Search results for " NOISE"

showing 10 items of 659 documents

CHANGES OF ELECTRONIC NOISE INDUCED BY OSCILLATING FIELDS IN BULK GaAs SEMICONDUCTORS

2008

A Monte Carlo study of hot-electron intrinsic noise in a n-type GaAs bulk driven by one or two mixed cyclostationary electric fields is presented. The noise properties are investigated by computing the spectral density of velocity fluctuations. An analysis of the noise features as a function of the amplitudes and frequencies of two applied fields is presented. Numerical results show that it is possible to reduce the intrinsic noise. The best conditions to realize this effect are discussed.

PhysicsElectronic noiseCyclostationary processGeneral MathematicsMonte Carlo methodQuantum noiseShot noiseField-mixing conditionGeneral Physics and AstronomySpectral densityNoise (electronics)Settore FIS/03 - Fisica Della MateriaComputational physicsElectric fieldFlicker noiseStatistical physicsMonte Carlo simulationFluctuation and Noise Letters
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Diffusion in Flashing Periodic Potentials

2005

The one-dimensional overdamped Brownian motion in a symmetric periodic potential modulated by external time-reversible noise is analyzed. The calculation of the effective diffusion coefficient is reduced to the mean first passage time problem. We derive general equations to calculate the effective diffusion coefficient of Brownian particles moving in arbitrary supersymmetric potential modulated: (i) by external white Gaussian noise and (ii) by Markovian dichotomous noise. For both cases the exact expressions for the effective diffusion coefficient are derived. We obtain acceleration of diffusion in comparison with the free diffusion case for fast fluctuating potentials with arbitrary profil…

PhysicsFluctuating Rectangular Periodic PotentialStatistical Mechanics (cond-mat.stat-mech)Mathematical analysisFOS: Physical sciencesSawtooth waveCondensed Matter - Soft Condensed MatterCondensed Matter PhysicsNoise (electronics)Electronic Optical and Magnetic Materialssymbols.namesakeAccelerationAdditive white Gaussian noisesymbolsSoft Condensed Matter (cond-mat.soft)Effective diffusion coefficientDiffusion (business)First-hitting-time modelBrownian motionCondensed Matter - Statistical Mechanics
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Noise-induced enhancement of stability in a metastable system with damping

2010

5 páginas, 5 figuras.-- PACS number(s): 05.40.-a, 02.50.-r

PhysicsFluctuation phenomena random processes noise and Brownian motionCondensed matter physicsProbability theory stochastic processes and statisticFunction (mathematics)Stability (probability)Settore FIS/03 - Fisica Della MateriaProbability theory stochastic processes and statistics; Fluctuation phenomena random processes noise and Brownian motionColors of noiseMetastabilityQuantum mechanicsParticleFirst-hitting-time modelNoise (radio)Brownian motion
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TRANSIENT DYNAMICS AND ASYMPTOTIC POPULATIONS IN A DRIVEN METASTABLE QUANTUM SYSTEM

2013

The transient dynamics of a periodically driven metastable quantum system, interacting with a heat bath, is investigated. The time evolution of the populations, within the framework of the Feynman–Vernon influ- ence functional and in the discrete variable representation, is analyzed by varying the parameters of the external driving. The results display strong non-monotonic behaviour of the populations with respect to the driving frequency.

PhysicsFluctuation phenomena random processes noise and Brownian motionDynamics (mechanics)quantum statistical methodGeneral Physics and AstronomyRELAXATIONDecoherenceSettore FIS/03 - Fisica Della MateriaNOISEQuantum systems with finite Hilbert spaceClassical mechanicsRELAXATION; NOISEMetastabilityQuantum systemTransient (oscillation)open system
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Noise effects in two different biological systems

2009

We investigate the role of the colored noise in two biological systems: (i) adults of Nezara viridula (L.) (Heteroptera: Pentatomidae), and (ii) polymer translocation. In the first system we analyze, by directionality tests, the response of N. viridula individuals to subthreshold signals plus noise in their mating behaviour. The percentage of insects that react to the subthreshold signal shows a nonmonotonic behaviour, characterized by the presence of a maximum, as a function of the noise intensity. This is the signature of the non-dynamical stochastic resonance phenomenon. By using a “soft” threshold model we find that the maximum of the input-output cross correlation occurs in the same ra…

PhysicsFluctuation phenomena random processes noise and Brownian motionQuantitative Biology::BiomoleculesCondensed matter physicsBistabilityStochastic resonanceStochastic processMolecular dynamics Brownian dynamicThermal fluctuationsMolecular interactionWhite noiseNoise in biological systemCondensed Matter PhysicsMolecular physicsSettore FIS/07 - Fisica Applicata(Beni Culturali Ambientali Biol.e Medicin)Electronic Optical and Magnetic MaterialsColors of noiseBrownian dynamicsPolymermembrane-protein interactionsNoise (radio)Biophysical mechanisms of interaction
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Dynamics of a FitzHugh-Nagumo system subjected to autocorrelated noise

2008

We analyze the dynamics of the FitzHugh-Nagumo (FHN) model in the presence of colored noise and a periodic signal. Two cases are considered: (i) the dynamics of the membrane potential is affected by the noise, (ii) the slow dynamics of the recovery variable is subject to noise. We investigate the role of the colored noise on the neuron dynamics by the mean response time (MRT) of the neuron. We find meaningful modifications of the resonant activation (RA) and noise enhanced stability (NES) phenomena due to the correlation time of the noise. For strongly correlated noise we observe suppression of NES effect and persistence of RA phenomenon, with an efficiency enhancement of the neuronal respo…

