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1.
Chaotic systems perform well as a new rich source of
cryptography and pseudo-random coding. Unfortunately their digital
dynamical properties would degrade due to the finite computing
precision. Proposed in this paper is a modified digital chaotic
sequence generator based on chaotic logistic systems with a coupling
structure where one chaotic subsystem generates perturbation signals
to disturb the control parameter of the other one. The numerical
simulations show that the length of chaotic orbits, the output
distribution of chaotic system, and the security of chaotic
sequences have been greatly improved. Moreover the chaotic sequence
period can be extended at least by one order of magnitude longer
than that of the uncoupled logistic system and the difficulty in
decrypting increases 2128*2128 times indicating that the
dynamical degradation of digital chaos is effectively improved. A
field programmable gate array (FPGA) implementation of an algorithm
is given and the corresponding experiment shows that the output
speed of the generated chaotic sequences can reach 571.4~Mbps
indicating that the designed generator can be applied to the
real-time video image encryption. 相似文献
2.
We identify a border between regular and chaotic quantum dynamics. The border is characterized by a power-law decrease in the overlap between a state evolved under chaotic dynamics and the same state evolved under a slightly perturbed dynamics. For example, the overlap decay for the quantum kicked top is well fitted with [1+(q-1)(t/tau)2](1/(1-q)) (with the nonextensive entropic index q and tau depending on perturbation strength) in the region preceding the emergence of quantum interference effects. This region corresponds to the edge of chaos for the classical map from which the quantum chaotic dynamics is derived. 相似文献
3.
Jacquod P 《Physical review letters》2004,92(15):150403
Two particles, initially in a product state, become entangled when they come together and start to interact. Using semiclassical methods, we calculate the time evolution of the corresponding reduced density matrix rho(1), obtained by integrating out the degrees of freedom of one of the particles. We find that entanglement generation sensitively depends (i) on the interaction potential, especially on its strength and range, and (ii) on the nature of the underlying classical dynamics. Under general statistical assumptions, and for short-ranged interaction potentials, we find that P(t) decays exponentially fast in a chaotic environment, whereas it decays only algebraically in a regular system. In the chaotic case, the decay rate is given by the golden rule spreading of one-particle states due to the two-particle coupling, but cannot exceed the system's Lyapunov exponent. 相似文献
4.
We study the nonlinear dynamics of two-component Bose-Einstein condensates in one-dimensional periodic optical lattice
potentials. The stationary state perturbation solutions of the
coupled two-component nonlinear
Schrödinger/Gross-Pitaevskii equations are constructed by using the direct perturbation method. Theoretical analysis revels that the perturbation solution is the chaotic one, which
indicates the existence of chaos and chaotic region in parameter space. The corresponding numerical calculation results agree well with the analytical results. By applying the chaotic
perturbation solution, we demonstrate the atomic spatial population and the energy distribution of the system are chaotic generally. 相似文献
5.
We show that the onset of global chaos in a time periodically perturbed Hamiltonian system may occur at unusually small magnitudes of perturbation if the unperturbed system possesses more than one separatrix. The relevant scenario is the combination of the overlap in the phase space between resonances of the same order and their overlap in energy with chaotic layers associated with separatrices of the unperturbed system. We develop the asymptotic theory and verify it in simulations. 相似文献
6.
7.
We study the response of an ensemble of synchronized phase
oscillators to an external harmonic perturbation applied to one of
the oscillators. Our main goal is to relate the propagation of the
perturbation signal to the structure of the interaction network
underlying the ensemble. The overall response of the system is
resonant, exhibiting a maximum when the perturbation frequency
coincides with the natural frequency of the phase oscillators. The
individual response, on the other hand, can strongly depend on the
distance to the place where the perturbation is applied. For small
distances on a random network, the system behaves as a linear
dissipative medium: the perturbation propagates at constant speed,
while its amplitude decreases exponentially with the distance. For
larger distances, the response saturates to an almost constant
level. These different regimes can be analytically explained in
terms of the length distribution of the paths that propagate the
perturbation signal. We study the extension of these results to
other interaction patterns, and show that essentially the same
phenomena are observed in networks of chaotic oscillators. 相似文献
8.
We study the nonlinear dynamics of two-component Bose-Einstein condensates in one-dimensional periodic optical lattice potentials. The stationary state perturbation solutions of the coupled two-component nonlinear Schr(o)dinger/Gross-Pitaevskii equations are constructed by using the direct perturbation method. Theoretical analysis revels that the perturbation solution is the chaotic one, which indicates the existence of chaos and chaotic region in parameter space. The corresponding numerical calculation results agree well with the analytical results. By applying the chaotic perturbation solution, we demonstrate the atomic spatial population and the energy distribution of the system are chaotic generally. 相似文献
9.
10.
A. A. Zabolotskii 《Journal of Experimental and Theoretical Physics》2001,92(3):374-380
To analyze pulse dynamics in an optical system consisting of a periodic sequence of nonlinear media, a composite model is used. It includes a model of the resonance interaction of an ultrashort light pulse with the energy transition of the medium with allowance made for an upper level pump and an almost integrable model that describes the propagation of the light field in the other medium with a cubic nonlinearity and dispersion. Additional allowance is made for losses and other kinds of interaction by introducing perturbation terms. On the bases of the inverse scattering transform and perturbation theory, a simple method for analyzing specific features of soliton evolution in periodic systems of this kind is developed. It is used to describe various modes of soliton evolution in such a system, including chaotic dynamics. 相似文献
11.
