Commutator Relations Reveal Solvable Structures in Unambiguous State Discrimination

We present a criterion, based on three commutator relations, that allows to decide whether two self-adjoint matrices with non-overlapping support are simultaneously unitarily similar to quasidiagonal matrices, i.e., whether they can be simultaneously brought into a diagonal structure with 2x2-dimensional blocks. Application of this criterion to unambiguous state discrimination provides a systematic test whether the given problem is reducible to a solvable structure. As an example, we discuss unambiguous state comparison.Comment: 5 pages, discussion of related work adde

Isospin dependence of 6He+p optical potential and the symmetry energy

A consistent folding analysis of the elastic p(6He,6He)p scattering and charge exchange p(6He,6Li*)n reaction data measured at Elab=41.6A MeV has been performed within the coupled channels formalism. We have used the isovector coupling to link the isospin dependence of 6He+p optical potential to the cross section of p(6He,6Li*)n reaction exciting the 0+ isobaric analog state (IAS) at 3.563 MeV in 6Li. Based on these results and the Hartree-Fock calculation of asymmetric nuclear matter using the same isospin-dependent effective nucleon-nucleon interaction, we were able to confirm that the most realistic value of the symmetry energy Esym is around 31 MeV. Our analysis has also shown that the measured charge exchange p(6He,6Li*)n data are quite sensitive to the halo tail of the 6He density used in the folding calculation and the IAS of 6Li is likely to have a halo structure similar to that established for the ground state of 6He.Comment: Accepted for publication in Phys. Rev.

Mass transfer characteristics in structured packing for CO2 emission reduction processes

Acid gas treating and CO2 capture from flue gas by absorption have gained wide importance over the past few decades. With the implementation of more stringent environmental regulations and the awareness of the greenhouse effect, the need for efficient removal of acid gases such as CO2 (carbon dioxide) has increased significantly. Therefore, additional effort for research in this field is inevitable. For flue gas processes the ratio of absorption solvent to gas throughput is very different compared to acid gas treating processes owing to the atmospheric pressures and the dilution effect of combustion air. Moreover, in flue gas applications pressure drop is a very important process parameter. Packing types are required that allow for low pressure drop in combination with high interfacial areas at low liquid loading per square meter. The determination of interfacial areas in gas-liquid contactors by means of the chemical method (Danckwerts, P. V. Gas-liquid reactions; McGraw-Hill: London, 1970) has been very frequently applied. Unfortunately, many of the model systems proposed in the literature are reversible and therefore this condition possibly is not met. Versteeg et al. (Versteeg, G. F.; Kuipers, J. A. M.; Beckum, F. P. H.; van Swaaij, W. P. M. Chem. Eng. Sci. 1989, 44, 2292) have demonstrated that for reversible reactions the conditions for the determination of the interfacial area by means of the chemical method are much more severe. In a study by Raynal et al. (Raynal, L.; Ballaguet, J. P.; Berrere-Tricca, C. Chem. Eng. Sci. 2004, 59, 5395), it has been shown that there is a dependency of the interfacial area on the packing height. Unfortunately, most model systems used, e.g., CO2-caustic soda (as used by Raynal et al.), are much more complex and consist of (a set of) reversible reaction(s). The natures of these systems make the conditions at which the interfacial area can be determined much more severe and put more limitations on the process conditions and experimental equipment than a priori can be expected. Therefore, an extended absorption model is required to determine the conditions at which the interfacial area can be measured without detailed knowledge of the values of the liquid-side mass transfer coefficient, k1, beforehand.

Optimal Unambiguous State Discrimination of two density matrices and its link with the Fidelity

Recently the problem of Unambiguous State Discrimination (USD) of mixed quantum states has attracted much attention. So far, bounds on the optimum success probability have been derived [1]. For two mixed states they are given in terms of the fidelity. Here we give tighter bounds as well as necessary and sufficient conditions for two mixed states to reach these bounds. Moreover we construct the corresponding optimal measurement strategies. With this result, we provide analytical solutions for unambiguous discrimination of a class of generic mixed states. This goes beyond known results which are all reducible to some pure state case. Additionally, we show that examples exist where the bounds cannot be reached.Comment: 10 page

Mutually unbiased bases for the rotor degree of freedom

We consider the existence of a continuous set of mutually unbiased bases for the continuous and periodic degree of freedom that describes motion on a circle (rotor degree of freedom). By a singular mapping of the circle to the line, we find a first, but somewhat unsatisfactory, continuous set which does not relate to an underlying Heisenberg pair of complementary observables. Then, by a nonsingular mapping of the discrete angular momentum basis of the rotor onto the Fock basis for linear motion, we construct such a Heisenberg pair for the rotor and use it to obtain a second, fully satisfactory, set of mutually unbiased bases.Comment: 9 pages, 4 figure

Mutually unbiased bases in dimension six: The four most distant bases

We consider the average distance between four bases in dimension six. The distance between two orthonormal bases vanishes when the bases are the same, and the distance reaches its maximal value of unity when the bases are unbiased. We perform a numerical search for the maximum average distance and find it to be strictly smaller than unity. This is strong evidence that no four mutually unbiased bases exist in dimension six. We also provide a two-parameter family of three bases which, together with the canonical basis, reach the numerically-found maximum of the average distance, and we conduct a detailed study of the structure of the extremal set of bases.Comment: 10 pages, 2 figures, 1 tabl

Clavier DUCK : Utilisation d'un système de déduction de mots pour faciliter la saisie de texte sur écran tactile pour les non-voyants

International audienceTouch screens rapidly and significantly replace physical keyboards on mobile devices. Hence, text entry is now dependent on software (or virtual) keyboards that are widely used by sighted people, but raise accessibility issues for visually impaired users. These users rely on tactile exploration with vocal feedback of the whole screen for entering text, which is time consuming. We designed a software keyboard that aims reducing tactile exploration and speeding up text entry for VI users. It relies on the selection of the first letter of a word and rapid and inaccurate typing of the remaining letters. It then proposes a list of words having the same first letter and a similar total distance between letters. The evaluation with twelve VI users showed that this keyboard is very efficient for words larger than five characters. It also helps preventing certain typing errors.L'utilisation des écrans tactiles et en particulier les claviers logiciels est extrêmement compliquée pour les non-voyants qui manquent de repères physiques sur ce type d'appareil. Nous proposons dans cet article une solution clavier logicielle qui propose une liste de mots pouvant correspondre au mot recherché à partir de frappes approximatives des utilisateurs non-voyants. Cette technique évite ainsi à l'utilisateur d'explorer le clavier en permanence pour trouver précisément les caractères à saisir. Une première évaluation nous permet de montrer que notre système est efficace pour les mots de plus de quatre caractères. Il permet aussi d'éviter certains types d'erreur de frappe. Mots Clés Saisie de texte ; déficience visuelle ; écran tactile ; dispositifs mobiles ; clavier logiciel ; système déductif

Study of internal structures of 9,10Be and 10B in scattering of 4He from 9Be

A study of inelastic scattering and single-particle transfer reactions was performed by an alpha beam at 63 MeV on a 9$Be target. Angular distributions of the differential cross sections for the 9Be(4He,4He')9Be*, 9Be(4He,3He)10Be and 9Be(4He,t)10B reactions were measured. Experimental angular distributions of the differential cross sections for the ground state and a few low-lying states were analyzed in the framework of the optical model, coupled channels and distorted-wave Born approximation. An analysis of the obtained spectroscopic factors was performed.Comment: 16 pages, 7 figures, 3 tables, regular paper, mispritns are corrected in new versio