation, this article examines the structure and affective power of Euroskeptic discourses which dictate the terms of the EU debate. It presents a case study of the recent EU treaty revision process, culminating in the Treaty of Lisbon. In so doing, it enables a deeper understanding of recent policy developments