177,065 research outputs found
An algorithm to explore entanglement in small systems
No full textA quantum state’s entanglement across a bipartite cut can be quantified with entanglement entropy or, more generally, Schmidt norms. Using only Schmidt decompositions, we present a simple iterative algorithm to maximize Schmidt norms. Depending on the choice of norm, the optimizing states maximize or minimize entanglement, possibly across several bipartite cuts at the same time and possibly only among states in a specified subspace. Recognizing that convergence but not success is certain, we use the algorithm to explore topics ranging from fermionic reduced density matrices and varieties of pure quantum states to absolutely maximally entangled states and minimal output entropy of channels.</jats:p
Generalized Pauli constraints in large systems: the Pauli principle dominates
No full textLately, there has been a renewed interest in fermionic 1-body reduced density
matrices and their restrictions beyond the Pauli principle. These restrictions
are usually quantified using the polytope of allowed, ordered eigenvalues of
such matrices. Here, we prove this polytope's volume rapidly approaches the
volume predicted by the Pauli principle as the dimension of the 1-body space
grows, and that additional corrections, caused by generalized Pauli
constraints, are of much lower order unless the number of fermions is small.
Indeed, we argue the generalized constraints are most restrictive in
(effective) few-fermion settings with low Hilbert space dimension.Comment: Published version; 37 pages, 5 figure
A Flea on Schrodinger's Cat
No full textContains fulltext :
111305.pdf (Author’s version preprint ) (Open Access
Entropy and Entanglement Bounds for Reduced Density Matrices of Fermionic States
No full textUnlike bosons, fermions always have a non-trivial entanglement. Intuitively, Slater determinantal states should be the least entangled states. To make this intuition precise we investigate entropy and entanglement of fermionic states and prove some extremal and near extremal properties of reduced density matrices of Slater determinantal states
Calculation of the critical temperature of a dilute Bose gas in the Bogoliubov approximation
No full textFollowing an earlier calculation in 3D, we calculate the 2D critical temperature of a dilute, translation-invariant Bose gas using a variational formulation of the Bogoliubov approximation introduced by Critchley and Solomon in 1976. This provides the first analytical calculation of the Kosterlitz-Thouless transition temperature that includes the constant in the logarithm
Quantum spin systems versus Schrodinger operators: A case study in spontaneous symmetry breaking
No full textSpontaneous symmetry breaking (SSB) is mathematically tied to some limit, but must physically occur, approximately, before the limit. Approximate SSB has been independently understood for Schrodinger operators with double well potential in the classical limit [1, 2] and for quantum spin systems in the thermodynamic limit [3, 4]. We relate these to each other in the context of the Curie-Weiss model, establishing a remarkable relationship between this model (for finite N) and a discretized Schrodinger operator with double well potential
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Relationship between the time interval from antenatal corticosteroid administration until preterm birth and the occurrence of respiratory morbidity
No full textAbstract not availableFemke F. Wilms, Jolande Y. Vis, Desiree A.P.M. Pattinaja, Rosanna A. Kuin, Monique C. Stam, Janine M. Reuvers, Ben Willem J. Mo
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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