Characterizations and Quantifications of Macroscopic Quantumness and Its Implementations using Optical Fields

We present a review and discussions on characterizations and quantifications of macroscopic quantum states as well as their implementations and applications in optical systems. We compare and criticize different measures proposed to define and quantify macroscopic quantum superpositions and extend such comparisons to several types of optical quantum states actively considered for experimental implementations within recent research topics.Comment: 13 pages, 2 figures, references added, review article to be published in the Special Issue of Optics Communications on Macroscopic Quantumness: Theory and Applications in Optical Science

Production of entanglement with highly-mixed states

We study production of entanglement with highly-mixed states. We find that entanglement between highly mixed states can be generated via a direct unitary interaction even when both states have purities arbitrarily close to zero. This indicates that purity of a subsystem is not required for entanglement generation. Our result is in contrast to previous studies where the importance of the subsystem purity was emphasized.Comment: 4 pages, 5 figure

Using macroscopic entanglement to close the detection loophole in Bell inequality

We consider a Bell-like inequality performed using various instances of multi-photon entangled states to demonstrate that losses occurring after the unitary transformations used in the nonlocality test can be counteracted by enhancing the "size" of such entangled states. In turn, this feature can be used to overcome detection inefficiencies affecting the test itself: a slight increase in the size of such states, pushing them towards a more "macroscopic" form of entanglement, significantly improves the state robustness against detection inefficiency, thus easing the closing of the detection loophole. Differently, losses before the unitary transformations cause decoherence effects that cannot be compensated using macroscroscopic entanglement.Comment: 5 pages, 5 figures, to be published in Phys. Rev.

Self-assembled artificial cilia actuator

Department of Mechanical EngineeringSlender hair-like cilia are observed in many living organisms. Cilia carry out important roles, such as locomotion, fluid control, fluid diffusion, and cleaning, owing to their high aspect ratio structure. Inspired by cilia in nature, artificial cilia actuators are being extensively developed. An artificial cilia actuator can generate shape morphing and actuation under external stimuli, such as pneumatic, electric-field, light, thermal, and chemical stimuli as well as a magnetic field. Pneumatic cilia actuators have a large driving force compared to their weight and are easy to manufacture. However, they cannot be miniaturized to a microscale, like cilia in nature, because additional components such as pumps and cables are essential. Electric cilia can be manufactured on a microscale and can actuate dynamicallyhowever, their applications are limited owing to their high voltage requirements. Light, chemical, and thermal stimuli-based cilia actuators can also be miniaturized on a microscale, but they have slow response times and do not easily generate the desired actuation. On the other hand, magnetic actuators can be miniaturized, controlled precisely, are non-invasive, and can be driven immediately. Owing to these advantages, cilia actuators based on magnetic fields have been intensively investigated. Magnetic cilia actuators are mainly constructed using a top-down approach. In this approach, a template mold with a lithographically defined hole array is replicated with a magnetic-particle mixture solution, which enables the reliable fabrication of magnetic cilia with controlled geometry. However, with this technique, synthetic cilia with nanoscopic diameters that are nearly the size of biological cilia are difficult to access owing to the limited pattern resolution of the lithographically prepared template and high viscosity of the composite solution. In addition, the aspect ratio of cilia is limited because the cilia may structurally collapse during a demolding step of the molding process. The self-assembly approach has emerged as a solution to the limitations of the top-down approach. This approach fabricates a desired structure by manipulating a driving force that moves particles, and it has strong potential for constructing a cilia array with a nanoscale size and high aspect ratio structure. The Langmuir???Blodgett conventional self-assembly technique can precisely control particles. However, this technique typically produces close-packed two-dimensional monolayer or three-dimensional lattice structures. Recently, spray-based and DNA-based self-assembly techniques were conducted to construct a vertical structure. However, spray-based self-assembly has random spatial distributions without controllability of the array geometry. DNA-based self-assembly has a complex processtherefore, obtaining a high aspect ratio is challenging. We propose a programmable self-assembly strategy that can direct magnetic particles into a highly ordered responsive artificial cilia actuator. The resulting cilia display several structural features, such as diameters of single-particle resolution, controllable diameters and lengths spanning from nanometers to micrometers, and accurate positioning. The proposed strategy is based on the vapor state, which minimizes intermolecular interaction, and precise magnetic-field control using a Ni island. The self-assembled artificial cilia can maintain their structural integrity through interparticle interactions. Interestingly, the cilia can exhibit a field-responsive actuation motion through ???rolling and sliding??? between assembled particles instead of bending the entire ciliary beam. We demonstrate that oleic acid used to coat the particles acts as a lubricating bearing and enables the rolling/sliding-based actuation of the cilia. We further demonstrate that both magnetic nanocilia and microcilia can dynamically and immediately actuate in response to modulated magnetic fields while providing different stroke ranges and actuation torques.ope

Distilling Self-Supervised Vision Transformers for Weakly-Supervised Few-Shot Classification & Segmentation

We address the task of weakly-supervised few-shot image classification and segmentation, by leveraging a Vision Transformer (ViT) pretrained with self-supervision. Our proposed method takes token representations from the self-supervised ViT and leverages their correlations, via self-attention, to produce classification and segmentation predictions through separate task heads. Our model is able to effectively learn to perform classification and segmentation in the absence of pixel-level labels during training, using only image-level labels. To do this it uses attention maps, created from tokens generated by the self-supervised ViT backbone, as pixel-level pseudo-labels. We also explore a practical setup with ``mixed" supervision, where a small number of training images contains ground-truth pixel-level labels and the remaining images have only image-level labels. For this mixed setup, we propose to improve the pseudo-labels using a pseudo-label enhancer that was trained using the available ground-truth pixel-level labels. Experiments on Pascal-5i and COCO-20i demonstrate significant performance gains in a variety of supervision settings, and in particular when little-to-no pixel-level labels are available.Comment: Accepted at CVPR 202