4,162 research outputs found
IPDAE: Improved Patch-Based Deep Autoencoder for Lossy Point Cloud Geometry Compression
Point cloud is a crucial representation of 3D contents, which has been widely
used in many areas such as virtual reality, mixed reality, autonomous driving,
etc. With the boost of the number of points in the data, how to efficiently
compress point cloud becomes a challenging problem. In this paper, we propose a
set of significant improvements to patch-based point cloud compression, i.e., a
learnable context model for entropy coding, octree coding for sampling centroid
points, and an integrated compression and training process. In addition, we
propose an adversarial network to improve the uniformity of points during
reconstruction. Our experiments show that the improved patch-based autoencoder
outperforms the state-of-the-art in terms of rate-distortion performance, on
both sparse and large-scale point clouds. More importantly, our method can
maintain a short compression time while ensuring the reconstruction quality.Comment: 12 page
Channel Estimation for Reconfigurable Intelligent Surface-Aided Multiuser Communication Systems Exploiting Statistical CSI of Correlated RIS-User Channels
Reconfigurable intelligent surface (RIS) is a promising candidate technology
for the upcoming Sixth Generation (6G) communication system for its ability to
manipulate the wireless communication environment by controlling the
coefficients of reflection elements (REs). However, since the RIS usually
consists of a large number of passive REs, the pilot overhead for channel
estimation in the RIS-aided system is prohibitively high. In this paper, the
channel estimation problem for a RIS-aided multi-user
multiple-input-single-output (MISO) communication system with clustered users
is investigated. First, to describe the correlated feature for RIS-user
channels, a beam domain channel model is developed for RIS-user channels. Then,
a pilot reuse strategy is put forward to reduce the pilot overhead and
decompose the channel estimation problem into several subproblems. Finally, by
leveraging the correlated nature of RIS-user channels, an eigenspace projection
(EP) algorithm is proposed to solve each subproblem respectively. Simulation
results show that the proposed EP channel estimation scheme can achieve
accurate channel estimation with lower pilot overhead than existing schemes.Comment: 10 pages, 11 figure
Statistical CSI Based Beamforming for Reconfigurable Intelligent Surface Aided MISO Systems with Channel Correlation
Reconfigurable intelligent surface (RIS) is a promising candidate technology
of the upcoming Sixth Generation (6G) communication system for its ability to
provide unprecedented spectral and energy efficiency increment through passive
beamforming. However, it is challenging to obtain instantaneous channel state
information (I-CSI) for RIS, which obliges us to use statistical channel state
information (S-CSI) to achieve passive beamforming. In this paper, RIS-aided
multiple-input single-output (MISO) multi-user downlink communication system
with correlated channels is investigated. Then, we formulate the problem of
joint beamforming design at the AP and RIS to maximize the sum ergodic spectral
efficiency (ESE) of all users to improve the network capacity. Since it is too
hard to compute sum ESE, an ESE approximation is adopted to reformulate the
problem into a more tractable form. Then, we present two joint beamforming
algorithms, namely the singular value decomposition-gradient descent (SVD-GD)
algorithm and the fractional programming-gradient descent (FP-GD) algorithm.
Simulation results show the effectiveness of our proposed algorithms and
validate that 2-bits quantizer is enough for RIS phase shifts implementation.Comment: 10 pages, 9 figures
Experimental preparation and verification of quantum money
A quantum money scheme enables a trusted bank to provide untrusted users with
verifiable quantum banknotes that cannot be forged. In this work, we report an
experimental demonstration of the preparation and verification of unforgeable
quantum banknotes. We employ a security analysis that takes experimental
imperfections fully into account. We measure a total of states
in one verification round, limiting the forging probability to based
on the security analysis. Our results demonstrate the feasibility of preparing
and verifying quantum banknotes using currently available experimental
techniques.Comment: 12 pages, 4 figure
Improvements to enhance robustness of third-order scale-independent WENO-Z schemes
Although there are many improvements to WENO3-Z that target the achievement
of optimal order in the occurrence of the first-order critical point (CP1),
they mainly address resolution performance, while the robustness of schemes is
of less concern and lacks understanding accordingly. In light of our analysis
considering the occurrence of critical points within grid intervals, we
theoretically prove that it is impossible for a scale-independent scheme that
has the stencil of WENO3-Z to fulfill the above order achievement, and current
scale-dependent improvements barely fulfill the job when CP1 occurs at the
middle of the grid cell. In order to achieve scale-independent improvements, we
devise new smoothness indicators that increase the error order from 2 to 4 when
CP1 occurs and perform more stably. Meanwhile, we construct a new global
smoothness indicator that increases the error order from 4 to 5 similarly,
through which new nonlinear weights with regard to WENO3-Z are derived and new
scale-independents improvements, namely WENO-ZES2 and -ZES3, are acquired.
Through 1D scalar and Euler tests, as well as 2D computations, in comparison
with typical scale-dependent improvement, the following performances of the
proposed schemes are demonstrated: The schemes can achieve third-order accuracy
at CP1 no matter its location in the stencil, indicate high resolution in
resolving flow subtleties, and manifest strong robustness in hypersonic
simulations (e.g., the accomplishment of computations on hypersonic
half-cylinder flow with Mach numbers reaching 16 and 19, respectively, as well
as essentially non-oscillatory solutions of inviscid sharp double cone flow at
M=9.59), which contrasts the comparative WENO3-Z improvement
10-Ethyl-3-(5-methyl-1,3,4-oxadiazol-2-yl)-10H-phenothiazine
In the title compound, C17H15N3OS, the phenothiazine ring system is slightly bent, with a dihedral angle of 13.68 (7)° between the benzene rings. The dihedral angle between the oxadiazole ring and the adjacent benzene ring is 7.72 (7)°. In the crystal, a π–π interaction with a centroid–centroid distance of 3.752 (2) Å is observed between the benzene rings of neighbouring molecules
Observation of quantum fingerprinting beating the classical limit
Quantum communication has historically been at the forefront of advancements,
from fundamental tests of quantum physics to utilizing the quantum-mechanical
properties of physical systems for practical applications. In the field of
communication complexity, quantum communication allows the advantage of an
exponential reduction in the information transmitted over classical
communication to accomplish distributed computational tasks. However, to date,
demonstrating this advantage in a practical setting continues to be a central
challenge. Here, we report an experimental demonstration of a quantum
fingerprinting protocol that for the first time surpasses the ultimate
classical limit to transmitted information. Ultra-low noise superconducting
single-photon detectors and a stable fibre-based Sagnac interferometer are used
to implement a quantum fingerprinting system that is capable of transmitting
less information than the classical proven lower bound over 20 km standard
telecom fibre for input sizes of up to two Gbits. The results pave the way for
experimentally exploring the advanced features of quantum communication and
open a new window of opportunity for research in communication complexity and
testing the foundations of physics.Comment: 19 pages, 4 figure
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