Optimal distillation of three-qubit W states

Some of the asymmetric three qubit $W$ states are used for perfect teleportation, superdense coding and quantum information splitting. We present the protocols for the optimal distillation of the asymmetric as well as the symmetric $W$ states from a single copy of any three qubit $W$ class pure state.Comment: 10 page

Grids of stellar models including second harmonic and colours: Solar composition

Grids of stellar evolution are required in many fields of astronomy/astrophysics, such as planet hosting stars, binaries, clusters, chemically peculiar stars, etc. In this study, a grid of stellar evolution models with updated ingredients and {recently determined solar abundaces} is presented. The solar values for the initial abundances of hydrogen, heavy elements and mixing-length parameter are 0.0172, 0.7024 and 1.98, respectively. The mass step is small enough (0.01 M$_\odot$) that interpolation for a given star mass is not required. The range of stellar mass is 0.74 to 10.00 M$_\odot$. We present results in different forms of tables for easy and general application. The second stellar harmonic, required for analysis of apsidal motion of eclipsing binaries, is also listed. We also construct rotating models to determine effect of rotation on stellar structure and derive fitting formula for luminosity, radius and the second stellar harmonic as a function of rotational parameter. We also compute and list colours and bolometric corrections of models required for transformation between theoretical and observational results. The results are tested for the Sun, the Hyades cluster, the slowly rotating chemically peculiar Am stars and the eclipsing binaries with apsidal motion. The theoretical and observational results along isochrones are in good agreement. The grids are also applicable to rotating stars provided that equatorial velocity is given.Comment: 13 Figures 21 pages. Accepted by RA

Modelling early-type stars in eclipsing binaries of open clusters: a new method for age determination from ratio of radii

Binary systems, in particular eclipsing binaries, are essential sources of our knowledge of the fundamental properties of stars. The ages of binaries, members of open clusters, are constrained by their own fundamental properties and by those of the hosting cluster. The ages of eleven open clusters are here found by constructing models for the components of twelve eclipsing binaries. The difference between the ages we found and the ages of the clusters derived from isochrone fitting is up to 40%. For the binary system V497 Cep in NGC 7160, the difference is about 100%. Binary systems whose primary component is aboutto complete main-sequence life time, such as V453 Cyg and V906 Sco, are the most suitable systems for age determination. Using model results for these stars, we derive an expression for sensitive and uncomplicated relative age determination of binary systems (age divided by the main-sequence life time of the primary star). The expression is given as logarithm of radii ratio divided by a logarithm of mass ratio. Two advantages of this expression are that (i) it is nearly independent of assumed chemical composition of the models because of the appearance of the ratio of radii, and (ii) the ratios of radii and masses are observationally much more precise than their absolute values. We also derive another expression using luminosities rather than radii and compare results.Comment: 12 pages, 6 figures, accepted by PAS