Adiabatic Rotation, Quantum Search and Preparation of Superposition States

We introduce the idea of using adiabatic rotation to generate superpositions of a large class of quantum states. For quantum computing this is an interesting alternative to the well-studied "straight line" adiabatic evolution. In ways that complement recent results, we show how to efficiently prepare three types of states: Kitaev's toric code state, the cluster state of the measurement-based computation model and the history state used in the adiabatic simulation of quantum circuit. We also show that the method, when adapted for quantum search, provides quadratic speedup as other optimal methods do with the advantages that the problem Hamiltonian is time-independent and that the energy gap above the ground state is strictly nondecreasing with time. Likewise the method can be used for optimization as an alternative to the usual adiabatic algorithm.Comment: Expanded to 6 pages; Accepted by Phys. Rev.

Towards the Green-Griffiths-Lang conjecture

The Green-Griffiths-Lang conjecture stipulates that for every projective variety X of general type over C, there exists a proper algebraic subvariety of X containing all non constant entire curves f : C $\rightarrow$ X. Using the formalism of directed varieties, we prove here that this assertion holds true in case X satisfies a strong general type condition that is related to a certain jet-semistability property of the tangent bundle TX . We then give a sufficient criterion for the Kobayashi hyperbolicity of an arbitrary directed variety (X,V). This work is dedicated to the memory of Professor Salah Baouendi.Comment: version 2 has been expanded and improved (15 pages

Bootstrap Approximations in Contractor Renormalization

We propose a bootstrap method for approximating the long-range terms in the Contractor Renormalization (CORE) method. The idea is tested on the 2-D Heisenberg antiferromagnet and the frustrated J_2-J_1 model. We obtain renormalization group flows that directly reveal the Neel phase of the unfrustrated HAF and the existence of a phase transition in the J_2-J_1 model for weak frustration. However, we find that this bootstrap method is dependent on blocking and truncation schemes. For this reason, we discuss these dependencies and unresolved issues that researchers who use this approach must consider.Comment: Some clarifications added for Phys Rev submissio

A robust model generation technique for model-based video coding

Centre for Multimedia Signal Processing, Department of Electronic and Information Engineering2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Relative motion at the bone-prosthesis interface

Bone ingrowth in porous surfaces of human joint implants is a desired condition for long-term fixation in patients who are physically active (such as in sport or work). It is generally recognized that little actual bone ingrowth occurs. The best clinical results report between 10 and 20% of the total prosthetic surface in contact with bone will feature good bone ingrowth. One inhibiting factor is the relative motion of the bone with respect to the implant during load-bearing. This study investigated mathematically the interface micromotion (transverse reversible relative motion) between a flat metal tibial prosthetic surface of a prototype implant, and the bone at the resection site. The aim was to assess the effect of perimeter fixation versus midcondylar pin fixation and the effect of plate thickness and plate stiffness.\ud \ud Results showed that in the prototype design the largest reversible relative bone motion occurred at the tibial eminence. By design, the skirt fixation at the perimeter would prevent bone motion. A PCA (Howmedica Inc.) prosthesis has been widely used clinically and was chosen for a control because its fixation by two pegs beneath the condyles is a common variation on the general design of a relatively thick and stiff metal tibial support tray with pegs in each condylar area. The PCA tibial prosthesis showed the largest bone motion at the perimeter along the midcondylar mediolateral line, while being zero at the pegs. Maximum relative bone motion for the prototype was 37 ¿m and for the control was 101 ¿m. Averaged values showed the prototype to have 38% of the relative reversible bone motion of the control (PCA)

From quantum circuits to adiabatic algorithms

This paper explores several aspects of the adiabatic quantum computation model. We first show a way that directly maps any arbitrary circuit in the standard quantum computing model to an adiabatic algorithm of the same depth. Specifically, we look for a smooth time-dependent Hamiltonian whose unique ground state slowly changes from the initial state of the circuit to its final state. Since this construction requires in general an n-local Hamiltonian, we will study whether approximation is possible using previous results on ground state entanglement and perturbation theory. Finally we will point out how the adiabatic model can be relaxed in various ways to allow for 2-local partially adiabatic algorithms as well as 2-local holonomic quantum algorithms.Comment: Version accepted by and to appear in Phys. Rev.

Extrapolated High-Order Propagators for Path Integral Monte Carlo Simulations

We present a new class of high-order imaginary time propagators for path-integral Monte Carlo simulations by subtracting lower order propagators. By requiring all terms of the extrapolated propagator be sampled uniformly, the subtraction only affects the potential part of the path integral. The negligible violation of positivity of the resulting path integral at small time steps has no discernable affect on the accuracy of our method. Thus in principle arbitrarily high order algorithms can be devised for path-integral Monte Carlo simulations. We verify this claim is by showing that fourth, sixth, and eighth order convergence can indeed be achieved in solving for the ground state of strongly interacting quantum many-body systems such as bulk liquid $^4$He.Comment: 9 pages and 3 figures. Submitted to J. Chem. Phy

Understanding Nurses\u27 Knowledge Work

Hospitals are increasingly investing in technologies and electronic knowledge management systems to improve patient care outcomes. Yet, effective implementation of these initiatives has been difficult with questionable return on investment outcomes (Ontario Hospital Association [OHA], 2007, 2008). Paton (2009) argues that understanding how employees put their knowledge into action at work is essential to successful knowledge management for organizations. Thus, strategies that target nurses’ knowledge work may be more effective for hospitals; particularly in times of mounting fiscal deficits and demands for health services. This study examined the behaviors, influences, and outcomes of nurses’ knowledge work. The hypothesized model was based on Kelloway & Barling’s (2000) knowledge work theory; explaining the impact of empowering leadership on nurses’ accountability, role-breadth self-efficacy, and control over practice to influence their knowledge work behaviours and ultimately, patient care delivery outcomes. The model was tested on a random sample of 318 registered nurses in Ontario, and initially demonstrated poor fit with the observed data; with further refinement to improve the overall model fit [χ2(df) = 512.66 (199), p \u3c .001, SRMR = .064, CFI = .91, RMSEA = .071]. Final model results suggest that empowering leadership practices increase nurses’ knowledge work behaviors, which subsequently enhances their care coordination activities and patient care quality. Empowering leadership specifically increases nurses’ knowledge work by positively influencing their accountability and role-breadth self-efficacy, but not control over practice. This study is among the first to identify the behaviors by which nurses’ demonstrate their knowledge work, and the process by which empowering leadership influences such work behaviors to improve patient care quality