Six-coordinate organotin(IV) complexes formed using the Kläui ligands; [CpCo{P(OR′)2O}3]SnR3 − nCln

The complexes [CpCo{P(OR′)2O}3]SnR3 − nCln [R′ = Me, Et; R = Ph, Me] are readily prepared from the corresponding organotin chloride and the sodium salt of the Kläui ligands. The X-ray crystal structures of the full series are reported for R = Ph, n = 0-3, and these show that they are all six-coordinate, including the Ph3Sn derivative which is the first example of a SnC3O3 coordination sphere. 1H, 13C, 31P and 119Sn NMR spectra are reported, and interpreted in terms of significant second-order effects and fluxional processes

The role of entanglement in dynamical evolution

Entanglement or entanglement generating interactions permit to achieve the maximum allowed speed in the dynamical evolution of a composite system, when the energy resources are distributed among subsystems. The cases of pre-existing entanglement and of entanglement-building interactions are separately addressed. The role of classical correlations is also discussed.Comment: 5 pages, 1 figure. Revised versio

Novel six-coordinate Aryl- and Alkyltin complexes

Organo-tin compounds have wide applications as pesticides and as intermediates for organic synthesis.¹ They are invariably Sn(IV) derivatives and are generally four-coordinate.² The mixed organo/chioro compounds of the type RnSnCI4-n do however have the ability to expand their coordination numbers to five or six. This depends critically on the substituents - with four organic groups, R₄Sn, there is no tendency at all to coordinate extra ligands, while at the other extreme SnCl₄ readily forms six-coordinate [SnC1₄L₂] complexes since the electronegative halo groups increase the Lewis acidity of the tin centre

Speedup of quantum state transfer by three- qubit interactions: Implementation by nuclear magnetic resonance

Universal quantum information processing requires single-qubit rotations and two-qubit interactions as minimal resources. A possible step beyond this minimal scheme is the use of three-qubit interactions. We consider such three-qubit interactions and show how they can reduce the time required for a quantum state transfer in an XY spin chain. For the experimental implementation, we use liquid-state nuclear magnetic resonance (NMR), where three-qubit interactions can be implemented by sequences of radio-frequency pulses.Comment: Comments are welcome to [email protected] or [email protected]. More experimental results are adde

Ground-layer wavefront reconstruction from multiple natural guide stars

Observational tests of ground layer wavefront recovery have been made in open loop using a constellation of four natural guide stars at the 1.55 m Kuiper telescope in Arizona. Such tests explore the effectiveness of wide-field seeing improvement by correction of low-lying atmospheric turbulence with ground-layer adaptive optics (GLAO). The wavefronts from the four stars were measured simultaneously on a Shack-Hartmann wavefront sensor (WFS). The WFS placed a 5 x 5 array of square subapertures across the pupil of the telescope, allowing for wavefront reconstruction up to the fifth radial Zernike order. We find that the wavefront aberration in each star can be roughly halved by subtracting the average of the wavefronts from the other three stars. Wavefront correction on this basis leads to a reduction in width of the seeing-limited stellar image by up to a factor of 3, with image sharpening effective from the visible to near infrared wavelengths over a field of at least 2 arc minutes. We conclude that GLAO correction will be a valuable tool that can increase resolution and spectrographic throughput across a broad range of seeing-limited observations.Comment: 25 pages, 8 figures, to be published in Astrophys.

Quantum computation over continuous variables

This paper provides necessary and sufficient conditions for constructing a universal quantum computer over continuous variables. As an example, it is shown how a universal quantum computer for the amplitudes of the electromagnetic field might be constructed using simple linear devices such as beam-splitters and phase shifters, together with squeezers and nonlinear devices such as Kerr-effect fibers and atoms in optical cavities. Such a device could in principle perform `quantum floating point' computations. Problems of noise, finite precision, and error correction are discussed.Comment: 9 pages, Te

Implementation of the Crisis Resolution Team model in adult mental health settings: a systematic review.

Crisis Resolution Teams (CRTs) aim to offer an alternative to hospital admission during mental health crises, providing rapid assessment, home treatment, and facilitation of early discharge from hospital. CRTs were implemented nationally in England following the NHS Plan of 2000. Single centre studies suggest CRTs can reduce hospital admissions and increase service users' satisfaction: however, there is also evidence that model implementation and outcomes vary considerably. Evidence on crucial characteristics of effective CRTs is needed to allow team functioning to be optimised. This review aims to establish what evidence, if any, is available regarding the characteristics of effective and acceptable CRTs

Cyclic networks of quantum gates

In this article initial steps in an analysis of cyclic networks of quantum logic gates is given. Cyclic networks are those in which the qubit lines are loops. Here we have studied one and two qubit systems plus two qubit cyclic systems connected to another qubit on an acyclic line. The analysis includes the group classification of networks and studies of the dynamics of the qubits in the cyclic network and of the perturbation effects of an acyclic qubit acting on a cyclic network. This is followed by a discussion of quantum algorithms and quantum information processing with cyclic networks of quantum gates, and a novel implementation of a cyclic network quantum memory. Quantum sensors via cyclic networks are also discussed.Comment: 14 pages including 11 figures, References adde