PhysicsFluctuation phenomena random processes noise and Brownian motionSettore FIS/02 - Fisica Teorica Modelli E Metodi MatematiciAutocorrelationDynamics (mechanics)Mean and predicted responseModels of single neurons and networks; Noise in the nervous system; Fluctuation phenomena random processes noise and Brownian motion; Nonlinear dynamics and chaosFOS: Physical sciencesNoise in the nervous systemModels of single neurons and networkCondensed Matter PhysicsFitzhugh nagumoNonlinear dynamics and chaosStability (probability)Electronic Optical and Magnetic MaterialsPeriodic functionNoiseColors of noiseBiological Physics (physics.bio-ph)Statistical physicsPhysics - Biological Physics
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Moment Equations for a Spatially Extended System of Two Competing Species

2005

The dynamics of a spatially extended system of two competing species in the presence of two noise sources is studied. A correlated dichotomous noise acts on the interaction parameter and a multiplicative white noise affects directly the dynamics of the two species. To describe the spatial distribution of the species we use a model based on Lotka-Volterra (LV) equations. By writing them in a mean field form, the corresponding moment equations for the species concentrations are obtained in Gaussian approximation. In this formalism the system dynamics is analyzed for different values of the multiplicative noise intensity. Finally by comparing these results with those obtained by direct simulat…

PhysicsFluctuation phenomena random processes noise and Brownian motionSettore FIS/02 - Fisica Teorica Modelli E Metodi MatematiciStatistical Mechanics (cond-mat.stat-mech)Multiplicative white noiseFOS: Physical sciencesFluctuation phenomena random processes noise and Brownian motion; Nonlinear dynamics and nonlinear dynamical systems; Population dynamics and ecological pattern formationCondensed Matter PhysicsSpatial distributionMultiplicative noiseElectronic Optical and Magnetic MaterialsSystem dynamicsMean field theorySpatial ecologyQuantitative Biology::Populations and EvolutionStatistical physicsNonlinear dynamics and nonlinear dynamical systemCondensed Matter - Statistical MechanicsMoment equationsCoupled map latticePopulation dynamics and ecological pattern formation
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A low phase noise microwave source for high‐performance CPT Rb atomic clock

2021

Abstract Phase noise of the frequency synthesizer is one of the main limitations to the short‐term stability of microwave atomic clocks. Here, a low‐noise, simple‐architecture microwave frequency synthesizer for a coherent population trapping (CPT) clock is demonstrated. The synthesizer is mainly composed of a 100 MHz oven‐controlled crystal oscillator (OCXO), a microwave comb generator, and a direct digital synthesizer (DDS). The absolute phase noises of 3.417 GHz signal are measured to be −55 dBc/Hz, −81 dBc/Hz, −111 dBc/Hz and −134 dBc/Hz, respectively, for 1 Hz, 10 Hz, 100 Hz and 1 kHz offset frequencies, which shows only 1 dB deterioration at the second harmonic of the modulation frequ…

PhysicsFrequency synthesizereducation.field_of_studybusiness.industry020208 electrical & electronic engineeringPopulationComb generatordBc02 engineering and technologyAtomic clockTK1-9971Direct digital synthesizerPhase noise0202 electrical engineering electronic engineering information engineeringOptoelectronicsElectrical engineering. Electronics. Nuclear engineeringElectrical and Electronic EngineeringbusinesseducationCrystal oscillatorElectronics Letters
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Implications of surface noise for the motional coherence of trapped ions

2016

Electric noise from metallic surfaces is a major obstacle towards quantum applications with trapped ions due to motional heating of the ions. Here, we discuss how the same noise source can also lead to pure dephasing of motional quantum states. The mechanism is particularly relevant at small ion-surface distances, thus imposing a new constraint on trap miniaturization. By means of a free induction decay experiment, we measure the dephasing time of the motion of a single ion trapped 50~$\mu$m above a Cu-Al surface. From the dephasing times we extract the integrated noise below the secular frequency of the ion. We find that none of the most commonly discussed surface noise models for ion trap…

PhysicsGeneral PhysicsQuantum PhysicsAtomic Physics (physics.atom-ph)DephasingQuantum noiseFOS: Physical sciences02 engineering and technology021001 nanoscience & nanotechnology01 natural sciencesMathematical SciencesIonPhysics - Atomic PhysicsFree induction decayQuantum state0103 physical sciencesPhysical SciencesChemical SciencesMiniaturizationAtomic physicsQuantum Physics (quant-ph)010306 general physics0210 nano-technologyQuantumCoherence (physics)
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Measurement of the Sensitivity Function in a Time-Domain Atomic Interferometer

2008

We present here an analysis of the sensitivity of a time-domain atomic interferometer to the phase noise of the lasers used to manipulate the atomic wave packets. The sensitivity function is calculated in the case of a three-pulse Mach-Zehnder interferometer, which is the configuration of the two inertial sensors we are building at the Laboratoire National de Metrologie et d'Essais-Systeme de References Temps-Espace. We successfully compare this calculation to experimental measurements. The sensitivity of the interferometer is limited by the phase noise of the lasers as well as by residual vibrations. We evaluate the performance that could be obtained with state-of-the-art quartz oscillator…

PhysicsInterferometric visibilitybusiness.industryWave packetPhase-locked loopInterferometryOpticsPhase noiseSensitivity (control systems)Time domainElectrical and Electronic EngineeringbusinessInstrumentationCrystal oscillatorIEEE Transactions on Instrumentation and Measurement
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