955 research outputs found
Algebraic fidelity decay for local perturbations
From a reflection measurement in a rectangular microwave billiard with
randomly distributed scatterers the scattering and the ordinary fidelity was
studied. The position of one of the scatterers is the perturbation parameter.
Such perturbations can be considered as {\em local} since wave functions are
influenced only locally, in contrast to, e. g., the situation where the
fidelity decay is caused by the shift of one billiard wall. Using the
random-plane-wave conjecture, an analytic expression for the fidelity decay due
to the shift of one scatterer has been obtained, yielding an algebraic
decay for long times. A perfect agreement between experiment and theory has
been found, including a predicted scaling behavior concerning the dependence of
the fidelity decay on the shift distance. The only free parameter has been
determined independently from the variance of the level velocities.Comment: 4 pages, 5 figure
Fidelity decay for local perturbations: microwave evidence for oscillating decay exponents
We study fidelity decay in classically chaotic microwave billiards for a local, piston-like boundary perturbation. We experimentally verify a predicted non-monotonic cross-over from the Fermi Golden Rule to the escape-rate regime of the Loschmidt echo decay with increasing local boundary perturbation. In particular, we observe pronounced oscillations of the decay rate as a function of the piston position which quantitatively agree with corresponding theoretical results based on a refined semiclassical approach for local boundary perturbations
Distribution of the S-matrix in chaotic microwave cavities with direct processes and absorption
We quantify the presence of direct processes in the S-matrix of chaotic
microwave cavities with absorption in the one-channel case. To this end the
full distribution P_S(S) of the S-matrix, i.e. S=\sqrt{R}e^{i\theta}, is
studied in cavities with time-reversal symmetry for different antenna coupling
strengths T_a or direct processes. The experimental results are compared with
random-matrix calculations and with numerical simulations based on the
Heidelberg approach including absorption. The theoretical result is a
generalization of the Poisson kernel. The experimental and the numerical
distributions are in excellent agreement with random-matrix predictions for all
cases.Comment: 4 pages, 4 figure
Nodal domains in open microwave systems
Nodal domains are studied both for real and imaginary part
of the wavefunctions of an open microwave cavity and found to show the same
behavior as wavefunctions in closed billiards. In addition we investigate the
variation of the number of nodal domains and the signed area correlation by
changing the global phase according to
. This variation can be
qualitatively, and the correlation quantitatively explained in terms of the
phase rigidity characterising the openness of the billiard.Comment: 7 pages, 10 figures, submitted to PR
On the theory of cavities with point-like perturbations. Part II: Rectangular cavities
We consider an application of a general theory for cavities with point-like
perturbations for a rectangular shape. Hereby we concentrate on experimental
wave patterns obtained for nearly degenerate states. The nodal lines in these
patterns may be broken, which is an effect coming only from the experimental
determination of the patterns. These findings are explained within a framework
of the developed theory.Comment: 14 pages, 3 figure
Correlations of electromagnetic fields in chaotic cavities
We consider the fluctuations of electromagnetic fields in chaotic microwave
cavities. We calculate the transversal and longitudinal correlation function
based on a random wave assumption and compare the predictions with measurements
on two- and three-dimensional microwave cavities.Comment: Europhys style, 8 pages, 3 figures (included
Coherent Destruction of Photon Emission from a Single Molecule Source
The behavior of a single molecule driven simultaneously by a laser and by an
electric radio frequency field is investigated using a non-Hermitian
Hamiltonian approach. Employing the renormalization group method for
differential equations we calculate the average waiting time for the first
photon emission event to occur, and determine the conditions for the
suppression and enhancement of photon emission. An abrupt transition from
localization-like behavior to delocalization behavior is found.Comment: 5 pages, 4 figure
Diffractive orbits in the length spectrum of a 2D microwave cavity with a small scatterer
In a 2D rectangular microwave cavity dressed with one point-like scatterer, a
semiclassical approach is used to analyze the spectrum in terms of periodic
orbits and diffractive orbits. We show, both numerically and experimentally,
how the latter can be accounted for in the so-called length spectrum which is
retrieved from 2-point correlations of a finite range frequency spectrum.
Beyond its fundamental interest, this first experimental evidence of the role
played by diffractive orbits in the spectrum of an actual cavity, can be the
first step towards a novel technique to detect and track small defects in wave
cavities.Comment: 14 pages, format IO
Complete S-matrix in a microwave cavity at room temperature
We experimentally study the widths of resonances in a two-dimensional
microwave cavity at room temperature. By developing a model for the coupling
antennas, we are able to discriminate their contribution from those of ohmic
losses to the broadening of resonances. Concerning ohmic losses, we
experimentally put to evidence two mechanisms: damping along propagation and
absorption at the contour, the latter being responsible for variations of
widths from mode to mode due to its dependence on the spatial distribution of
the field at the contour. A theory, based on an S-matrix formalism, is given
for these variations. It is successfully validated through measurements of
several hundreds of resonances in a rectangular cavity.Comment: submitted to PR
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