52 research outputs found
Lower bounds for the polygon exploration problem
We improve the best known lower bound for the polygon exploration problem from 1.2071 to 1.2825
TWICE Dataset: Digital Twin of Test Scenarios in a Controlled Environment
Ensuring the safe and reliable operation of autonomous vehicles under adverse
weather remains a significant challenge. To address this, we have developed a
comprehensive dataset composed of sensor data acquired in a real test track and
reproduced in the laboratory for the same test scenarios. The provided dataset
includes camera, radar, LiDAR, inertial measurement unit (IMU), and GPS data
recorded under adverse weather conditions (rainy, night-time, and snowy
conditions). We recorded test scenarios using objects of interest such as car,
cyclist, truck and pedestrian -- some of which are inspired by EURONCAP
(European New Car Assessment Programme). The sensor data generated in the
laboratory is acquired by the execution of simulation-based tests in
hardware-in-the-loop environment with the digital twin of each real test
scenario. The dataset contains more than 2 hours of recording, which totals
more than 280GB of data. Therefore, it is a valuable resource for researchers
in the field of autonomous vehicles to test and improve their algorithms in
adverse weather conditions, as well as explore the simulation-to-reality gap.
The dataset is available for download at: https://twicedataset.github.io/site/Comment: 8 pages, 13 figures, submitted to IEEE Sensors Journa
Tunable interdot coupling in few-electron bilayer graphene double quantum dots
We present a highly controllable double quantum dot device based on bilayer
graphene. Using a device architecture of interdigitated gate fingers, we can
control the interdot tunnel coupling between 1 to 4 GHz and the mutual
capacitive coupling between 0.2 and 0.6 meV, independently of the charge
occupation of the quantum dots. The charging energy and hence the dot size
remains nearly unchanged. The tuning range of the tunnel coupling covers the
operating regime of typical silicon and GaAs spin qubit devices.Comment: 6 pages, 4 figure
Coherent Charge Oscillations in a Bilayer Graphene Double Quantum Dot
The coherent dynamics of a quantum mechanical two-level system passing
through an anti-crossing of two energy levels can give rise to
Landau-Zener-St\"uckelberg-Majorana (LZSM) interference. LZSM interference
spectroscopy has proven to be a fruitful tool to investigate charge noise and
charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer
graphene has developed as a promising platform to host highly tunable QDs
potentially useful for hosting spin and valley qubits. So far, in this system
no coherent oscillations have been observed and little is known about charge
noise in this material. Here, we report coherent charge oscillations and
charge decoherence times in a bilayer graphene double QD. The charge
decoherence times are measured independently using LZSM interference and photon
assisted tunneling. Both techniques yield average values in the range
of 400 to 500~ps. The observation of charge coherence allows to study the
origin and spectral distribution of charge noise in future experiments.Comment: Article: 9 pages, 5 figures; Supplementary Information: 11 pages, 9
figure
Generation of Realistic Synthetic Raw Radar Data for Automated Driving Applications using Generative Adversarial Networks
The main approaches for simulating FMCW radar are based on ray tracing, which
is usually computationally intensive and do not account for background noise.
This work proposes a faster method for FMCW radar simulation capable of
generating synthetic raw radar data using generative adversarial networks
(GAN). The code and pre-trained weights are open-source and available on
GitHub. This method generates 16 simultaneous chirps, which allows the
generated data to be used for the further development of algorithms for
processing radar data (filtering and clustering). This can increase the
potential for data augmentation, e.g., by generating data in non-existent or
safety-critical scenarios that are not reproducible in real life. In this work,
the GAN was trained with radar measurements of a motorcycle and used to
generate synthetic raw radar data of a motorcycle traveling in a straight line.
For generating this data, the distance of the motorcycle and Gaussian noise are
used as input to the neural network. The synthetic generated radar chirps were
evaluated using the Frechet Inception Distance (FID). Then, the Range-Azimuth
(RA) map is calculated twice: first, based on synthetic data using this GAN
and, second, based on real data. Based on these RA maps, an algorithm with
adaptive threshold and edge detection is used for object detection. The results
have shown that the data is realistic in terms of coherent radar reflections of
the motorcycle and background noise based on the comparison of chirps, the RA
maps and the object detection results. Thus, the proposed method in this work
has shown to minimize the simulation-to-reality gap for the generation of radar
data
Electron-hole crossover in gate-controlled bilayer graphene quantum dots
Electron and hole Bloch states in gapped bilayer graphene exhibit topological
orbital magnetic moments with opposite signs near the band edges, which allows
for tunable valley-polarization in an out-of-plane magnetic field. This
intrinsic property makes electron and hole quantum dots (QDs) in bilayer
graphene interesting for valley and spin-valley qubits. Here we show
measurements of the electron-hole crossover in a bilayer graphene QD,
demonstrating the opposite sign of the orbital magnetic moments associated with
the Berry curvature. Using three layers of metallic top gates, we independently
control the tunneling barriers of the QD while tuning the occupation from the
few-hole regime to the few-electron regime, crossing the displacement-field
controlled band gap. The band gap is around 25 meV, while the charging energies
of the electron and hole dots are between 3-5 meV. The extracted valley
g-factor is around 17 and leads to opposite valley polarization for electron
and hole states at moderate B-fields. Our measurements agree well with
tight-binding calculations for our device
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