Search results for "Dissipative system"
showing 10 items of 195 documents
Target states and control of molecular alignment in a dissipative medium
2006
Received 17 August 2006; published 14 November 2006We investigate how and to what extent molecular alignment can be controlled in a dissipative medium by asuitable train of laser pulses. We focus primarily on the extension of a scheme of control originally constructedfor unitary evolution. The procedure is applied to control the alignment of CO molecules in an Ar gas. Theparameters of the train of kicks—i.e., the intensity of each kick and the delay between them—are eitherobtained by a systematic procedure maximum strategy or by optimization by evolutionary algorithms.DOI: 10.1103/PhysRevA.74.053411 PACS number s : 32.80.Lg, 33.80. b, 42.50.Hz
Geometric versus numerical optimal control of a dissipative spin-12particle
2010
We analyze the saturation of a nuclear magnetic resonance (NMR) signal using optimal magnetic fields. We consider both the problems of minimizing the duration of the control and its energy for a fixed duration. We solve the optimal control problems by using geometric methods and a purely numerical approach, the grape algorithm, the two methods being based on the application of the Pontryagin maximum principle. A very good agreement is obtained between the two results. The optimal solutions for the energy-minimization problem are finally implemented experimentally with available NMR techniques.
Stability and Chaos
2010
In this chapter we study a larger class of dynamical systems that include but go beyond Hamiltonian systems. We are interested, on the one hand, in dissipative systems, i.e. systems that lose energy through frictional forces or into which energy is fed from exterior sources, and, on the other hand, in discrete, or discretized, systems such as those generated by studying flows by means of the Poincare mapping. The occurence of dissipation implies that the system is coupled to other, external systems, in a controllable manner. The strength of such couplings appears in the set of solutions, usually in the form of parameters. If these parameters are varied it may happen that the flow undergoes …
Pattern formation through phase bistability in oscillatory systems with space-modulated forcing.
2010
We propose a novel forcing technique of spatially extended self-oscillatory systems able to excite phase bistability and the dissipative structures associated with it. The forcing is time periodic at a frequency close to the oscillators' frequency and is spatially modulated. The effects of this type of forcing are demonstrated analytically and numerically in a directly driven complex Ginzburg-Landau equation. Both spatially periodic and spatially random drives prove to be effective.
Effect of the electromagnetic environment on arrays of small normal metal tunnel junctions: Numerical and experimental investigation
2000
We present results of a set of experiments to investigate the effect of dissipative external electromagnetic environment on tunneling in linear arrays of junctions in the weak tunneling regime. The influence of this resistance decreases as the number of junctions in the chain increases and ultimately becomes negligible. Further, there is a value of external impedance, typically \~5 k$\Omega$, at which the half-width of the zero-voltage dip in the conductance curve shows a maximum. Some new analytical formulae, based on the phase-correlation theory, along with numerical results will be presented.
Dissipative polarization domain walls as persisting topological defects
2018
We experimentally demonstrate the existence of dissipative polarization domain walls in a normally dispersive Kerr resonator. We excite and trap them with appropriate external signals thus realizing an all-optical buffer for topological data.
Coherent and incoherent electron transport along a disordered chain
1992
Abstract The Landauer-Buttiker approach is used to describe electron transport along a chain of scatterers which allow elastic as well as inelastic processes. The inelastic scattering takes place via side branches, coupling the chain to electron reservoirs which serve as a heat bath. In this approach, coherent and dissipative transport can be treated in a unified manner, and the suppression of quantum coherence effects for increasing coupling to the heat bath can be described. The influence of disorder on the transmission properties can be characterized by an appropriate coherence length in addition to the decay of the coherence due to dissipation.
Numerical simulation of free dissipative open quantum system and establishment of a formula for π
2020
We transform the system/reservoir coupling model into a one-dimensional semi-infinite discrete chain with nearest neighbor interaction through a unitary transformation, and, simulate the dynamics of free dissipative open quantum system. We investigate the consequences of such modeling, which is observed as finite size effect causing the recurrence of particle from the end of the chain. Afterwards, we determine a formula for π in terms of the matrix operational form, which indicates a robustness of the connection between quantum physics and basic mathematics. peerReviewed
Quantumness and memory of one qubit in a dissipative cavity under classical control
2019
Hybrid quantum-classical systems constitute a promising architecture for useful control strategies of quantum systems by means of a classical device. Here we provide a comprehensive study of the dynamics of various manifestations of quantumness with memory effects, identified by non-Markovianity, for a qubit controlled by a classical field and embedded in a leaky cavity. We consider both Leggett-Garg inequality and quantum witness as experimentally-friendly indicators of quantumness, also studying the geometric phase of the evolved (noisy) quantum state. We show that, under resonant qubit-classical field interaction, a stronger coupling to the classical control leads to enhancement of quant…
dc transport in dissipative disordered one-dimensional systems
1995
We present a numerical study of the dc transport properties of dissipative disordered chains which are described by linear ensembles of interconnected scatterers. The elastic-scattering amplitudes are derived from an Anderson Hamiltonian with diagonal (site) disorder. Inelastic scattering is accounted for by connecting the sites of the Anderson chain to separate external electron reservoirs. The calculated wave-vector-dependent transmission probabilities are discussed for chains with different lengths and for different degrees of dissipation. Using the Landauer-B\"uttiker approach we obtain the dc resistance of the considered samples. Our results demonstrate the rather intricate competition…