Theory of Spin Relaxation in Two-Electron Lateral Coupled Si/SiGe Quantum Dots

Highly accurate numerical results of phonon-induced two-electron spin relaxation in silicon double quantum dots are presented. The relaxation, enabled by spin-orbit coupling and the nuclei of $^{29}$Si (natural or purified abundance), are investigated for experimentally relevant parameters, the interdot coupling, the magnetic field magnitude and orientation, and the detuning. We calculate relaxation rates for zero and finite temperatures (100 mK), concluding that our findings for zero temperature remain qualitatively valid also for 100 mK. We confirm the same anisotropic switch of the axis of prolonged spin lifetime with varying detuning as recently predicted in GaAs. Conditions for possibly hyperfine-dominated relaxation are much more stringent in Si than in GaAs. For experimentally relevant regimes, the spin-orbit coupling, although weak, is the dominant contribution, yielding anisotropic relaxation rates of at least two order of magnitude lower than in GaAs.Comment: 11 pages, 10 figure

The Bravyi-Kitaev transformation for quantum computation of electronic structure

Quantum simulation is an important application of future quantum computers with applications in quantum chemistry, condensed matter, and beyond. Quantum simulation of fermionic systems presents a specific challenge. The Jordan-Wigner transformation allows for representation of a fermionic operator by O(n) qubit operations. Here we develop an alternative method of simulating fermions with qubits, first proposed by Bravyi and Kitaev [S. B. Bravyi, A.Yu. Kitaev, Annals of Physics 298, 210-226 (2002)], that reduces the simulation cost to O(log n) qubit operations for one fermionic operation. We apply this new Bravyi-Kitaev transformation to the task of simulating quantum chemical Hamiltonians, and give a detailed example for the simplest possible case of molecular hydrogen in a minimal basis. We show that the quantum circuit for simulating a single Trotter time-step of the Bravyi-Kitaev derived Hamiltonian for H2 requires fewer gate applications than the equivalent circuit derived from the Jordan-Wigner transformation. Since the scaling of the Bravyi-Kitaev method is asymptotically better than the Jordan-Wigner method, this result for molecular hydrogen in a minimal basis demonstrates the superior efficiency of the Bravyi-Kitaev method for all quantum computations of electronic structure

The Structure of the QCD Potential in 2+1 Dimensions

We calculate the screening and anti-screening contributions to the inter-quark potential in 2+1 dimensions, which is relevant to the high temperature limit of QCD. We demonstrate that the relative strength of screening to anti-screening agrees with the 3+1 dimensional theory to better than one percent accuracy.Comment: 9 pages, LaTeX, no figures, version to appear in Journa

Eccentric and Isometric Hip Adduction Strength in Male Soccer Players With and Without Adductor-Related Groin Pain An Assessor-Blinded Comparison:An Assessor-Blinded Comparison

BACKGROUND: Adductor-related pain is the most common clinical finding in soccer players with groin pain and can be a long-standing problem affecting physical function and performance. Hip adductor weakness has been suggested to be associated with this clinical entity, although it has never been investigated. PURPOSE: To investigate whether isometric and eccentric hip strength are decreased in soccer players with adductor-related groin pain compared with asymptomatic soccer controls. The hypothesis was that players with adductor-related groin pain would have lower isometric and eccentric hip adduction strength than players without adductor-related groin pain. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Male elite and subelite players from 40 teams were contacted. In total, 28 soccer players with adductor-related groin pain and 16 soccer players without adductor-related groin pain (asymptomatic controls) were included in the study. In primary analysis, the dominant legs of 21 soccer players with adductor-related groin pain (≥4 weeks duration) were compared with the dominant legs of 16 asymptomatic controls using a cross-sectional design. The mean age of the symptomatic players was 24.5 ± 2.5 years, and the mean age of the asymptomatic controls was 22.9 ± 2.4 years. Isometric hip strength (adduction, abduction, and flexion) and eccentric hip strength (adduction) were assessed with a handheld dynamometer using reliable test procedures and a blinded assessor. RESULTS: Eccentric hip adduction strength was lower in soccer players with adductor-related groin pain in the dominant leg (n = 21) compared with asymptomatic controls (n = 16), namely 2.47 ± 0.49 versus 3.12 ± 0.43 N·m/kg, respectively (P < .001). No other hip strength differences were observed between symptomatic players and asymptomatic controls for the dominant leg (P = .35-.84). CONCLUSION: Large eccentric hip adduction strength deficits were found in soccer players with adductor-related groin pain compared with asymptomatic soccer players, while no isometric strength differences were observed between the groups

Colour Charges and the Anti-Screening Contribution to the Interquark Potential

Asymptotic freedom arises from the dominance of anti-screening over screening in non-abelian gauge theories. In this paper we will present a simple and physically appealing derivation of the anti-screening contribution to the interquark potential. Our method allows us to identify the dominant gluonic distribution around static quarks. Extensions are discussed.Comment: 7 pages, LaTe

Geoacoustic Inversion of Ship Radiated Noise in Shallow Water Using Data From a Single Hydrophone

The Centre for Maritime Research and Experimentation conducted a geoacoustic inverse experiment in the Mediterranean Sea in the summer of 2012. Among the objectives was to employ an autono- mous underwater vehicle to collect acoustic data to invert for properties of the seafloor. Inversion results for the compression wave speed in the bottom and the source spectrum of the R/V Alliance during a close approach to the bottom moored vehicle are presented. The estimated wave speed was 1529 m/s (r ¼ 10). The source spectrum of the Alliance was estimated across more than six octaves of frequency

Comparative effectiveness and safety of edoxaban versus warfarin in patients with atrial fibrillation:A nationwide cohort study

Background and purposeThe effectiveness and safety of edoxaban 60 mg and 30 mg for stroke prevention compared with warfarin in patients with atrial fibrillation have not been well-described in a nationwide cohort of Caucasian patients treated in standard clinical practice.MethodsWe used Danish nationwide registries to identify patients with atrial fibrillation during June 2016 and November 2018 who were treated with edoxaban or warfarin and computed rates per 100 person-years of thromboembolic, all-cause mortality, and bleeding events using an inverse probability of treatment weighting approach to account for baseline confounding. We used weighted pooled logistic regression to compute hazard ratios with 95% confidence intervals comparing events between edoxaban 60 mg and warfarin users; edoxaban 30 mg was not included in formal comparisons.ResultsWe identified 6451 atrial fibrillation patients, mean age was 72 years and 40% were females. A total of 1772 patients were treated with edoxaban 60 mg, 537 with edoxaban 30 mg, and 4142 with warfarin. The median CHA2DS2-VASc score was similar between warfarin and edoxaban 60 mg with a score of 3 (interquartile range (IQR) 2-4). In the inverse probability of treatment-weighted pseudo-population, the thromboembolic event rate for edoxaban 60 mg was 0.95 and 1.0 for warfarin, corresponding weighted hazard ratio of 1.00 (95% confidence intervals (CI) 0.59, 1.71). Edoxaban 60 mg users were associated with lower rates of all-cause mortality (3.93) compared to warfarin (6.04), with a hazard ratio of 0.64 (95% CI 0.47 to 0.88). The event rates for bleeding were 3.36 and 3.14, respectively; hazard ratio 1.09 (95% CI 0.77, 1.57).ConclusionEdoxaban 60 mg is a safe and effective treatment compared with warfarin for stroke prevention in routine clinical care for Danish (mainly Caucasian) patients with AF, with non-significantly different risks for stroke and clinically relevant bleeding, but lower all-cause mortality