237 research outputs found
Irreversible quantum graphs
Irreversibility is introduced to quantum graphs by coupling the graphs to a
bath of harmonic oscillators. The interaction which is linear in the harmonic
oscillator amplitudes is localized at the vertices. It is shown that for
sufficiently strong coupling, the spectrum of the system admits a new continuum
mode which exists even if the graph is compact, and a {\it single} harmonic
oscillator is coupled to it. This mechanism is shown to imply that the quantum
dynamics is irreversible. Moreover, it demonstrates the surprising result that
irreversibility can be introduced by a "bath" which consists of a {\it single}
harmonic oscillator
Fingerprints of classical diffusion in open 2D mesoscopic systems in the metallic regime
We investigate the distribution of the resonance widths
and Wigner delay times for scattering from two-dimensional
systems in the diffusive regime. We obtain the forms of these distributions
(log-normal for large and small , and power law in the
opposite case) for different symmetry classes and show that they are determined
by the underlying diffusive classical dynamics. Our theoretical arguments are
supported by extensive numerical calculations.Comment: 7 pages, 3 figure
Unidirectional Lasing Emerging from Frozen Light in Non-Reciprocal Cavities
We introduce a class of unidirectional lasing modes associated with the
frozen mode regime of non-reciprocal slow-wave structures. Such asymmetric
modes can only exist in cavities with broken time-reversal and space inversion
symmetries. Their lasing frequency coincides with a spectral stationary
inflection point of the underlying passive structure and is virtually
independent of its size. These unidirectional lasers can be indispensable
components of photonic integrated circuitry.Comment: 5 pages, 3 figure
Waveguide photonic limiters based on topologically protected resonant modes
We propose a concept of chiral photonic limiters utilising topologically
protected localised midgap defect states in a photonic waveguide. The chiral
symmetry alleviates the effects of structural imperfections and guaranties a
high level of resonant transmission for low intensity radiation. At high
intensity, the light-induced absorption can suppress the localised modes, along
with the resonant transmission. In this case the entire photonic structure
becomes highly reflective within a broad frequency range, thus increasing
dramatically the damage threshold of the limiter. Here we demonstrate
experimentally the principle of operation of such photonic structures using a
waveguide consisting of coupled dielectric microwave resonators.Comment: 6 pages, 4 figure
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