共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Casado T. Marshall R. Risco-Delgado E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):109-119
We continue the study of parametric down conversion within the framework of the Wigner representation, by using a Maxwellian
approach developed in a recent paper [A. Casado et al., Eur. Phys. J. D 11, 465 (2000)]. This gives a mechanism, inside the crystal, for the production of the down-converted radiation. We obtain the
electric field to second order in the coupling constant by using the Green's function method, and compare our treatment with
the standard Hamiltonian approach. The spectrum of the down-converted radiation is calculated as a function of the parameters
of the nonlinear crystal (in particular the length) and the radius of the pumping beam.
Received 15 May 2000 相似文献
2.
F. Selva D. Weinmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):137-148
A Wigner crystal structure of the electronic ground state is induced by strong Coulomb interactions at low temperature in
clean or disordered two-dimensional (2d) samples. For fermions on a mesoscopic disordered 2d lattice, being closed to a torus,
we study the persistent current in the regime of strong interaction at zero temperature. We perform a perturbation expansion
starting from the Wigner crystal limit which yields power laws for the dependence of the persistent current on the interaction
strength. The sign of the persistent current in the strong interaction limit is independent of the disorder realization and
strength. It depends only on the electro-statically determined configuration of the particles in the Wigner crystal.
Received 14 March 2000 相似文献
3.
S. Mancini A. Gatti L. Lugiato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):499-508
We study the noiseless amplification of an optical image by means of a confocal cavity containing a parametric medium. We
demonstrate, in the ideal situation, the possibility of preserving the signal-to-noise ratio while amplifying uniformly the
entire image. Some specific effects, which may degrade the performances of the scheme, are taken into account.
Received 23 March 2000 相似文献
4.
S. Fratini P. Quémerais 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):99-113
The melting of a Wigner Crystal of electrons placed into a host polar material is examined as a function of the density and
the temperature. When the coupling to the longitudinal optical modes of the host medium is turned on, the WC is progressively
transformed into a polaronic Wigner crystal. We estimate the critical density for crystal melting at zero temperature using
the Lindeman criterion. We show that above a certain critical value of the Fr?hlich electron-phonon coupling, the melting
towards a quantum liquid of polarons is not possible, and the insulator-to-metal transition is driven by the ionization of
the polarons (polaron dissociation). The phase diagram at finite temperature is obtained by making use of the same Lindeman
criterion. Results are also provided in the case of an anisotropic electron band mass, showing that the scenario of polaron
dissociation can be relevant in anisotropic compounds such as the superconducting cuprates at rather moderate e-ph couplings.
Received 13 August 1999 相似文献
5.
Spatial and temporal properties of parametric fluorescence around degeneracy in a type I LBO crystal
F. Devaux E. Lantz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):117-124
We present a theoretical and experimental study of the spatio-temporal properties of the spontaneous parametric emission generated
in a type I LBO crystal around degeneracy. The number of quasi-phase-matched modes is shown to be equal to the number of spatio-temporal
degrees of freedom of the image that can be parametrically amplified. From this number, we demonstrate the possibility of
predicting the total number of photons generated by parametric fluorescence. Correlation is observed between spatial intensity
fluctuations corresponding to pairs of signal-idler modes.
Received 18 February 1999 and Received in final form 9 June 1999 相似文献
6.
C.M. Granzow A. Liebman G. Mahler 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(1):131-142
Continuous measurement models are conveniently based on master equations specified by the respective Hamiltonian and appropriate
environment operators. As demonstrated by stochastic unraveling, the latter specify the dynamical process rather than static
detection modes. We show that certain environment operators acting on a simple system may, in fact, require extended networks
for implementation: Their Hamilton parameters re-appear in the effective environment operators of the reduced model. The resulting
quantum trajectories typically involve competing paths, which may give rise to different fluctuation and noise properties
even when the corresponding ensemble behavior is practically the same.
Received: 21 July 1997 / Received in final form: 10 November 1997 / Accepted: 27 October 1997 相似文献
7.
