39 research outputs found
Spin-orbit-assisted electron pairing in 1D waveguides
Understanding and controlling the transport properties of interacting
fermions is a key forefront in quantum physics across a variety of experimental
platforms. Motivated by recent experiments in 1D electron channels written on
the / interface, we analyse how the
presence of different forms of spin-orbit coupling (SOC) can enhance electron
pairing in 1D waveguides. We first show how the intrinsic Rashba SOC felt by
electrons at interfaces such as / can be
reduced when they are confined in 1D. Then, we discuss how SOC can be
engineered, and show using a mean-field Hartree-Fock-Bogoliubov model that SOC
can generate and enhance spin-singlet and triplet electron pairing. Our results
are consistent with two recent sets of experiments [Briggeman et al.,
arXiv:1912.07164; Sci. Adv. 6, eaba6337 (2020)] that are believed to engineer
the forms of SOC investigated in this work, which suggests that metal-oxide
heterostructures constitute attractive platforms to control the collective spin
of electron bound states. However, our findings could also be applied to other
experimental platforms involving spinful fermions with attractive interactions,
such as cold atoms.Comment: 12 pages, 7 figure
Weakly-semi-supervised object detection in remotely sensed imagery
Deep learning for detecting objects in remotely sensed imagery can enable new
technologies for important applications including mitigating climate change.
However, these models often require large datasets labeled with bounding box
annotations which are expensive to curate, prohibiting the development of
models for new tasks and geographies. To address this challenge, we develop
weakly-semi-supervised object detection (WSSOD) models on remotely sensed
imagery which can leverage a small amount of bounding boxes together with a
large amount of point labels that are easy to acquire at scale in geospatial
data. We train WSSOD models which use large amounts of point-labeled images
with varying fractions of bounding box labeled images in FAIR1M and a wind
turbine detection dataset, and demonstrate that they substantially outperform
fully supervised models trained with the same amount of bounding box labeled
images on both datasets. Furthermore, we find that the WSSOD models trained
with 2-10x fewer bounding box labeled images can perform similarly to or
outperform fully supervised models trained on the full set of bounding-box
labeled images. We believe that the approach can be extended to other remote
sensing tasks to reduce reliance on bounding box labels and increase
development of models for impactful applications.Comment: Tackling Climate Change with Machine Learning at NeurIPS 202
CloudTracks: A Dataset for Localizing Ship Tracks in Satellite Images of Clouds
Clouds play a significant role in global temperature regulation through their
effect on planetary albedo. Anthropogenic emissions of aerosols can alter the
albedo of clouds, but the extent of this effect, and its consequent impact on
temperature change, remains uncertain. Human-induced clouds caused by ship
aerosol emissions, commonly referred to as ship tracks, provide visible
manifestations of this effect distinct from adjacent cloud regions and
therefore serve as a useful sandbox to study human-induced clouds. However, the
lack of large-scale ship track data makes it difficult to deduce their general
effects on cloud formation. Towards developing automated approaches to localize
ship tracks at scale, we present CloudTracks, a dataset containing 3,560
satellite images labeled with more than 12,000 ship track instance annotations.
We train semantic segmentation and instance segmentation model baselines on our
dataset and find that our best model substantially outperforms previous
state-of-the-art for ship track localization (61.29 vs. 48.65 IoU). We also
find that the best instance segmentation model is able to identify the number
of ship tracks in each image more accurately than the previous state-of-the-art
(1.64 vs. 4.99 MAE). However, we identify cases where the best model struggles
to accurately localize and count ship tracks, so we believe CloudTracks will
stimulate novel machine learning approaches to better detect elongated and
overlapping features in satellite images. We release our dataset openly at
{zenodo.org/records/10042922}.Comment: 11 pages, 5 figures, submitted to Journal of Machine Learning
Researc
One-dimensional Kronig-Penney superlattices at the LaAlO/SrTiO interface
The paradigm of electrons interacting with a periodic lattice potential is
central to solid-state physics. Semiconductor heterostructures and ultracold
neutral atomic lattices capture many of the essential properties of 1D
electronic systems. However, fully one-dimensional superlattices are highly
challenging to fabricate in the solid state due to the inherently small length
scales involved. Conductive atomic-force microscope (c-AFM) lithography has
recently been demonstrated to create ballistic few-mode electron waveguides
with highly quantized conductance and strongly attractive electron-electron
interactions. Here we show that artificial Kronig-Penney-like superlattice
potentials can be imposed on such waveguides, introducing a new superlattice
spacing that can be made comparable to the mean separation between electrons.
The imposed superlattice potential "fractures" the electronic subbands into a
manifold of new subbands with magnetically-tunable fractional conductance (in
units of ). The lowest plateau, associated with ballistic
transport of spin-singlet electron pairs, is stable against de-pairing up to
the highest magnetic fields explored ( T). A 1D model of the system
suggests that an engineered spin-orbit interaction in the superlattice
contributes to the enhanced pairing observed in the devices. These findings
represent an important advance in the ability to design new families of quantum
materials with emergent properties, and mark a milestone in the development of
a solid-state 1D quantum simulation platform
CheXpert: A Large Chest Radiograph Dataset with Uncertainty Labels and Expert Comparison
Large, labeled datasets have driven deep learning methods to achieve
expert-level performance on a variety of medical imaging tasks. We present
CheXpert, a large dataset that contains 224,316 chest radiographs of 65,240
patients. We design a labeler to automatically detect the presence of 14
observations in radiology reports, capturing uncertainties inherent in
radiograph interpretation. We investigate different approaches to using the
uncertainty labels for training convolutional neural networks that output the
probability of these observations given the available frontal and lateral
radiographs. On a validation set of 200 chest radiographic studies which were
manually annotated by 3 board-certified radiologists, we find that different
uncertainty approaches are useful for different pathologies. We then evaluate
our best model on a test set composed of 500 chest radiographic studies
annotated by a consensus of 5 board-certified radiologists, and compare the
performance of our model to that of 3 additional radiologists in the detection
of 5 selected pathologies. On Cardiomegaly, Edema, and Pleural Effusion, the
model ROC and PR curves lie above all 3 radiologist operating points. We
release the dataset to the public as a standard benchmark to evaluate
performance of chest radiograph interpretation models.
The dataset is freely available at
https://stanfordmlgroup.github.io/competitions/chexpert .Comment: Published in AAAI 201
Tunable electron-electron interactions in LaAlO3/SrTiO3 nanostructures
The interface between the two complex oxides LaAlO3 and SrTiO3 has remarkable
properties that can be locally reconfigured between conducting and insulating
states using a conductive atomic force microscope. Prior investigations of
sketched quantum dot devices revealed a phase in which electrons form pairs,
implying a strongly attractive electron-electron interaction. Here, we show
that these devices with strong electron-electron interactions can exhibit a
gate-tunable transition from a pair-tunneling regime to a single-electron
(Andreev bound state) tunneling regime where the interactions become repulsive.
The electron-electron interaction sign change is associated with a Lifshitz
transition where the dxz and dyz bands start to become occupied. This
electronically tunable electron-electron interaction, combined with the
nanoscale reconfigurability of this system, provides an interesting starting
point towards solid-state quantum simulation.Comment: 25 pages, 7 figure