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 $T_2^*$ 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 $T_2^*$ 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