共查询到20条相似文献,搜索用时 31 毫秒
1.
In the tomography representation we propose a new approach, which describes the dynamics of quantum particles by the Kolmogorov equations for non-negative propagators. To solve the Kolmogorov equations we use a diffusive Markovian random processes described by the related nonlinear stochastic Langevin equations. As a result the dynamics of quantum particles is described by the proposed numerical scheme combining both Langevin dynamics and Monte Carlo methods. We test the developed approach by applying it to the wave packet dynamics in harmonic potentials and to particle tunneling through a barrier. 相似文献
2.
M. Machida T. Kano M. Okumura T. Imamura T. Koyama 《Journal of Physics and Chemistry of Solids》2008,69(12):3221-3224
We numerically study quantum effects in intrinsic Josephson junctions of layered high-Tc superconductors in order to explain recent experimental observations on the switching rate enhancement in the low temperature quantum regime. We pay attention to the capacitive coupling between neighboring junctions and perform simulations for the Schrödinger equation derived from the Hamiltonian describing the capacitive coupling. The simulation results reveal that the phase dynamics show synchronous behaviors when entering the quantum regime. This is qualitatively consistent with the experimental result. 相似文献
3.
We identify fundamental mechanisms of electron and hole dynamics in self-organized InAs/GaAs quantum dots (QDs) subject to vertical electric fields by photocurrent investigations. We propose a spin–flip mechanism involving a spin exchange between neighboring QDs. The spin–flip process is revealed in the photocurrent dynamics when the exciton population increases unexpectedly with reverse bias. 相似文献
4.
J. Gomis J. Martínez-Pastor B. Alén D. Granados J. M. García P. Roussignol 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(4):471-477
We present a study of the primary optical transitions
and recombination dynamics in InGaAs self-assembled quantum
nanostructures with different shape. Starting from the same
quantum dot seeding layer, and depending on the overgrowth
conditions, these new nanostructures can be tailored in shape and
are characterized by heights lower than 2 nm and base lengths
around 100 nm. The geometrical shape strongly influences the
electronic and optical properties of these nanostructuctures. We
measure for them ground state optical transitions in the range
1.25–1.35 eV and varying energy splitting between their excited
states. The temperature dependence of the exciton recombination
dynamics is reported focusing on the intermediate temperature
regime (before thermal escape begins to be important). In this
range, an important increase of the effective photoluminescence
decay time is observed and attributed to the state filling and
exciton thermalization between excited and ground states. A rate
equation model is also developed reproducing quite well the
observed exciton dynamics. 相似文献
5.
A. Weller P. Thomas J. Feldmann G. Peter E. O. Göbel 《Applied Physics A: Materials Science & Processing》1989,48(6):509-515
We present a phenomenological theoretical model to treat the trapping of carriers into quantum wells of semiconductor laser structures. We consider explicitely the transport within the barrier layers by solving the continuity equation with the appropriate boundary conditions taking into account surface recombination, radiative and nonradiative recombination in the barrier layers and trapping of carriers into the quantum wells. The experimental findings for the trapping dynamics in GaAs/AlGaAs quantum well structures can be consistently interpreted by the model calculations. 相似文献
6.
We consider the controlled switching of individual spins in a nonlinear, interacting spin chain by means of external magnetic fields. We show analytically and by full numerical simulations that stochastic switching is achievable when the driving fields are such that the underlying semi-classical dynamics is chaotic. On the basis of random matrix theory and the geometry of quantum evolution we confirm the quantum case to follow qualitatively the semi-classical behavior. 相似文献
7.
The effect of Jeans term in a multicomponent self-gravitating quantum magnetoplasma is investigated employing the quantum hydrodynamic (QHD) model. The effects of quantum Bohm potential and statistical terms as well as the ambient magnetic field are also investigated on both dust and ion dynamics driven waves in this Letter. We state the conditions that can drive the system unstable in the presence of Jeans term. The limiting cases are also presented. The present work may have relevance in the dense astrophysical environments where the self-gravitating effects are expected to play a pivotal role. 相似文献
8.
T. F. Albrecht J. H. H. Sandmann J. Feldmann W. Stolz E. O. Göbel H. Hillmer R. Lösch W. Schlapp 《Applied physics. B, Lasers and optics》1995,60(5):459-467
Femtosecond pulses of a collinearly pumped Optical Parametric Oscillator (OPO) are applied for investigations of the carrier dynamics in ternary and quaternary semiconductor quantum wells. The design and the specifications of the OPO are given in detail. We show that no measurable jitter exists between the pump pulses and the output pulses of the OPO. Therefore, it is possible to use the OPO and its pump laser for two-color experiments with a time resolution limited by the pulse lengths. We present and discuss results of transient four-wave mixing experiments on (InGa) As/InP quantum wells, and find a new kind of polarization-dependent quantum beat phenomenon. In addition, non-degenerate experiments on quantum wells from the quaternary (InGaAl) As material system, using two pulses at different wavelengths (one from the OPO and one from the pump laser), are discussed as a novel experimental technique to study carrier trapping into quantum wells. 相似文献
9.
