1,785 research outputs found
Bipolaronic blockade effect in quantum dots with negative charging energy
We investigate single-electron transport through quantum dots with negative
charging energy induced by a polaronic energy shift. For weak dot-lead tunnel
couplings, we demonstrate a bipolaronic blockade effect at low biases which
suppresses the oscillating linear conductance, while the conductance resonances
under large biases are enhanced. Novel conductance plateau develops when the
coupling asymmetry is introduced, with its height and width tuned by the
coupling strength and external magnetic field. It is further shown that the
amplitude ratio of magnetic-split conductance peaks changes from 3 to 1for
increasing coupling asymmetry. Though we demonstrate all these transport
phenomena in the low-order single-electron tunneling regime, they are already
strikingly different from the usual Coulomb blockade physics and are easy to
observe experimentally.Comment: 6 pages, 5 figure
The Brain Metabolites Within Cerebellum of Native Chinese Speakers who are Using the Traditional Logographic Reading and Writing Systems - A Magnetic Resonance Spectroscopy Approach to Dyslexia
On Investigating the Conservative Property of Score-Based Generative Models
Existing Score-based Generative Models (SGMs) can be categorized into
constrained SGMs (CSGMs) or unconstrained SGMs (USGMs) according to their
parameterization approaches. CSGMs model probability density functions as
Boltzmann distributions, and assign their predictions as the negative gradients
of some scalar-valued energy functions. On the other hand, USGMs employ
flexible architectures capable of directly estimating scores without the need
to explicitly model energy functions. In this paper, we demonstrate that the
architectural constraints of CSGMs may limit their modeling ability. In
addition, we show that USGMs' inability to preserve the property of
conservativeness may lead to degraded sampling performance in practice. To
address the above issues, we propose Quasi-Conservative Score-based Generative
Models (QCSGMs) for keeping the advantages of both CSGMs and USGMs. Our
theoretical derivations demonstrate that the training objective of QCSGMs can
be efficiently integrated into the training processes by leveraging the
Hutchinson trace estimator. In addition, our experimental results on the
CIFAR-10, CIFAR-100, ImageNet, and SVHN datasets validate the effectiveness of
QCSGMs. Finally, we justify the advantage of QCSGMs using an example of a
one-layered autoencoder
Training Energy-Based Normalizing Flow with Score-Matching Objectives
In this paper, we establish a connection between the parameterization of
flow-based and energy-based generative models, and present a new flow-based
modeling approach called energy-based normalizing flow (EBFlow). We demonstrate
that by optimizing EBFlow with score-matching objectives, the computation of
Jacobian determinants for linear transformations can be entirely bypassed. This
feature enables the use of arbitrary linear layers in the construction of
flow-based models without increasing the computational time complexity of each
training iteration from to for an
-layered model that accepts -dimensional inputs. This makes the training
of EBFlow more efficient than the commonly-adopted maximum likelihood training
method. In addition to the reduction in runtime, we enhance the training
stability and empirical performance of EBFlow through a number of techniques
developed based on our analysis on the score-matching methods. The experimental
results demonstrate that our approach achieves a significant speedup compared
to maximum likelihood estimation, while outperforming prior efficient training
techniques with a noticeable margin in terms of negative log-likelihood (NLL)
Movable Fiber-Integrated Hybrid Plasmonic Waveguide on Metal Film
A waveguide structure consisting of a tapered nanofiber on a metal film is
proposed and analyzed to support highly localized hybrid plasmonic modes. The
hybrid plasmonic mode can be efficiently excited through the in-line tapered
fiber based on adiabatic conversion and collected by the same fiber, which is
very convenient in the experiment. Due to the ultrasmall mode area of plasmonic
mode, the local electromagnetic field is greatly enhanced in this movable
waveguide, which is potential for enhanced coherence light emitter
interactions, such as waveguide quantum electrodynamics, single emitter
spectrum and nonlinear optics
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