3,666 research outputs found

    There is no simulation of n-qubit operations by a single Hamiltonian with 2-spin interaction

    Full text link
    Today's devices for quantum computing are still far from implementing useful and powerful quantum algorithms. Decoherence and the wish to resist the effects of errors in a system of quantum bits incurs a lot of overhead in the number of gates and qubits. From a theoretical perspective, controlled quantum simulation raises the hope to simulate the unitary quantum operationes generated by a Hamiltonian with 3-body interaction with a suitably designed element that is constructed of only 2-body interactions. That replacement would happen without any additional gates, and its possibility would be due to the ambiguity of the unit element of the Lie group connected with the algebra of traceless hermitian matrices. We show that this hope is void, and give a general proof for this for any order of interaction.Comment: 4 pages, ReVTeX4, twocolum

    The Fraunhofer Quantum Computing Portal - www.qc.fraunhofer.de - A web-based Simulator of Quantum Computing Processes

    Full text link
    Fraunhofer FIRST develops a computing service and collaborative workspace providing a convenient tool for simulation and investigation of quantum algorithms. To broaden the twenty qubit limit of workstation-based simulations to the next qubit decade we provide a dedicated high memorized Linux cluster with fast Myrinet interconnection network together with a adapted parallel simulator engine. This simulation service supplemented by a collaborative workspace is usable everywhere via web interface and integrates both hardware and software as collaboration and investigation platform for the quantum community. The beta test version realizes all common one, two and three qubit gates, arbitrary one and two bit gates, orthogonal measurements as well as special gates like Oracle, Modulo function, Quantum Fourier Transformation and arbitrary Spin-Hamiltonians up to 31 qubits. For a restricted gate set it feasible to investigate circuits with up to sixty qubits. URL: http://www.qc.fraunhofer.d

    Anchored heat kernel upper bounds on graphs with unbounded geometry and anti-trees

    Full text link
    We derive Gaussian heat kernel bounds on graphs with respect to a fixed origin for large times under the assumption of a Sobolev inequality and volume doubling on large balls. The upper bound from our previous work [KR22] is affected by a new correction term measuring the distance to the origin. The main result is then applied to anti-trees with unbounded vertex degree, yielding Gaussian upper bounds for this class of graphs for the first time. In order to prove this, we show that isoperimetric estimates with respect to intrinsic metrics yield Sobolev inequalities. Finally, we prove that anti-trees are Ahlfors regular and that they satisfy an isoperimetric inequality of a larger dimension.Comment: Comments welcome! 20 pages, 1 figur

    a web application to estimate scores from different patient-reported outcome measures on a common scale

    Get PDF
    Background Recently, a growing number of Item-Response Theory (IRT) models has been published, which allow estimation of a common latent variable from data derived by different Patient Reported Outcomes (PROs). When using data from different PROs, direct estimation of the latent variable has some advantages over the use of sum score conversion tables. It requires substantial proficiency in the field of psychometrics to fit such models using contemporary IRT software. We developed a web application (http://www.common- metrics.org), which allows estimation of latent variable scores more easily using IRT models calibrating different measures on instrument independent scales. Results Currently, the application allows estimation using six different IRT models for Depression, Anxiety, and Physical Function. Based on published item parameters, users of the application can directly estimate latent trait estimates using expected a posteriori (EAP) for sum scores as well as for specific response patterns, Bayes modal (MAP), Weighted likelihood estimation (WLE) and Maximum likelihood (ML) methods and under three different prior distributions. The obtained estimates can be downloaded and analyzed using standard statistical software. Conclusions This application enhances the usability of IRT modeling for researchers by allowing comparison of the latent trait estimates over different PROs, such as the Patient Health Questionnaire Depression (PHQ-9) and Anxiety (GAD-7) scales, the Center of Epidemiologic Studies Depression Scale (CES-D), the Beck Depression Inventory (BDI), PROMIS Anxiety and Depression Short Forms and others. Advantages of this approach include comparability of data derived with different measures and tolerance against missing values. The validity of the underlying models needs to be investigated in the future

    Changing faces : factors influencing the roles of researchers in real-world laboratories

    Get PDF
    Real-world laboratories (RwLs) often put researchers in highly demanding research contexts regarding their roles and self-conceptions. Helpful roles of researchers have been described but still little is known about the factors influencing the adoption of certain roles. Using data from three parallel RwLs in Wuppertal, Germany, we found four roles of researchers: the reflective scientist, the facilitator, the change agent and the (self-)reflexive scientist. We sequenced the RwLs into situations and analysed them by RwL process steps and conditions, considering the roles of researchers as outcomes. Although the conditions convey only limited explanatory power, there was a consistent picture that being pressured to carry out real-world action, having a practice partner with fewer resources and working without a functional project group is (in conjunction) sufficient to cause the researcher to partake in activities beyond conventional research. Process steps played a minor role. Our research on factors influencing the adoption of roles may help RwL researchers to perform their roles as intended

