144 research outputs found
A Beam-Steering Reflectarray Antenna with Arbitrary Linear-Polarization Reconfiguration
This work presents a beam-steering reflectarray antenna capable of achieving
arbitrary linear polarization (LP) reconfiguration. It utilizes a dual-circular
polarization (CP) reconfigurable reflectarray, along with an LP feed horn, to
synthesize a LP beam by combining two reflected CP beams in the same direction.
The LP states can be dynamically adjusted by tuning the phase constants of the
array, which correspondingly modify the wave phases. Experimental validation of
the proposed polarization synthesis concept is conducted using a 1616
dual-CP 1-bit reconfigurable reflectarray operating at 16.8 GHz. This
reflectarray generates reconfigurable LP waves with polarization states of
LP(0), LP(45), LP(90) and LP(135). Furthermore,
it demonstrates the capability to perform beam scanning, allowing for versatile
beam manipulation. The application of this polarization-reconfigurable
beam-steering reflectarray is pertinent to beam alignment and polarization
synchronization in various wireless communication scenarios, including
satellite communication and mobile communication
Individual-atom control in array through phase modulation
Performing parallel gate operations while retaining low crosstalk is an
essential step in transforming neutral atom arrays into powerful quantum
computers and simulators. Tightly focusing control beams in small areas for
crosstalk suppression is typically challenging and can lead to imperfect
polarization for certain transitions. We tackle such a problem by introducing a
method to engineer single qubit gates through phase-modulated continuous
driving. Distinct qubits can be individually addressed to high accuracy by
simply tuning the modulation parameters, which significantly suppresses
crosstalk effects. When arranged in a lattice structure, individual control
with optimal crosstalk suppression is achieved. With the assistance of
additional addressing light or multiple modulation frequencies, we develop two
efficient implementations of parallel-gate operations. Our results pave the way
to scaling up atom-array platforms with low-error parallel-gate operations,
without requiring complicated wavefront design or high-power laser beams
Exponentially Enhanced non-Hermitian Cooling
Certain non-Hermitian systems exhibit the skin effect, whereby the
wavefunctions become exponentially localized at one edge of the system. Such
exponential amplification of wavefunction has received significant attention
due to its potential applications in e.g., classical and quantum sensing.
However, the opposite edge of the system, featured by the exponentially
suppressed wavefunctions, remains largely unexplored. Leveraging this
phenomenon, we introduce a non-Hermitian cooling mechanism, which is
fundamentally distinct from traditional refrigeration or laser cooling
techniques. Notably, non-Hermiticity will not amplify thermal excitations, but
rather redistribute them. Hence, thermal excitations can be cooled down at one
edge of the system, and the cooling effect can be exponentially enhanced by the
number of auxiliary modes, albeit with a lower bound that depends on the
dissipative interaction with the environment. Non-Hermitian cooling does not
rely on intricate properties such as exceptional points or non-trivial
topology, and it can apply to a wide range of Bosonic modes such as photons,
phonons, magnons, etc.Comment: 12 pages, 4 figure
Efficient Quantum Transduction Using Anti-Ferromagnetic Topological Insulators
Transduction of quantum information between distinct quantum systems is an
essential step in various applications, including quantum networks and quantum
computing. However, quantum transduction needs to mediate between photons with
vastly different frequencies, making it challenging to design high-performance
transducers, due to multifaceted and sometimes conflicting requirements. In
this work, we first discuss some general principles for quantum transducer
design, and then propose solid-state anti-ferromagnetic topological insulators
to serve as highly effective transducers. First, topological insulators exhibit
band-inversion, which can greatly enhance their optical responses. Coupled with
their robust spin-orbit coupling and high spin density, this property leads to
strong nonlinear interaction in topological insulators, thereby substantially
improving transduction efficiency. Second, the anti-ferromagnetic order can
minimize the detrimental influence on other neighboring quantum systems due to
magnetic interactions. Using as an example, we showcase that
unit transduction fidelity can be achieved with modest experimental
requirements, while the transduction bandwidth can reach the GHz range. The
strong nonlinear interaction in magnetic topological insulators can find
diverse applications, including the generation of entanglement between photons
of distinct frequencies.Comment: 15 pages, 3 figure
A Comprehensive Survey on Orbital Edge Computing: Systems, Applications, and Algorithms
The number of satellites, especially those operating in low-earth orbit
(LEO), is exploding in recent years. Additionally, the use of COTS hardware
into those satellites enables a new paradigm of computing: orbital edge
computing (OEC). OEC entails more technically advanced steps compared to
single-satellite computing. This feature allows for vast design spaces with
multiple parameters, rendering several novel approaches feasible. The mobility
of LEO satellites in the network and limited resources of communication,
computation, and storage make it challenging to design an appropriate
scheduling algorithm for specific tasks in comparison to traditional
ground-based edge computing. This article comprehensively surveys the
significant areas of focus in orbital edge computing, which include protocol
optimization, mobility management, and resource allocation. This article
provides the first comprehensive survey of OEC. Previous survey papers have
only concentrated on ground-based edge computing or the integration of space
and ground technologies. This article presents a review of recent research from
2000 to 2023 on orbital edge computing that covers network design, computation
offloading, resource allocation, performance analysis, and optimization.
Moreover, having discussed several related works, both technological challenges
and future directions are highlighted in the field.Comment: 18 pages, 9 figures and 5 table
DevNet: Self-supervised Monocular Depth Learning via Density Volume Construction
Self-supervised depth learning from monocular images normally relies on the
2D pixel-wise photometric relation between temporally adjacent image frames.
However, they neither fully exploit the 3D point-wise geometric
correspondences, nor effectively tackle the ambiguities in the photometric
warping caused by occlusions or illumination inconsistency. To address these
problems, this work proposes Density Volume Construction Network (DevNet), a
novel self-supervised monocular depth learning framework, that can consider 3D
spatial information, and exploit stronger geometric constraints among adjacent
camera frustums. Instead of directly regressing the pixel value from a single
image, our DevNet divides the camera frustum into multiple parallel planes and
predicts the pointwise occlusion probability density on each plane. The final
depth map is generated by integrating the density along corresponding rays.
During the training process, novel regularization strategies and loss functions
are introduced to mitigate photometric ambiguities and overfitting. Without
obviously enlarging model parameters size or running time, DevNet outperforms
several representative baselines on both the KITTI-2015 outdoor dataset and
NYU-V2 indoor dataset. In particular, the root-mean-square-deviation is reduced
by around 4% with DevNet on both KITTI-2015 and NYU-V2 in the task of depth
estimation. Code is available at https://github.com/gitkaichenzhou/DevNet.Comment: Accepted by European Conference on Computer Vision 2022 (ECCV2022
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