Simple Non-Markovian Microscopic Models for the Depolarizing Channel of a Single Qubit

The archetypal one-qubit noisy channels ---depolarizing, phase-damping and amplitude-damping channels--- describe both Markovian and non-Markovian evolution. Simple microscopic models for the depolarizing channel, both classical and quantum, are considered. Microscopic models which describe phase damping and amplitude damping channels are briefly reviewed.Comment: 13 pages, 2 figures. Title corrected. Paper rewritten. Added references. Some typos and errors corrected. Author adde

IMPACT OF IONOSPHERIC HORIZONTAL ASYMMETRY ON ELECTRON DENSITY PROFILES DERIVED BY GNSS RADIO OCCULTATION

The ‘Onion-peeling' algorithm is a very common technique used to invert Radio Occultation (RO) data in the ionosphere. Because of the implicit assumption of spherical symmetry for the electron density distribution in the ionosphere, the standard Onion-peeling algorithm could give erroneous concentration values in the retrieved electron density profile. In particular, this happens when strong horizontal ionospheric electron density gradients are present, like for example in the Equatorial Ionization Anomaly (EIA) region during high solar activity periods. In this work, using simulated RO TEC data computed by means of the NeQuick2 ionospheric electron density model and ideal RO geometries, we tried to formulate and evaluate an asymmetry level indicator for quasi-horizontal radio occultation observations. This asymmetry index is based on the electron density variation that a ray may experience along its propagation path (satellite to satellite link) in a RO event. Our previous qualitative assessment based on ideal simulations of RO events shows very high correlation between our asymmetry index and Onion-peeling retrieval errors (Shaikh M.M. et al 2013): errors produced by Onion-peeling in the retrieval of NmF2 and VTEC are larger at the geographical locations where our asymmetry index indicates high asymmetry in the ionosphere. In this contribution, an analysis of the asymmetry index has been carried out for the first time using real radio occultation geometries taken from COSMIC mission. This has been done for COSMIC events for which, considering the same RO geometry, simulated Limb-TEC (LTEC) under NeQuick2 background were quite close to the real LTEC observations (providing ‘quasi' co-located vertical profiles of electron density after inversion). On the basis of the outcomes of our work, for a given geometry of a real RO event and using a suitable ionospheric model, we will try to investigate the possibility to predict ionospheric asymmetry expected for the particular RO geometry considered. We could also try to evaluate, in advance, its impact on the inverted electron density profile, providing an indication of the expected product quality, if standard Onion-peelingalgorithm will be adopted to invert the observables. Results presented in this paper are initial outcomes based on our asymmetry evaluation algorith

On the Stability of Stochastic Parametrically Forced Equations with Rank One Forcing

We derive simplified formulas for analyzing the stability of stochastic parametrically forced linear systems. This extends the results in [T. Blass and L.A. Romero, SIAM J. Control Optim. 51(2):1099--1127, 2013] where, assuming the stochastic excitation is small, the stability of such systems was computed using a weighted sum of the extended power spectral density over the eigenvalues of the unperturbed operator. In this paper, we show how to convert this to a sum over the residues of the extended power spectral density. For systems where the parametric forcing term is a rank one matrix, this leads to an enormous simplification.Comment: 16 page

Synthesis by molten salt method of the AFeO3 system (A = La, Gd) and its structural, vibrational and internal hyperfine magnetic field characterization

Polycrystalline samples of LaFeO3 and GdFeO3 were synthesized by the molten salt method. Some properties and the quality of the resulting compounds were investigated. The crystal structure and purity of the samples was determined through X-ray diffraction and Rietveld analysis. The vibrational properties were characterized by Raman and IR spectroscopy. M\"ossbauer spectroscopy was used to determine the ionic state of the Fe ions and the internal hyperfine magnetic fields Considerable reduction of the heat treatment (temperature and time) for the reaction to take place was achieved without detriment of the quality of the compounds.Comment: 10 figure