The tapped ions can be cooled close to their motional ground state, which is imperative in implementing quantum computation and quantum simulation. Here we demonstrate the capability of light-mediated chiral couplings between ions, which enables a superior cooling scheme exceeding the single-ion limit of sideband cooling. We present the chiral-coupling-assisted refrigeration in the target ion at the price of heating the others under asymmetric drivings, where its steady-state phonon occupation outperforms the lower bound set by a single ion. We further locate the optimal operation condition of the refrigeration and identify the parameter region where a faster rate of cooling emerges. Under an additional nonguided decay channel, the heating effect in the reciprocal coupling regime becomes suppressed and turns into cooling instead. Our results present a resource of collective chiral couplings which help surpass the bottleneck of cooling procedure in applications of trapped-ion-based quantum computer and simulator.
Rollable photonic devices that can adapt to freeform surfaces with reduced dimensions while maintaining their original functionalities are highly desirable. Among photonic devices, metamaterials with hyperbolic dispersion in momentum space, defined as hyperbolic metamaterial (HMM), possess a large photonic density of states that has been proven to boost light-matter interaction. However, these devices are mainly developed on rigid substrates, restricting their functionalities. Here, we present the attempt to integrate flexible and rollable HMMs consisting of polymer and metal multilayers on paper substrate. Quite interestingly, this design enables to exhibit high photonic density of states and scattering efficiency to enhance stimulated emission and induce pronounced laser action. The flexible and rollable HMM structure remains well its functionalities on freeform surfaces with curvature radius of 1 mm, and can withstand repeated bending without performance degradation. The intensity of laser action is enhanced by 3.5 times as compared to the flat surface. We anticipate that this flexible and rollable HMM structure can serve as a diverse platform for flexible photonic technologies, such as light-emitting devices, wearable optoelectronics, and optical communication.
The objective of this research is to develop a vision-based driver assistance system to enhance the driver's safety in the nighttime. The proposed system performs both lane detection and vehicle recognition. In lane detection, three features including lane markers, brightness, slenderness and proximity are applied to detect the positions of lane markers in the image. On the other hand, vehicle recognition is achieved by using an evident feature which are extracted through three four steps: taillight standing-out process, adaptive thresholding, centroid detection, and taillight pairing algorithm. Besides, an automatic method is also provided to calculate the tilt and the pan of the camera by using the position of vanishing point which is detected in the image by applying Canny edge detection, Hough transform, major straight line extraction and vanishing point estimation. Experimental results for thousands of images are provided to demonstrate the effectiveness of the proposed approach in the nighttime. The lane detection rate is nearly 99%, and the vehicle recognition rate is about 91%. Furthermore, our system can process the image in almost real time.
Cooling the trapped atoms toward their motional ground states is key to applications of quantum simulation and quantum computation. By utilizing nonreciprocal couplings between two atoms, we present an intriguing dark-state cooling scheme in $\Lambda$-type three-level structure, which is shown superior than the conventional electromagnetically-induced-transparency cooling in a single atom. The effective nonreciprocal couplings can be facilitated either by an atom-waveguide interface or a free-space photonic quantum link. By tailoring system parameters allowed in dark-state cooling, we identify the parameter regions of better cooling performance with an enhanced cooling rate. We further demonstrate a mapping to the dark-state sideband cooling under asymmetric laser driving fields, which shows a distinct heat transfer and promises an outperforming dark-state sideband cooling assisted by collective spin-exchange interactions.
Trapped ions can be cooled close to their motional ground state, which is imperative in implementing quantum computation and quantum simulation. Here we theoretically investigate the capability of light-mediated chiral couplings between ions, which enables a superior cooling scheme exceeding the single-ion limit of sideband cooling. Under asymmetric drivings, the target ion manifests the chiral-coupling-assisted refrigeration at the price of heating the others, where its steady-state phonon occupation outperforms the lower bound set by a single ion. We further explore the optimal operation conditions of the refrigeration, where a faster rate of cooling can still be sustained. Under an additional nonguided decay channel, a broader parameter regime emerges to support the superior cooling and carries over into the reciprocal coupling, suppressing the heating effect instead. Our results present a tunable resource of collective chiral couplings which can help surpass the bottleneck of cooling procedure and open up new possibilities in applications of trapped-ion-based quantum computer and simulator.
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