5,779 research outputs found
Formation and interaction of resonance chains in the open 3-disk system
In ballistic open quantum systems one often observes that the resonances in
the complex-energy plane form a clear chain structure. Taking the open 3-disk
system as a paradigmatic model system, we investigate how this chain structure
is reflected in the resonance states and how it is connected to the underlying
classical dynamics. Using an efficient scattering approach we observe that
resonance states along one chain are clearly correlated while resonance states
of different chains show an anticorrelation. Studying the phase space
representations of the resonance states we find that their localization in
phase space oscillate between different regions of the classical trapped set as
one moves along the chains and that these oscillations are connected to a
modulation of the resonance spacing. A single resonance chain is thus no WKB
quantization of a single periodic orbits, but the structure of several
oscillating chains arises from the interaction of several periodic orbits. We
illuminate the physical mechanism behind these findings by combining the
semiclassical cycle expansion with a quantum graph model.Comment: 25 pages, 15 figure
Selective enhancement of topologically induced interface states in a dielectric resonator chain
The recent realization of topological phases in insulators and
superconductors has advanced the quest for robust quantum technologies. The
prospects to implement the underlying topological features controllably has
given incentive to explore optical platforms for analogous realizations. Here
we realize a topologically induced defect state in a chain of dielectric
microwave resonators and show that the functionality of the system can be
enhanced by supplementing topological protection with non-hermitian symmetries
that do not have an electronic counterpart. We draw on a characteristic
topological feature of the defect state, namely, that it breaks a sublattice
symmetry. This isolates the state from losses that respect parity-time
symmetry, which enhances its visibility relative to all other states both in
the frequency and in the time domain. This mode selection mechanism naturally
carries over to a wide range of topological and parity-time symmetric optical
platforms, including couplers, rectifiers and lasers.Comment: 5 pages, 4 figures, + supplementary information (3 pages, 4 figures
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
Scanning Fourier Spectroscopy: A microwave analog study to image transmission paths in quantum dots
We use a microwave cavity to investigate the influence of a movable absorbing
center on the wave function of an open quantum dot. Our study shows that the
absorber acts as a position-selective probe, which may be used to suppress
those wave function states that exhibit an enhancement of their probability
density near the region where the impurity is located. For an experimental
probe of this wave function selection, we develop a technique that we refer to
as scanning Fourier spectroscopy, which allows us to identify, and map out, the
structure of the classical trajectories that are important for transmission
through the cavity.Comment: 4 pages, 5 figure
The Calogero-Moser equation system and the ensemble average in the Gaussian ensembles
From random matrix theory it is known that for special values of the coupling
constant the Calogero-Moser (CM) equation system is nothing but the radial part
of a generalized harmonic oscillator Schroedinger equation. This allows an
immediate construction of the solutions by means of a Rodriguez relation. The
results are easily generalized to arbitrary values of the coupling constant. By
this the CM equations become nearly trivial.
As an application an expansion for in terms of eigenfunctions of
the CM equation system is obtained, where X and Y are matrices taken from one
of the Gaussian ensembles, and the brackets denote an average over the angular
variables.Comment: accepted by J. Phys.
Ballistic Electron Quantum Transport in Presence of a Disordered Background
Effect of a complicated many-body environment is analyzed on the electron
random scattering by a 2D mesoscopic open ballistic structure. A new mechanism
of decoherence is proposed. The temperature of the environment is supposed to
be zero whereas the energy of the incoming particle can be close to or
somewhat above the Fermi surface in the environment. The single-particle
doorway resonance states excited in the structure via external channels are
damped not only because of escape through such channels but also due to the
ulterior population of the long-lived environmental states. Transmission of an
electron with a given incoming through the structure turns out to be
an incoherent sum of the flow formed by the interfering damped doorway
resonances and the retarded flow of the particles re-emitted into the structure
by the environment. Though the number of the particles is conserved in each
individual event of transmission, there exists a probability that some part of
the electron's energy can be absorbed due to environmental many-body effects.
In such a case the electron can disappear from the resonance energy interval
and elude observation at the fixed transmission energy thus resulting
in seeming loss of particles, violation of the time reversal symmetry and, as a
consequence, suppression of the weak localization. The both decoherence and
absorption phenomena are treated within the framework of a unit microscopic
model based on the general theory of the resonance scattering. All the effects
discussed are controlled by the only parameter: the spreading width of the
doorway resonances, that uniquely determines the decoherence rateComment: 7 pages, 1 figure. The published version. A figure has been added;
the list of references has been improved. Some explanatory remarks have been
include
Effects of Sex and Hormonal Implant on Beef Carcass Characteristics and Palatability
A comparison of crossbred bulls, steers and heifers indicated that bulls have heavier carcasses, larger rib eyes and a more desirable yield grade. The USDA quality grade of the bulls was one-third of a grade lower than for the steers and heifers. The sensory and palatability characteristics showed no significant differences among axes. Implanted bulls as compared to non-implanted bulls showed more desirable taste panel scores for tenderness, juiciness and overall panel desirability
Self-Shielded Topological Receiver Protectors
Receiver protectors (RPs) shield sensitive electronics from high-power incoming signals that might damage them. Typical RP schemes range from simple fusing and PIN diodes to superconducting circuits and plasma cells-each having a variety of drawbacks ranging from unacceptable system downtime and self-destruction to significant insertion losses and power consumption. Here, we theoretically propose and experimentally demonstrate a unique self-shielding RP based on a coupled-resonator microwave waveguide, with a topological defect being inductively coupled to a diode. This RP utilizes a charge-conjugation-(C) symmetric resonant-defect mode that is robust against disorder and demonstrates high transmittance at low incident powers. When the incident power exceeds a critical value, a self-induced resonant trapping effect occurs, leading to a dramatic suppression of transmittance and a simultaneous increase of the reflectance close to unity. The proposed RP device is self-protected from overheating and electrical breakdown and can be utilized in radars, reflection altimeters, and a broad range of communication systems
- …