S.A. Mikhailov K. Ziegler 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):117-120
A floating Wigner crystal differs from the standard one by a spatial averaging over positions of the Wigner-crystal lattice.
It has the same internal structure as the fixed crystal, but contrary to it, takes into account rotational and/or translational
symmetry of the underlying jellium background. We study properties of a floating Wigner molecule in few-electron spin-polarized
quantum dots, and show that the floating solid has the lower energy than the standard Wigner crystal with fixed lattice points.
We also argue that internal rotational symmetry of individual dots can be broken in arrays of quantum dots, due to degenerate
ground states and inter-dot Coulomb coupling.
Received 12 September 2001 / Received in final form 24 April 2002 Published online 9 July 2002 相似文献
8.
S. Yuan J.-Y. Gao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):267-272
A new scheme of the influence of quantum interference on the spontaneous emission in a coherently driven three-level medium
is presented in this paper. The results are the same with that discussed by [S.-Y. Zhu, L.M. Narducci, M.O. Scully, Phys.
Rev. A 52, 4791 (1995)] under resonance conditions, but they are different when the driven field is detuned.
Received 8 September 1999 and Received in final form 13 January 2000 相似文献
9.
We propose a scheme for direct measurement of the Wigner function for a cavity mode. In the scheme the cavity field resonantly interacts with an atomic ensemble. Under certain conditions, the state of the cavity mode is transferred to the atomic system. After a displacement the measurement of the parity of the atomic excitation number directly yields the Wigner function of the initial state of the cavity mode. 相似文献
10.
D. Braun 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):3-12
I investigate the propagator of the Wigner function for a dissipative chaotic quantum map. I show that a small amount of dissipation
reduces the propagator of sufficiently smooth Wigner functions to its classical counterpart, the Frobenius-Perron operator,
if . Several consequences arise: the Wigner transform of the invariant density matrix is a smeared out version of the classical
strange attractor; time dependent expectation values and correlation functions of observables can be evaluated via hybrid quantum-classical formulae in which the quantum character enters only via the initial Wigner function. If a classical phase-space distribution is chosen for the latter or if the map is iterated sufficiently
many times the formulae become entirely classical, and powerful classical trace formulae apply.
Received 7 October 1999 相似文献
11.
Wang Kaige A. Sinatra L.A. Lugiato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):339-349
We present a simple method, based on the quantum regression theorem, to calculate the quantum correlation spectra for two
optical beams in the linearized fluctuation regime. As an application, we discuss the dynamical instability, the squeezing
spectra and the QND properties of a crossed Kerr-type dispersive model.
Received 30 August 1999 and Received in final form 4 July 2000 相似文献
12.
S.-y. Xie Y.-p. Yang X. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):129-143
We study the spontaneous emission properties of a V-type three-level atom embedded in a photonic crystal with the anisotropic
dispersion relation. We show that the localized field can disappear and the diffusion field can become intense in some regions.
This originates from no singularity of the density of states. The quantum interference leads to oscillatory, quasi-oscillatory
or complete decay behavior of population. The complete decay can also be realized in certain condition without depending on
the initial state.
Received 9 April 2000 and Received in final form 1st August 2000 相似文献
13.
We present a proposal to measure field states for traveling modes. The scheme leads, in a simple and direct way, to the characteristic function of the state, yielding the determination of the Wigner function without a demanding data analysis. We employ a Mach-Zehnder interferometer including an auxiliary nonlinear medium in one arm. Analogies with other proposals to reconstruct states of stationary fields and trapped atoms are discussed. 相似文献
14.
The excited squeezed light (ESL) can be the outcome of interaction between squeezed light probe and excited atom, which can explore the status and the structure of the atom. We calculate the Wigner function and tomogram of ESL that may be comparable to the experimental measurement of quadrature-amplitude distribution for the light field obtained using balanced homodyne detection. The method of calculation seems new. 相似文献
15.