We consider the nonlinear interactions between finite amplitude electron and ion plasma oscillations in a fermionic quantum plasma. Accounting for the quantum statistical electron pressure and the quantum Bohm potential, we derive a set of coupled nonlinear equations that govern the dynamics of modulated electron plasma oscillations (EPOs) in the presence of the nonlinear ion oscillations (NLIOs). We numerically study stationary solutions of our coupled nonlinear equations. We find that the quantum parameter H (equal to the ratio between the plasmonic and electron Fermi energy densities) introduces new features to the electron density and electric potential humps of localized NLIOs in the absence of EPOs. Furthermore, the nonlinear coupling between the EPOs and NLIOs gives rise to a new class of envelope solitons composed of bell shaped electric field envelope of the EPOs, which are trapped in the electron density hole (and an associated negative oscillatory electric potential) that is produced by the ponderomotive force of the EPOs. The knowledge of the localized plasmonic structures is of immense value for interpreting experimental observations in dense quantum plasmas. 相似文献
10.
11.
We study the dynamics of various branched spin chain systems. In such systems entanglement can be generated and distributed, providing an essential resource for teleportation or distributed quantum processing. We show in detail how simple operations can be employed at chosen times to change the subsequent dynamics of the branched spin chains, rendering the distributed entanglement more accessible. 相似文献
12.
We investigate the entanglement dynamics and Bell violation of three-qubit quantum states under an environment consisting of an XY spin chain with Dzyaloshinski–Moriya (DM) interaction. From the results, we find that the entanglement dynamics depends not only on the DM interaction, the magnetic field, and the anisotropy parameter but also on the number of the freedom degrees of the environment. The decoherence-free subspaces of our model have been identified and the Bell violation of quantum states is also discussed. 相似文献
13.
Josevi de S. Carvalho E. Passos Claudio Furtado Fernando Moraes 《The European Physical Journal C - Particles and Fields》2008,57(4):817-822
The relativistic quantum dynamics of a spinorial quantum particle in the presence of a chiral conical background is investigated.
We study the gravitational Berry geometric quantum phase acquired by a spin 1/2 particle in the chiral cosmic string spacetime.
We obtain the result that this phase depends on the global features of this spacetime. We also consider the case that a string
possesses an internal magnetic flux and obtain the geometric quantum phase in this case. The spacetime of multiple chiral
cosmic strings is considered and the relativistic Berry quantum phase is also obtained. 相似文献
14.
15.
Nikola Buri? 《Annals of Physics》2008,323(1):17-33
Schroedinger equation on a Hilbert space H, represents a linear Hamiltonian dynamical system on the space of quantum pure states, the projective Hilbert space PH. Separable states of a bipartite quantum system form a special submanifold of PH. We analyze the Hamiltonian dynamics that corresponds to the quantum system constrained on the manifold of separable states, using as an important example the system of two interacting qubits. The constraints introduce nonlinearities which render the dynamics nontrivial. We show that the qualitative properties of the constrained dynamics clearly manifest the symmetry of the qubits system. In particular, if the quantum Hamilton’s operator has not enough symmetry, the constrained dynamics is nonintegrable, and displays the typical features of a Hamiltonian dynamical system with mixed phase space. Possible physical realizations of the separability constraints are discussed. 相似文献
16.
17.
Time-Dependent Variational Approach to the Phonon Dispersion Relation of the Commensurate Quantum Frenkel-Kontorova Model 总被引:3,自引:0,他引:3
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The phonon dispersion relation of the commensurate quantum Frenkel-Kontorova model is studied by means of the time-dependent variational approach combined with a Hartree-type many-body trial wavefunction for the particles. The single-particle state is taken to be a frozen Jackiw-Kerman wavefunction. Under the condition of minimum uncertainty, equations of motion for the particle expectation values are derived to obtain the phonon dispersion relation. It is shown that the strength of the substrate potential and the phonon excitation gap are reduced due to the quantum fluctuations in comparison with those of the classical model. We also compare our results with those previously obtained by using the path-integral molecular dynamics. 相似文献
18.
We investigate the transition from integrability to chaos in a system built of usp(4) elements, both in the quantum case and in its classical limit, obtained using coherent states. This algebraic Hamiltonian consists in an integrable term plus a nonlinear perturbation, and we see that the level spacing distribution for the quantum system is well approximated by the Berry-Robnik-Brody distribution, and accordingly the classical limit displays mixed dynamics. 相似文献
19.
Zhi-Ming Zhan 《Physica A》2007,385(2):781-785
We propose a method for realizing the quantum controlled-NOT gate with a single resonant interaction in cavity QED. Our scheme only requires a single resonant interaction between two atoms and a cavity mode. Thus the scheme is very simple and the quantum dynamics operation can be realized at a high speed, which is important in view of decoherence. In addition, we also show that the gate can be realized in the ion trap system. 相似文献
20.
J.G. Peixoto de Faria 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):153-162
We present the general solutions for the classical and quantum
dynamics of the anharmonic oscillator coupled to a purely
diffusive environment. In both cases, these solutions are obtained by
the application of the Baker-Campbell-Hausdorff (BCH) formulas to
expand the evolution operator in an ordered product of
exponentials. Moreover, we obtain an expression for the Wigner
function in the quantum version of the problem. We observe that
the role played by diffusion is to reduce or to attenuate the
the characteristic quantum effects yielded by the nonlinearity,
as the appearance of coherent superpositions of quantum states
(Schr?dinger cat states) and revivals. 相似文献