Simulations of "Decoherence" with Noise Pulses

A simulation of decoherence as random noise in the Hamiltonian is studied. The full Hamiltonian for the rf Squid is used, with the parameters chosen such that there is a double-potential well configuration where the two quasi-degenerate lowest levels are well separated from the rest. The results for these first two levels are in quantitative agreement with expectations from the ``spin 1/2'' picture for the behavior of a two-state system.Comment: Four pages, three figures. Contribution to special issue of Molecular Physics in honor of R. A. Harri

Strategies for using GAPDs as tracker detectors in future linear colliders

AbstractThis work presents the development of a Geiger-mode Avalanche PhotoDiode pixel detector in standard CMOS technologies aimed at the vertex and tracker regions of future linear colliders, i.e. the International Linear Collider and the Compact LInear Collider. In spite of all the advantages that characterize this technology, GAPD detectors suffer from noise pulses that cannot be distinguished from real events and low fill-factors that reduce the detection efficiency. To comply with the specifications imposed by the next generation of particle colliders, solutions to minimize the intrinsic noise pulses and increase the fill-factor have been thoroughly investigated

Transient response measurements on a satellite system

A set of instruments designed to detect the occurance of electrical breakdown was flown on a synchronous-orbit satellite. The LeRC sensors were installed on cables inside the vehicle. Accordingly, they respond to signals coupled into the satellite wiring system. The SRI sensors were located on the exterior of the vehicle and detected the RF noise pulses associated with surface breakdowns. The results of the earlier SRI program are being used to design and develop a set of intrumentation suitable for inclusion as a general piggy-back package for the detection of the onset of satellite charging and breakdowns on synchronous orbit satellites

Optimal escape from metastable states driven by non-Gaussian noise

5 pages, 2 figures5 pages, 2 figures5 pages, 2 figuresWe investigate escape processes from metastable states that are driven by non-Gaussian noise. Using a path integral approach, we define a weak-noise scaling limit that identifies optimal escape paths as minima of a stochastic action, while retaining the infinite hierarchy of noise cumulants. This enables us to investigate the effect of different noise amplitude distributions. We find generically a reduced effective potential barrier but also fundamental differences, particularly for the limit when the non-Gaussian noise pulses are relatively slow. Here we identify a class of amplitude distributions that can induce a single-jump escape from the potential well. Our results highlight that higher-order noise cumulants crucially influence escape behaviour even in the weak-noise limit

Impaired Auditory Temporal Selectivity in the Inferior Colliculus of Aged Mongolian Gerbils

Aged humans show severe difficulties in temporal auditory processing tasks (e.g., speech recognition in noise, low-frequency sound localization, gap detection). A degradation of auditory function with age is also evident in experimental animals. To investigate age-related changes in temporal processing, we compared extracellular responses to temporally variable pulse trains and human speech in the inferior colliculus of young adult (3 month) and aged (3 years) Mongolian gerbils. We observed a significant decrease of selectivity to the pulse trains in neuronal responses from aged animals. This decrease in selectivity led, on the population level, to an increase in signal correlations and therefore a decrease in heterogeneity of temporal receptive fields and a decreased efficiency in encoding of speech signals. A decrease in selectivity to temporal modulations is consistent with a downregulation of the inhibitory transmitter system in aged animals. These alterations in temporal processing could underlie declines in the aging auditory system, which are unrelated to peripheral hearing loss. These declines cannot be compensated by traditional hearing aids (that rely on amplification of sound) but may rather require pharmacological treatment

Non-Gaussian, non-dynamical stochastic resonance

The archetypal system demonstrating stochastic resonance is nothing more than a threshold triggered device. It consists of a periodic modulated input and noise. Every time an output crosses the threshold the signal is recorded. Such a digitally filtered signal is sensitive to the noise intensity. There exist the optimal value of the noise intensity resulting in the "most" periodic output. Here, we explore properties of the non-dynamical stochastic resonance in non-equilibrium situations, i.e. when the Gaussian noise is replaced by an $\alpha$-stable noise. We demonstrate that non-equilibrium $\alpha$-stable noises, depending on noise parameters, can either weaken or enhance the non-dynamical stochastic resonance.Comment: 5 pages, 6 figurure