S. Fratini P. Quémerais 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):41-49
We consider a three dimensional Wigner crystal of electrons lying in a host ionic dielectric. Owing to their interaction with
the lattice polarization, each localized electron forms a polaron. We study the collective excitations of such a polaronic
Wigner crystal at zero temperature, taking into account the quantum fluctuations of the polarization within the Feynman harmonic
approximation. We show that, contrary to the ordinary electron crystal, the system undergoes a polarization catastrophe when
the density is increased. An optical signature of this instability is derived, whose trend agrees with the experiments carried
out in Nd-based cuprates.
Received 4 July 2002 Published online 17 September 2002 相似文献
16.
C. Wiele F. Haake K. Rzażewski 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(3):405-409
We solve the superradiant laser model in two limiting cases. First the stationary low-pumping regime is considered where a
first-order phase transition in the semiclassical solution occurs. This discontinuity is smeared out in the quantum regime.
Second, we solve the model in the non-stationary regime where we find a temporally periodic solution. For a certain parameter
range well-separated pulses may occur.
Received: 19 June 1998 / Accepted: 19 October 1998 相似文献
17.
M. Gangl H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):29-40
We develop quantum models for the combined external and internal motion of atoms in a strongly coupled driven cavity mode
including the transverse degrees of freedom. Using a simplified Gaussian mode function we determine the parameter regimes
and prospects of 3D cooling and confinement of one or two atoms in the cavity field. Analysing the field dynamics for slow
atoms traversing the cavity, we show that the spectrum of the transmitted and spontaneously scattered light contains ample
information on the motional dynamics of the atom and can be nicely used to investigate the cooling properties of the system.
Including several atoms in the dynamics we show how motional correlations build up by the common interaction with the cavity
field. This can be looked upon as collisions at far distance and can be monitored via the transmitted field dynamics.
Received 5 March 1999 and Received in final form 4 May 1999 相似文献
18.
P. Fröbrich P.J. Jensen P.J. Kuntz A. Ecker 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):579-594
The field-induced reorientation of the magnetization of ferromagnetic films is treated within the framework of many-body Green's
function theory by considering all components of the magnetization. We present a new method for the calculation of expectation
values in terms of the eigenvalues and eigenvectors of the equations of motion matrix for the set of Green's functions. This
formulation allows a straightforward extension of the monolayer case to thin films with many layers and for arbitrary spin
and moreover provides a practicable procedure for numerical computation. The model Hamiltonian includes a Heisenberg term,
an external magnetic field, a second-order uniaxial single-ion anisotropy, and the magnetic dipole-dipole coupling. We utilize
the Tyablikov (RPA) decoupling for the exchange interaction terms and the Anderson-Callen decoupling for the anisotropy terms.
The dipole coupling is treated in the mean-field approximation, a procedure which we demonstrate to be a sufficiently good
approximation for realistic coupling strengths. We apply the new method to monolayers with spin and to multilayer systems with S=1. We compare some of our results to those where mean-field theory (MFT) is applied to all interactions, pointing out some
significant differences.
Received 19 June 2000 and Received in final form 2 August 2000 相似文献
19.
In this paper, we give a detailed derivation process for the Wigner function (WF) of an arbitrary photon-catalyzed optical coherent state (APCOCS), which can be generated via interference between coherent and Fock states using quantum catalysis. We find that the WF is non-Gaussian and is related to the two-variable Hermite polynomial of the relative parameters, such as the coherent field strength, the number of catalyst photons and the control ratio of the beam splitter. It showed that the APCOCS created a wide range of nonclassical properties. 相似文献
20.
E. Lantz F. Devaux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):93-98
We study the properties of the spatial fluctuations in the far-field parametric fluorescence output of a type 1 degenerate
traveling-wave parametric amplifier. Results of a semi-classical simulation are compared with experiments in a LBO crystal.
This simulation is then used to predict amplified images of a continuous background, in a phase-sensitive as well as in a
phase-insensitive configuration.
Received 12 March 2001 相似文献