Evolution of entanglement under an Ising-like Hamiltonian with particle losses

We present analytical compact solution for the density matrix and correlation functions of two collective-macroscopic spins evolving via Ising-like Hamiltonian in the presence of particle losses. The losses introduce non-local phase noise which destroys highly entangled states arising in the evolution. On the other hand, the states appearing at relatively short timescales, possessing EPR-like entanglement will survive. Applying our solutions to the recently proposed scheme to entangle two Bose-Einstein condensates, we estimate the optimal number of atoms for EPR correlations.Comment: 12 pages, 5 Figure

Convex set of quantum states with positive partial transpose analysed by hit and run algorithm

The convex set of quantum states of a composite $K \times K$ system with positive partial transpose is analysed. A version of the hit and run algorithm is used to generate a sequence of random points covering this set uniformly and an estimation for the convergence speed of the algorithm is derived. For $K\ge 3$ this algorithm works faster than sampling over the entire set of states and verifying whether the partial transpose is positive. The level density of the PPT states is shown to differ from the Marchenko-Pastur distribution, supported in [0,4] and corresponding asymptotically to the entire set of quantum states. Based on the shifted semi--circle law, describing asymptotic level density of partially transposed states, and on the level density for the Gaussian unitary ensemble with constraints for the spectrum we find an explicit form of the probability distribution supported in [0,3], which describes well the level density obtained numerically for PPT states.Comment: 11 pages, 4 figure

Quantum correlations protection through spin self-rephasing in 1-D Bose gas

System consisting of a number of trapped atoms evolving under the influence of external inhomogenous magnetic field undergoes spin dephasing: classically, since each atom feels different field along its trajectory, the spin rotation rates differ; as a result the average spin decays. In a quantum mechanical context this corresponds to entanglement of spin and spatial degrees of freedom and nontrivial internal spin dynamics. The spin dephasing can be prevented by tuning the interaction between the atoms. This phenomenon, called spin self-rephasing, has been observed experimentally and can increase the coherence time by a large factor. While such systems have been studied from a semiclassical point of view, a quantum mechanical description is limited, especially in the case of entangled states. In this work we provide a numerical simulation of an ab initio model and provide realistic examples of spin self-rephasing used to counteract the effect of inhomogenous magnetic field. We analyze in particular the joint effect of magnetic field inhomogeneity and interactions on the coherent and spin squeezed states evolution.Comment: 8 pages, 6 figure

The Genetic Basis of Graves' Disease

The presented comprehensive review of current knowledge about genetic factors predisposing to Graves’ disease (GD) put emphasis on functional significance of observed associations. In particular, we discuss recent efforts aimed at refining diseases associations found within the HLA complex and implicating HLA class I as well as HLA-DPB1 loci. We summarize data regarding non-HLA genes such as PTPN22, CTLA4, CD40, TSHR and TG which have been extensively studied in respect to their role in GD. We review recent findings implicating variants of FCRL3 (gene for FC receptor-like-3 protein), SCGB3A2 (gene for secretory uteroglobin-related protein 1- UGRP1) as well as other unverified possible candidate genes for GD selected through their documented association with type 1 diabetes mellitus: Tenr–IL2–IL21, CAPSL (encoding calcyphosine-like protein), IFIH1(gene for interferon-induced helicase C domain 1), AFF3, CD226 and PTPN2. We also review reports on association of skewed X chromosome inactivation and fetal microchimerism with GD. Finally we discuss issues of genotype-phenotype correlations in GD

A New Statistical Reconstruction Method for the Computed Tomography Using an X-Ray Tube with Flying Focal Spot

Abstract This paper presents a new image reconstruction method for spiral cone- beam tomography scanners in which an X-ray tube with a flying focal spot is used. The method is based on principles related to the statistical model-based iterative reconstruction (MBIR) methodology. The proposed approach is a continuous-to-continuous data model approach, and the forward model is formulated as a shift-invariant system. This allows for avoiding a nutating reconstruction-based approach, e.g. the advanced single slice rebinning methodology (ASSR) that is usually applied in computed tomography (CT) scanners with X-ray tubes with a flying focal spot. In turn, the proposed approach allows for significantly accelerating the reconstruction processing and, generally, for greatly simplifying the entire reconstruction procedure. Additionally, it improves the quality of the reconstructed images in comparison to the traditional algorithms, as confirmed by extensive simulations. It is worth noting that the main purpose of introducing statistical reconstruction methods to medical CT scanners is the reduction of the impact of measurement noise on the quality of tomography images and, consequently, the dose reduction of X-ray radiation absorbed by a patient. A series of computer simulations followed by doctor's assessments have been performed, which indicate how great a reduction of the absorbed dose can be achieved using the reconstruction approach presented here

