2,323 research outputs found
Asymptotically Optimal Quantum Circuits for d-level Systems
As a qubit is a two-level quantum system whose state space is spanned by |0>,
|1>, so a qudit is a d-level quantum system whose state space is spanned by
|0>,...,|d-1>. Quantum computation has stimulated much recent interest in
algorithms factoring unitary evolutions of an n-qubit state space into
component two-particle unitary evolutions. In the absence of symmetry, Shende,
Markov and Bullock use Sard's theorem to prove that at least C 4^n two-qubit
unitary evolutions are required, while Vartiainen, Moettoenen, and Salomaa
(VMS) use the QR matrix factorization and Gray codes in an optimal order
construction involving two-particle evolutions. In this work, we note that
Sard's theorem demands C d^{2n} two-qudit unitary evolutions to construct a
generic (symmetry-less) n-qudit evolution. However, the VMS result applied to
virtual-qubits only recovers optimal order in the case that d is a power of
two. We further construct a QR decomposition for d-multi-level quantum logics,
proving a sharp asymptotic of Theta(d^{2n}) two-qudit gates and thus closing
the complexity question for all d-level systems (d finite.) Gray codes are not
required, and the optimal Theta(d^{2n}) asymptotic also applies to gate
libraries where two-qudit interactions are restricted by a choice of certain
architectures.Comment: 18 pages, 5 figures (very detailed.) MatLab files for factoring qudit
unitary into gates in MATLAB directory of source arxiv format. v2: minor
change
Isobaric multiplet yrast energies and isospin non-conserving forces
The isovector and isotensor energy differences between yrast states of
isobaric multiplets in the lower half of the region are quantitatively
reproduced in a shell model context. The isospin non-conserving nuclear
interactions are found to be at least as important as the Coulomb potential.
Their isovector and isotensor channels are dominated by J=2 and J=0 pairing
terms, respectively. The results are sensitive to the radii of the states,
whose evolution along the yrast band can be accurately followed.Comment: 4 pages, 4 figures. Superseeds second part of nucl-th/010404
Time Reversal and n-qubit Canonical Decompositions
For n an even number of qubits and v a unitary evolution, a matrix
decomposition v=k1 a k2 of the unitary group is explicitly computable and
allows for study of the dynamics of the concurrence entanglement monotone. The
side factors k1 and k2 of this Concurrence Canonical Decomposition (CCD) are
concurrence symmetries, so the dynamics reduce to consideration of the a
factor. In this work, we provide an explicit numerical algorithm computing v=k1
a k2 for n odd. Further, in the odd case we lift the monotone to a two-argument
function, allowing for a theory of concurrence dynamics in odd qubits. The
generalization may also be studied using the CCD, leading again to maximal
concurrence capacity for most unitaries. The key technique is to consider the
spin-flip as a time reversal symmetry operator in Wigner's axiomatization; the
original CCD derivation may be restated entirely in terms of this time
reversal. En route, we observe a Kramers' nondegeneracy: the existence of a
nondegenerate eigenstate of any time reversal symmetric n-qubit Hamiltonian
demands (i) n even and (ii) maximal concurrence of said eigenstate. We provide
examples of how to apply this work to study the kinematics and dynamics of
entanglement in spin chain Hamiltonians.Comment: 20 pages, 3 figures; v2 (17pp.): major revision, new abstract,
introduction, expanded bibliograph
The introduction and refinement of the assessment of digitally recorded audio presentations
This case study critically evaluates benefits and challenges of a form of assessment included in a final year undergraduate Religious Studies Open University module, which combines a written essay task with a digital audio recording of a short oral presentation. Based on the
analysis of student and tutor feedback and sample assignments, this study critically examines how teaching and learning practices linked to this novel form of assessment have been iteratively developed in
light of the project findings over a period of two years. It concludes that while this form of assessment poses a number of challenges, it can create valuable opportunities for the development of transferable twenty-first-century graduate employability skills as well as deep,
effective learning experiences, particularly – though not exclusively – in distance learning settings
The impact of workplace ergonomics and neck-specific exercise versus ergonomics and health promotion interventions on office worker productivity: A cluster-randomized trial
