Structural Embedding of Syntactic Trees for Machine Comprehension

Deep neural networks for machine comprehension typically utilizes only word or character embeddings without explicitly taking advantage of structured linguistic information such as constituency trees and dependency trees. In this paper, we propose structural embedding of syntactic trees (SEST), an algorithm framework to utilize structured information and encode them into vector representations that can boost the performance of algorithms for the machine comprehension. We evaluate our approach using a state-of-the-art neural attention model on the SQuAD dataset. Experimental results demonstrate that our model can accurately identify the syntactic boundaries of the sentences and extract answers that are syntactically coherent over the baseline methods

Dissimilarity measures for content-based image retrieval

Dissimilarity measurement plays a crucial role in content-based image retrieval. In this paper, 16 core dissimilarity measures are introduced and evaluated. We carry out a systematic performance comparison on three image collections, Corel, Getty and Trecvid2003, with 7 different feature spaces. Two search scenarios are considered: single image queries based on the vector space model, and multi-image queries based on k-nearest neighbours search. A number of observations are drawn, which will lay a foundation for developing more effective image search technologies

Polarization-based cyclic weak value metrology for angular velocity measurement

Weak value has been proved to amplify the detecting changes of the meters at the cost of power due to post-selection. Previous power-recycling schemes enable the failed post-selection photons to be reselected repeatedly, thus surpassing the upper noise limit and improving the precision of interferometric systems. Here we introduce three cyclic methods to improve the sensitivity of polarization-based weak-value-based angular velocity measurement: power-, signal- and dual-recycling schemes. By inserting one or two partially transmitting mirrors inside the system, both the power and precision of detected signals are greatly enhanced, and the dual-recycling scheme has wider optimal region than that of power- or signal-recycling schemes. Compared to non-polarization schemes, polarization-based schemes enjoy lower optical loss and unique cyclic directions. These reduce the crosstalk among different paths of light and, theoretically, eliminate the walk-off effect, thus towering in both theoretical performance and application.Comment: 7 pages, 3 figure

Half-Quantized Hall Effect at the Parity-Invariant Fermi Surface

Condensed matter realization of a single Dirac cone of fermions in two dimensions is a long-standing issue. Here we report the discovery of a single gapless Dirac cone of half-quantized Hall conductance in a magnetically-doped topological insulator heterostructure. It demonstrates that the Hall conductance is half-quantized in the unit e^{2}/h when the parity symmetry is invariant near the Fermi surface. The gapless Dirac point is stable and protected by the local parity symmetry and the topologically nontrivial band structure of the topological insulator. The one-half Hall conductance observed in a recent experiment [Mogi et al, Nat. Phys. 18, 390 (2022)] is attributed to the existence of the gapless Dirac cone. The results suggest a condensed matter realization of a topological phase with a one-half topological invariant.Comment: 6 pages with 4 figure

Improving mobility of silicon metal-oxide-semiconductor devices for quantum dots by high vacuum activation annealing

To improve mobility of fabricated silicon metal-oxide-semiconductor (MOS) quantum devices, forming gas annealing is a common method used to mitigate the effects of disorder at the Si/SiO2 interface. However, the importance of activation annealing is usually ignored. Here, we show that a high vacuum environment for implantation activation is beneficial for improving mobility compared to nitrogen atmosphere. Low-temperature transport measurements of Hall bars show that peak mobility can be improved by a factor of two, reaching 1.5 m^2/(Vs) using high vacuum annealing during implantation activation. Moreover, the charge stability diagram of a single quantum dot is mapped, with no visible disturbance caused by disorder, suggesting possibility of fabricating high-quality quantum dots on commercial wafers. Our results may provide valuable insights into device optimization in silicon-based quantum computing.Comment: 13 pages, 4 figure

Theory of d+idd + id Second-Order Topological Superconductors

Topological superconductors are a class of unconventional superconducting materials featuring sub-gap zero-energy Majorana bound modes that hold promise as a building block for topological quantum computing. In this work, we study the realization of second-order topology that defines anomalous gapless boundary modes in a two-orbital superconductor with spin-orbital couplings. We reveal a time-reversal symmetry-breaking second-order topological superconducting phase with $d+id$-wave orbital-dependent paring without the need for the external magnetic field. Remarkably, this orbital-active $d$-wave paring gives rise to anomalous zero-energy Majorana corner modes, which is in contrast to conventional chiral $d$-wave pairing, accommodating one-dimensional Majorana edge modes. Our work not only reveals a unique mechanism of time-reversal symmetry breaking second-order topological superconductors but also bridges the gap between second-order topology and orbital-dependent pairings.Comment: 5+ pages, 5 figure

Traffic experiment reveals the nature of car-following

As a typical self-driven many-particle system far from equilibrium, traffic flow exhibits diverse fascinating non-equilibrium phenomena, most of which are closely related to traffic flow stability and specifically the growth/dissipation pattern of disturbances. However, the traffic theories have been controversial due to a lack of precise traffic data. We have studied traffic flow from a new perspective by carrying out large-scale car-following experiment on an open road section, which overcomes the intrinsic deficiency of empirical observations. The experiment has shown clearly the nature of car-following, which runs against the traditional traffic flow theory. Simulations show that by removing the fundamental notion in the traditional car-following models and allowing the traffic state to span a two-dimensional region in velocity-spacing plane, the growth pattern of disturbances has changed qualitatively and becomes qualitatively or even quantitatively in consistent with that observed in the experiment.Comment: 24 pages, 7 figure