Separability gap and large deviation entanglement criterion

For a given Hamiltonian $H$ on a multipartite quantum system, one is interested in finding the energy $E_0$ of its ground state. In the separability approximation, arising as a natural consequence of measurement in a separable basis, one looks for the minimal expectation value $\lambda_{\rm min}^{\otimes}$ of $H$ among all product states. For several concrete model Hamiltonians, we investigate the difference $\lambda_{\rm min}^{\otimes}-E_0$, called separability gap, which vanishes if the ground state has a product structure. In the generic case of a random Hermitian matrix of the Gaussian orthogonal ensemble, we find explicit bounds for the size of the gap which depend on the number of subsystems and hold with probability one. This implies an effective entanglement criterion applicable for any multipartite quantum system: If an expectation value of a typical observable among a given state is sufficiently distant from the average value, the state is almost surely entangled.Comment: 8 pages total, 3 figure

Electrical polarization switching in bulk single crystal GaFeO3_{3}

The electrical polarization switching on stoichiometric GaFeO$_{3}$ single crystal was measured, and a new model of atomic displacements responsible for the polarization reverse was proposed. The widely adapted mechanism of polarization switching in GaFeO$_{3}$ can be applied to stoichiometric, perfectly ordered crystals. However, the grown single crystals, as well as thin films of Ga-Fe-O, show pronounced atomic disorder. By piezoresponse force microscopy, the electrical polarization switching on a crystal surface perpendicular to the electrical polarization direction was demonstrated. Atomic disorder in the crystal was measured by X-ray diffraction and M\"ossbauer spectroscopy. These measurements were supported by ab initio calculations. By analysis of atomic disorder and electronic structure calculations, the energies of defects of cations in foreign cationic sites were estimated. The energies of the polarization switch were estimated, confirming the proposed mechanism of polarization switching in GaFeO$_{3}$ single crystals

Validation of QUALAS-T, a health-related quality of life instrument for teenagers with spina bifida

Introduction We aimed to develop and validate a self-reported QUAlity of Life Assessment in Spina bifida for Teenagers (QUALAS-T). Material and methods We drafted a 46-question pilot instrument using a patient-centered comprehensive item generation/refinement process. A group of 13–17 years olds with spina bifida (SB) was recruited online via social media and in person at SB clinics (2013–2015). Healthy controls were recruited during routine pediatrician visits. Final questions were identified based on clinical relevance, factor analysis and domain psychometrics. Teenagers with SB completed the validated generic Kidscreen-27 instrument. Results Median age of 159 participants was 15.2 years (42.0% male, 77.4% Caucasian), similar to 58 controls (p ≥ 0.06). There were 102 online and 57 clinic participants (82.8% of eligible). Patients, parents and an expert panel established face and content validity of the 2-domain, 10-question QUALAS-T. Internal consistency and test-retest reliability were high for the Family and Independence and Bladder and Bowel domains (Cronbach's alpha: 0.76–0.78, ICC: 0.72–0.75). The Bladder and Bowel domain is the same for QUALAS-T , QUALAS-A for adults and QUALAS-C for children. Correlations between QUALAS-T domains were low (r = 0.34), indicating QUALAS-T can differentiate between distinct HRQOL components. Correlations between QUALAS-T and Kidscreen-27 were also low (r ≤0.41). QUALAS-T scores were lower in teenagers with SB than without (p <0.0001). Conclusions QUALAS-T is a short, valid HRQOL tool for adolescents with SB, applicable in clinical and research settings. Since the Bladder & Bowel domains for all QUALAS versions are the same, Bladder and Bowel HRQOL can be measured on the same scale from age 8 through adulthood