SPECIES I: Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars

The detection and subsequent characterisation of exoplanets are intimately linked to the characteristics of their host star. Therefore, it is necessary to study the star in detail in order to understand the formation history and characteristics of their companion(s). Our aims were to develop a community tool that allows the automated calculation of stellar parameters for a large number of stars, using high resolution echelle spectra and minimal photometric magnitudes, and introduce the first results in this work. We measured the equivalent widths of several iron lines and used them to solve the radiative transfer equation assuming local thermodynamic equilibrium to obtain the atmospheric parameters ($T_{\text{eff}}$, [Fe/H], logg and $\xi_t$). We used these values to derive the abundance of 11 chemical elements in the stellar photosphere (Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Ni, Cu and Zn). Rotation and macroturbulent velocity were obtained using temperature calibrators and synthetic line profiles to match the observed spectra of five absorption lines. Finally, by interpolating in a grid of MIST isochrones, we derived the mass, radius and age using a Bayesian approach. SPECIES obtains bulk parameters that are in good agreement with measured values from different existing catalogues, including when different methods are used to derive them. We find excellent agreement with previous works that used similar methodologies. We find discrepancies in the chemical abundances for some elements with respect to other works, which could be produced by differences in $T_{\text{eff}}$, or in the line list or the atomic line data used to derive them. We also obtained analytic relations to describe the correlations between different parameters, and we implemented new methods to better handle these correlations, which provides a better description of the uncertainties associated with the measurements.Comment: 28 pages, 26 figures, resubmitted to A&

Practical implementation of mutually unbiased bases using quantum circuits

The number of measurements necessary to perform the quantum state reconstruction of a system of qubits grows exponentially with the number of constituents, creating a major obstacle for the design of scalable tomographic schemes. We work out a simple and efficient method based on cyclic generation of mutually unbiased bases. The basic generator requires only Hadamard and controlled-phase gates, which are available in most practical realizations of these systems. We show how complete sets of mutually unbiased bases with different entanglement structures can be realized for three and four qubits. We also analyze the quantum circuits implementing the various entanglement classes.Comment: 5 pages, 2 color figures. Comments welcome

Unpolarized states and hidden polarization

We capitalize on a multipolar expansion of the polarisation density matrix, in which multipoles appear as successive moments of the Stokes variables. When all the multipoles up to a given order $K$ vanish, we can properly say that the state is $K$th-order unpolarized, as it lacks of polarization information to that order. First-order unpolarized states coincide with the corresponding classical ones, whereas unpolarized to any order tally with the quantum notion of fully invariant states. In between these two extreme cases, there is a rich variety of situations that are explored here. The existence of \textit{hidden} polarisation emerges in a natural way in this context.Comment: 7 pages, 3 eps-color figures. Submitted to PRA. Comments welcome

Velocity Statistics in the Two-Dimensional Granular Turbulence

We studied the macroscopic statistical properties on the freely evolving quasi-elastic hard disk (granular) system by performing a large-scale (up to a few million particles) event-driven molecular dynamics systematically and found that remarkably analogous to an enstrophy cascade process in the decaying two-dimensional fluid turbulence. There are four typical stages in the freely evolving inelastic hard disk system, which are homogeneous, shearing (vortex), clustering and final state. In the shearing stage, the self-organized macroscopic coherent vortices become dominant. In the clustering stage, the energy spectra are close to the expectation of Kraichnan-Batchelor theory and the squared two-particle separation strictly obeys Richardson law.Comment: 4 pages, 4 figures, to be published in PR

Nonlinear cross-Kerr quasiclassical dynamics

We study the quasiclassical dynamics of the cross-Kerr effect. In this approximation, the typical periodical revivals of the decorrelation between the two polarization modes disappear and they remain entangled. By mapping the dynamics onto the Poincare space, we find simple conditions for polarization squeezing. When dissipation is taken into account, the shape of the states in such a space is not considerably modified, but their size is reduced.Comment: 16 pages, 5 figure

Intrinsic Spectral Geometry of the Kerr-Newman Event Horizon

We uniquely and explicitly reconstruct the instantaneous intrinsic metric of the Kerr-Newman Event Horizon from the spectrum of its Laplacian. In the process we find that the angular momentum parameter, radius, area; and in the uncharged case, mass, can be written in terms of these eigenvalues. In the uncharged case this immediately leads to the unique and explicit determination of the Kerr metric in terms of the spectrum of the event horizon. Robinson's ``no hair" theorem now yields the corollary: One can ``hear the shape" of noncharged stationary axially symmetric black hole space-times by listening to the vibrational frequencies of its event horizon only.Comment: Final version with improved abstract, updated references, corrected typos, and additional discussio