4,730 research outputs found
Generation of two-giant-atom entanglement in waveguide-QED systems
We study the generation of quantum entanglement between two giant atoms
coupled to a one-dimensional waveguide. Since each giant atom interacts with
the waveguide at two separate coupling points, there exist three different
coupling configurations in the two-atom waveguide system: the separated,
braided, and nested couplings. Within the Wigner-Weisskopf framework for single
coupling points, the quantum master equations governing the evolution of the
two giant atoms are obtained. For each coupling configuration, the entanglement
dynamics of the two giant atoms is studied, including the cases of two
different atomic initial states: single- and double-excitation states. It is
shown that the generated entanglement depends on the coupling configuration,
phase shift, and atomic initial state. For the single-excitation initial state,
there exists steady-state entanglement for these three couplings due to the
appearance of the dark state. For the double-excitation initial state, an
entanglement sudden birth is observed via adjusting the phase shift. In
particular, the maximal entanglement for the nested coupling is about one order
of magnitude larger than those of separate and braided couplings. In addition,
the influence of the atomic frequency detuning on the entanglement generation
is studied. This work can be utilized for the generation and control of atomic
entanglement in quantum networks based on giant-atom waveguide-QED systems,
which have wide potential applications in quantum information processing.Comment: 13 pages, 8 figures, to appear in Physical Review A. arXiv admin
note: substantial text overlap with arXiv:2303.1474
Sky-GVINS: a Sky-segmentation Aided GNSS-Visual-Inertial System for Robust Navigation in Urban Canyons
Integrating Global Navigation Satellite Systems (GNSS) in Simultaneous
Localization and Mapping (SLAM) systems draws increasing attention to a global
and continuous localization solution. Nonetheless, in dense urban environments,
GNSS-based SLAM systems will suffer from the Non-Line-Of-Sight (NLOS)
measurements, which might lead to a sharp deterioration in localization
results. In this paper, we propose to detect the sky area from the up-looking
camera to improve GNSS measurement reliability for more accurate position
estimation. We present Sky-GVINS: a sky-aware GNSS-Visual-Inertial system based
on a recent work called GVINS. Specifically, we adopt a global threshold method
to segment the sky regions and non-sky regions in the fish-eye sky-pointing
image and then project satellites to the image using the geometric relationship
between satellites and the camera. After that, we reject satellites in non-sky
regions to eliminate NLOS signals. We investigated various segmentation
algorithms for sky detection and found that the Otsu algorithm reported the
highest classification rate and computational efficiency, despite the
algorithm's simplicity and ease of implementation. To evaluate the
effectiveness of Sky-GVINS, we built a ground robot and conducted extensive
real-world experiments on campus. Experimental results show that our method
improves localization accuracy in both open areas and dense urban environments
compared to the baseline method. Finally, we also conduct a detailed analysis
and point out possible further directions for future research. For detailed
information, visit our project website at
https://github.com/SJTU-ViSYS/Sky-GVINS
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