Objectives: Using an employer’s perspective, this study aimed to compare the immediate and longer-term impact of workplace ergonomics and neck-specific exercise versus ergonomics and health promotion information on health-related productivity among a general population of office workers and those with neck pain. Methods: A prospective one-year cluster randomized trial was conducted. Participants received an individualized workstation ergonomics intervention, combined with 12 weeks of either workplace neck-specific exercises or health promotion information. Health-related productivity at baseline, post-intervention and 12-months was measured with the Health and Work Performance Questionnaire. Intention-to-treat analysis was performed using multilevel mixed models. Results: We recruited 763 office workers from 14 organizations and allocated them to 100 clusters. For the general population of office workers, monetized productivity loss at 12 months [AU1563 (SD=1039); P=0.023]; and presenteeism at 12 months [2.0 (SD 1.2) versus 2.4 (SD 1.4); P=0.007] was lower in the exercise group compared to those in the health promotion information group. For office workers with neck pain, exercise participants had lower sickness absenteeism at 12 months compared to health promotion information participants [0.7 days (SD 1.0) versus 1.4 days (SD 3.1); P=0.012], despite a short-term increase in sickness absenteeism post-intervention compared to baseline for the exercise group [1.2 days (SD 2.2) versus 0.6 days (SD 0.9); P<0.001]. Conclusion: A workplace intervention combining ergonomics and neck-specific exercise offers possible benefits for sickness presenteeism and health-related productivity loss among a general population of office workers and sickness absenteeism for office workers with neck pain in the longer-term
Protecting the Kidney in Liver Transplant Recipients: Practice‐Based Recommendations From the American Society of Transplantation Liver and Intestine Community of Practice
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134132/1/ajt13765_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134132/2/ajt13765.pd
The generalised NMSSM at one loop: fine tuning and phenomenology
We determine the degree of fine tuning needed in a generalised version of the
NMSSM that follows from an underlying Z4 or Z8 R symmetry. We find that it is
significantly less than is found in the MSSM or NMSSM and extends the range of
Higgs mass that have acceptable fine tuning up to Higgs masses of mh ~ 130 GeV.
For universal boundary conditions analogous to the CMSSM the phenomenology is
rather MSSM like with the singlet states typically rather heavy. For more
general boundary conditions the singlet states can be light, leading to
interesting signatures at the LHC and direct detection experiments.Comment: 20 pages, 9 figures, matches published versio
Simulating growth, development, and yield of tillering pearl millet I. Leaf area profiles on main shoots and tillers
Pearl millet (Pennisteum americanum L.) is an essential crop in farming systems of the dry areas of the semi-arid tropics and its tillering habit is an important adaptive feature. This is the first paper in a series aiming at developing and validating a pearl millet simulation model that recognises tillers as functional entities, analogous to intercrops. The objective of this paper is to quantify the effects of total leaf number per axis (TLN), cultivar, plant density and axis number on parameters that are used to simulate potential leaf area per plant. Four cultivars with different phenology and tillering habit were grown under well-watered and well-fertilised conditions at two locations in India, covering a range of daylengths and plant densities. For selected plants, the area of fully expanded leaves was measured non-destructively. A bell-shaped function adequately described the relationship between individual leaf area and leaf position on an axis. Its shape was determined by the position (X0) and area (Y0) of the largest leaf and by the breadth and skewness of the leaf area profile curve. TLN affected all four parameters, although the association with Y0 was weak. Cultivar only affected Y0, suggesting that parameterising new cultivars is straightforward. The observed density effect confirmed that competition for light between axes started during stem elongation. The results highlighted the consistent differences between leaf area profiles of main shoots and tillers. For a high-tillering crop like pearl millet, modelling leaf area dynamics through individual leaves is justified, as this approach can potentially deal with cultivar and environmental effects on tillering
Passive sorting of asteroid material using solar radiation pressure
Understanding dust dynamics in asteroid environments is key for future science missions to asteroids and, in the long-term, also for asteroid exploitation. This paper proposes a novel way of manipulating asteroid material by means of solar radiation pressure (SRP). We envisage a method for passively sorting material as a function of its grain size where SRP is used as a passive in-situ ‘mass spec-trometer’. The analysis shows that this novel method allows an effective sorting of regolith material. This has immediate applications for sample return, and in-situ resource utilisation to separate different regolith particle sizes
The changing pattern of domestic cannabis cultivation in the UK and its impact on the cannabis market
With improvements in both technology and information cannabis is being increasingly grown indoors for domestic use, rather than being imported. This study examines 50 cannabis farms detected by an English police force, and examines the characteristics of the 61 suspects associated with them. The study highlights a UK pattern in domestic cultivation, that is moving away from large scale commercial cultivation, at times co-ordinated by South East Asian organised crime groups, to increased cultivation within residential premises by British citizens. Offenders range from those who have no prior criminal history to those who are serious and persistent offenders. The ramifications for law enforcement agencies and policy formers are discussed
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