Electrical operation of planar Ge hole spin qubits in an in-plane magnetic field

In this work we present a comprehensive theory of spin physics in planar Ge hole quantum dots in an in-plane magnetic field, where the orbital terms play a dominant role in qubit physics, and provide a brief comparison with experimental measurements of the angular dependence of electrically driven spin resonance. We focus the theoretical analysis on electrical spin operation, phonon-induced relaxation, and the existence of coherence sweet spots. We find that the choice of magnetic field orientation makes a substantial difference for the properties of hole spin qubits. Furthermore, although the Schrieffer-Wolff approximation can describe electron dipole spin resonance (EDSR), it does not capture the fundamental spin dynamics underlying qubit coherence. Specifically, we find that: (i) EDSR for in-plane magnetic fields varies non-linearly with the field strength and weaker than for perpendicular magnetic fields; (ii) The EDSR Rabi frequency is maximized when the a.c. electric field is aligned parallel to the magnetic field, and vanishes when the two are perpendicular; (iii) The Rabi ratio $T_1/T_\pi$, i.e. the number of EDSR gate operation per unit relaxation time, is expected to be as large as $5{\times}10^5$ at the magnetic fields used experimentally; (iv) The orbital magnetic field terms make the in-plane $g$-factor strongly anisotropic in a squeezed dot, in excellent agreement with experimental measurements; (v) The coherence sweet spots do not exist in an in-plane magnetic field, as the orbital magnetic field terms expose the qubit to all components of the defect electric field. These findings will provide a guideline for experiments to design ultrafast, highly coherent hole spin qubits in Ge

Exact Results for a Kondo Problem in One Dimensional t-J Model

We propose an integrable Kondo problem in a one-dimensional (1D) $t-J$ model. With the open boundary condition of the wave functions at the impurity sites, the model can be exactly solved via Bethe ansatz for a class of $J_{R,L}$ (Kondo coupling constants) and $V_{L,R}$ (impurity potentials) parametrized by a single parameter $c$. The integrable value of $J_{L,R}$ runs from negative infinity to positive infinity, which allows us to study both the ferromagnetic Kondo problem and antiferromagnetic Kondo problem in a strongly correlated electron system. Generally, there is a residual entropy for the ground state, which indicates a typical non-Fermi liquid behavior.Comment: 5 pages Revtex, no figure

Detection and Implementation of Driver’s Seatbelt Based on FPGA

Abstract In this paper, the driver’s seatbelt detection algorithm is transplanted to the PYNQ embedded platform of XILINX to meet the technical requirements of automatic identification and detection of whether the driver wears a seatbelt or not. In this paper, aiming at the characteristics of the hardware of the FPGA, the driver’s seatbelt detection algorithm is realized by IP core from XILINX open source. Vehicle detection is realized by using YOLO object detection algorithm with 3 bit weight and 1 bit activation, and driver’s seatbelt classification is realized by using binary model with 1 bit weight and 1 bit activation. On the PYNQ embedded hardware of XILINX, the acceleration of the algorithm is realized by calling the hardware of FPGA on the ARM side

Video Imprint Segmentation for Temporal Action Detection in Untrimmed Videos

We propose a temporal action detection by spatial segmentation framework, which simultaneously categorize actions and temporally localize action instances in untrimmed videos. The core idea is the conversion of temporal detection task into a spatial semantic segmentation task. Firstly, the video imprint representation is employed to capture the spatial/temporal interdependences within/among frames and represent them as spatial proximity in a feature space. Subsequently, the obtained imprint representation is spatially segmented by a fully convolutional network. With such segmentation labels projected back to the video space, both temporal action boundary localization and per-frame spatial annotation can be obtained simultaneously. The proposed framework is robust to variable lengths of untrimmed videos, due to the underlying fixed-size imprint representations. The efficacy of the framework is validated in two public action detection datasets

The dispersion, stability, and resuspension of C in environmental water matrices.

Environmental waters cover a range of water quality characteristics which could greatly affect the behavior and fate of C60 in the aquatic environment. In this study, the dispersion and stability of C60 in several environmental water matrices during a 70-day extended mixing period were investigated to better understand its environmental behavior and fate in environmental waters. Relatively stable nanoscale aggregates in water (aqu/nC60) could be formed in wastewater influent, while unstable suspensions were obtained in river water, wastewater effluent, seawater, and estuarine water. During the extended mixing under sunlight, oxygen-containing moieties were produced on the surface of the C60 aggregates, independent of the kind of environmental water matrices. Once the mixed system went under quiescent condition, aggregation and sedimentation of aqu/nC60 occurred. However, an extremely short-time disturbance could easily resuspend the C60 aggregates deposited and increase the concentration of aqu/nC60 in the overlying water column. Therefore, the effects of resuspension should be considered when investigating the environmental behavior and fate of C60