For a Bose--Einstein condensate (BEC) confined in a double lattice
consisting of two weak laser standing waves we find the Melnikov
chaotic solution and chaotic region of parameter space by using the
direct perturbation method. In the chaotic region, spatial evolutions
of the chaotic solution and the corresponding distribution of
particle number density are bounded but unpredictable between their
superior and inferior limits. It is illustrated that when the
relation k1\approx k2 between the two laser wave vectors is
kept, the adjustment from k21 to k2\ge k1 can
transform the chaotic region into regular one or the other way round.
This suggests a feasible scheme for generating and controlling chaos,
which could lead to an experimental observation in the near future. 相似文献
12.
Stochastic time evolution in a nonseparable and nonintegrable quantum system is manifested by rapid dephasing of gaussian wavepackets, whose topological distribution in the coordinate-momentum space defines its irregular regions, while wavepackets initiated in regular regions exhibit quasiperiodic evolution. A gradual transition from quasiperiodic to chaotic dynamics with increasing energy is observed. 相似文献
13.
Fisher信息是估计理论中的重要概念,最近发现与量子信息中的纠缠判据具有密切联系.非旋波近似条件下,Dicke模型经典相空间表现为混沌动力学特征.本文详细考察了Dicke模型描述的光与物质相互作用系统中量子Fisher信息和自旋压缩动力学特性.结果表明:在短时瞬态情况下,无论初态处于规则区域还是混沌区域系统均表现为纠缠性质;但在长时稳态情况下,初态处于规则区域时系统纠缠消失,而初态处于混沌区域时系统则一直存在纠缠.通过与系统自旋压缩动力学性质相比较,发现量子Fisher信息可以更有效地刻画量子混沌.进一步考察初态处于规则和混沌区域时系统密度矩阵和纯度的动力学演化特性,发现混沌导致系统退相干现象发生,说明量子Fisher信息对混沌更敏感. 相似文献
14.
提出了一种带有预测函数的Hénon 混沌系统的广义预测控制快速算法.首先用时变遗忘因子的递推最小二乘方法辨识混沌系统,然后在广义预测控制的基础上引入了预测函数控制方法,并充分利用了预测信息的补偿作用.这种算法克服了广义预测控制中求解逆矩阵的缺点,提高了系统响应的速度,并且具有较强的跟踪给定信号、抑制系统参数摄动和随机噪声的能力.仿真结果验证了该方法的有效性.
关键词:
广义预测控制
预测函数
Hénon 混沌系统
参数辨识 相似文献
15.
P. V. Elyutin 《Journal of Experimental and Theoretical Physics》2006,102(1):182-187
The energy evolution of a quantum chaotic system under a perturbation that harmonically depends on time is studied in the
case of a large perturbation in which the transition rate calculated from the Fermi golden rule exceeds the frequency of the
perturbation. It is shown that the energy evolution retains its diffusive character, with a diffusion coefficient that is
asymptotically proportional to the magnitude of the perturbation and to the square root of the density of states. The results
are supported by numerical calculation. Energy absorption by the system and quantum-classical correlations are discussed.
The text was submitted by author in English. 相似文献
16.
Quantum Signatures of Chaos in Adiabatic Interaction Between a Trapped Ion and a Laser Standing Wave
LI Hui HAI Wen-Hua XU Jun 《理论物理通讯》2008,49(1):143-152
We study quantum motion around a classical heteroclinic point of a single trapped ion interacting with a strong laser standing wave. We construct a set of exact coherent states of the quantum system and from the exact solutions reveal that quantum signatures of chaos can be induced by the adiabatic interaction between the trapped ion and the laser standing wave, where the quantum expectation values of position and momentum correspond to the classically chaotic orbit. The chaotic region on the phase space is illustrated. The energy crossing and quantum resonance in time evolution and the exponentially increased Heisenberg uncertainty are found. The results suggest a theoretical scheme for controlling the unstable regular and chaotic motions. 相似文献
17.
In this Letter we deal with a nonlinear Schrödinger equation with chaotic, random, and nonperiodic cubic nonlinearity. Our goal is to study the soliton evolution, with the strength of the nonlinearity perturbed in the space and time coordinates and to check its robustness under these conditions. Here we show that the chaotic perturbation is more effective in destroying the soliton behavior, when compared with random or nonperiodic perturbation. For a real system, the perturbation can be related to, e.g., impurities in crystalline structures, or coupling to a thermal reservoir which, on the average, enhances the nonlinearity. We also discuss the relevance of such random perturbations to the dynamics of Bose-Einstein condensates and their collective excitations and transport. 相似文献
18.
19.
Non-linear dynamical behaviour of electron acoustic waves (EAWs) is studied in a magnetized non-thermal plasma (containing inertial cold electrons, inertialess hot electrons following non-thermal distribution function, and static ions) via a fluid dynamical approach. A linear dispersion relation is derived and the propagation of two possible modes and their evolution are studied through the different plasma configuration parameters, such as non-thermality and external magnetic field strength. In a non-linear perturbation regime, a reductive perturbation technique is employed to derive the non-linear evolution equation and the analysis is executed for travelling plane waves in terms of a non-linear dynamical system to enlighten the numerous aspects of the phase space dynamics. The results of numerical simulation predict the existence of a wide class of non-linear structures, namely solitonic, periodic, quasiperiodic, and chaotic depending upon different controlling plasma parameters. Also, Poincaré return map analysis confirms these non-linear structures of the EAWs. 相似文献
20.
We analyze the statistics of resonance widths in a many-body Fermi system with open decay channels. Depending on the strength of continuum coupling, such a system reveals growing deviations from the standard chi-square (Porter-Thomas) width distribution. The deviations emerge from the process of increasing interaction of intrinsic states through common decay channels; in the limit of perfect coupling this process leads to the superradiance phase transition. The width distribution depends also on the intrinsic dynamics (chaotic versus regular). The results presented here are important for understanding the recent experimental data concerning the width distribution for neutron resonances in nuclei. 相似文献