    BUSINESS MODELS FOR EGOVERNMENT THE BMeG METHOD

    Get PDF
    So far, business models have been investigated in the context of eCommerce focusing on economic issues but they do not consider the viewpoints of authorities embarking on public private partnerships for citizen services. This paper describes our modelling method BMeG that is dedicated to the planning of business models for eGovernment services. BMeG allows one to model options of value chains with various perspectives including advantages and disadvantages with impacts on policies. BMeG depicts the added value of potential partnerships and thus supports authorities to decide on alliances for public private partnerships or other financing models for eGovernment services

    www.common-metrics.org: a web application to estimate scores from different patient-reported outcome measures on a common scale

    Get PDF
    BACKGROUND: Recently, a growing number of Item-Response Theory (IRT) models has been published, which allow estimation of a common latent variable from data derived by different Patient Reported Outcomes (PROs). When using data from different PROs, direct estimation of the latent variable has some advantages over the use of sum score conversion tables. It requires substantial proficiency in the field of psychometrics to fit such models using contemporary IRT software. We developed a web application ( http://www.common-metrics.org ), which allows estimation of latent variable scores more easily using IRT models calibrating different measures on instrument independent scales. RESULTS: Currently, the application allows estimation using six different IRT models for Depression, Anxiety, and Physical Function. Based on published item parameters, users of the application can directly estimate latent trait estimates using expected a posteriori (EAP) for sum scores as well as for specific response patterns, Bayes modal (MAP), Weighted likelihood estimation (WLE) and Maximum likelihood (ML) methods and under three different prior distributions. The obtained estimates can be downloaded and analyzed using standard statistical software. CONCLUSIONS: This application enhances the usability of IRT modeling for researchers by allowing comparison of the latent trait estimates over different PROs, such as the Patient Health Questionnaire Depression (PHQ-9) and Anxiety (GAD-7) scales, the Center of Epidemiologic Studies Depression Scale (CES-D), the Beck Depression Inventory (BDI), PROMIS Anxiety and Depression Short Forms and others. Advantages of this approach include comparability of data derived with different measures and tolerance against missing values. The validity of the underlying models needs to be investigated in the future

    Минералого-петрохимические и геохимические черты околорудного метасоматизма в Западном золоторудном месторождении (Северное Забайкалье)

    Get PDF
    Приведены данные об условиях залегания, морфологии рудных тел, минеральном составе, физико-химических и термодинамических режимах образования руд Западного золоторудного месторождения Северного Забайкалья. Впервые показаны порядок минеральной зональности (структура) и минералого-петрохимические черты аподолеритовых околожильных метасоматических ореолов. Доказывается принадлежность последних к березитовой метасоматической формации, а месторождения - к золотой субформации золото-уран-полиметаллической березитовой рудной формации. Слабо контрастные аномалии золота, серебра, ртути приурочены к тыловым зонам околожильных метасоматических ореолов в непосредственном обрамлении слабозолотоносных (первые г/т) интервалов кварцевых жил. Аргументируются генетические связи околожильных метасоматических и геохимических ореолов с рудами и образование их в рудообразующем процессе позднепалеозойской металлогенической эпохи. Основные минералого-петрохимические и геохимические черты околожильного метасоматизма рассмотрены в сравнении с таковыми других месторождений Северо-Забайкальского золоторудного района

    The Frustration with Utilization: Why Have Improvements in Internal Phosphorus Utilization Efficiency in Crops Remained so Elusive?

    Get PDF
    Despite the attention internal phosphorus utilization efficiency (PUE) of crops has received in the literature, little progress in breeding crop cultivars with high PUE has been made. Surprisingly few studies have specifically investigated PUE; instead, genotypic variation for PUE has been investigated in studies that concurrently assess phosphorus acquisition efficiency (PAE). We hypothesized that genotypic differences in PAE confound PUE rankings because genotypes with higher PAE suffer a lower degree of P stress, resulting in lower PUE. The hypothesis was tested by comparing soil-based screening to a modified technique whereby rice genotypes were grown in individual containers with a single dose of solution P, to eliminate differences in P uptake among genotypes. Genotypic differences in PUE were apparent in root and shoot tissue using the modified nutrient solution technique, but PUE rankings showed no correlation with those from traditional soil-based screening. We conclude that PUE in soil-based screening systems is unavoidably linked with genotypic PAE, resulting in PUE rankings confounded by differences in P uptake. Only screening techniques assuring equal P uptake are suitable for the exploitation of genotypic variation for PUE
    corecore