1,509 research outputs found
A Dual Sparse Decomposition Method for Image Denoising
This article addresses the image denoising problem in the situations of
strong noise. We propose a dual sparse decomposition method. This method makes
a sub-dictionary decomposition on the over-complete dictionary in the sparse
decomposition. The sub-dictionary decomposition makes use of a novel criterion
based on the occurrence frequency of atoms of the over-complete dictionary over
the data set. The experimental results demonstrate that the
dual-sparse-decomposition method surpasses state-of-art denoising performance
in terms of both peak-signal-to-noise ratio and
structural-similarity-index-metric, and also at subjective visual quality.Comment: 6 pages, 5 figure
Security of modified Ping-Pong protocol in noisy and lossy channel
The "Ping-Pong" (PP) protocol is a two-way quantum key protocol based on
entanglement. In this protocol, Bob prepares one maximally entangled pair of
qubits, and sends one qubit to Alice. Then, Alice performs some necessary
operations on this qubit and sends it back to Bob. Although this protocol was
proposed in 2002, its security in the noisy and lossy channel has not been
proven. In this report, we add a simple and experimentally feasible
modification to the original PP protocol, and prove the security of this
modified PP protocol against collective attacks when the noisy and lossy
channel is taken into account. Simulation results show that our protocol is
practical.Comment: 7 pages, 2 figures, published in scientific report
More randomness from a prepare-and-measure scenario with independent devices
How to generate genuine quantum randomness from untrusted devices is an
important problem in quantum information processing. Inspired by previous work
on a self-testing quantum random number generator [T. Lunghi et al., Phys. Rev.
Lett. 114, 150501 (2015)], we present a method to generate quantum randomness
from a prepare-and-measure scenario with independent devices. In existing
protocols, the quantum randomness depends only on a witness value (e.g.,
Clauser-Horne-Shimony-Holt value), which is calculated with the observed
probabilities. Differently, here all the observed probabilities are directly
used to calculate the min-entropy in our method. Through numerical simulation,
we find that the min-entropy of our proposed scheme is higher than that in the
previous work when a typical untrusted Bennett-Brassard 1984 (BB84) setup is
used. Consequently, thanks to the proposed method, more genuine quantum random
numbers may be obtained than before.Comment: 8 pages, 3 figure
The collision consistency of lattice-BGK model for simulating rarified gas flows in microchannels
The collision consistency between the BGK collision model equation and
lattice-BGK (LBGK) model is proposed by researching the physical significance
of the relaxation factor tau in LBGK model. For microscalar flow in which the
continuum hypothesis is not still satisfied, the collision consistency tau=1.0
should be ensured when using the LBGK model for simulating microflows. The
results of simulating microchannel Poiseuille flow with constant pressure
gradient under collision consistency by using LBGK model are well consistent
with the analytical solutions, and the accuracy of these results is three or
four orders of magnitude higher than those that don't satisfy the collision
consistency.Comment: Preliminary versio
Security of "Counterfactual Quantum Cryptography"
Recently, a "counterfactual" quantum key distribution scheme was proposed by
Tae-Gon Noh [1]. In this scheme, two legitimate distant peers may share secret
keys even when the information carriers are not traveled in the quantum
channel. We find that this protocol is equivalent to an entanglement
distillation protocol (EDP). According to this equivalence, a strict security
proof and the asymptotic key bit rate are both obtained when perfect single
photon source is applied and Trojan-horse attack can be detected. We also find
that the security of this scheme is deeply related with not only the bit error
rate but also the yields of photons. And our security proof may shed light on
security of other two-way protocols.Comment: 5 pages, 1 figur
Quantum key distribution based on quantum dimension and independent devices
In this paper, we propose a quantum key distribution (QKD) protocol based on
only a two-dimensional Hilbert space encoding a quantum system and independent
devices between the equipment for state preparation and measurement. Our
protocol is inspired by the fully device-independent quantum key distribution
(FDI-QKD) protocol and the measurement-device-independent quantum key
distribution (MDI-QKD) protocol. Our protocol only requires the state to be
prepared in the two dimensional Hilbert space, which weakens the state
preparation assumption in the original MDI-QKD protocol. More interestingly,
our protocol can overcome the detection loophole problem in the FDI-QKD
protocol, which greatly limits the application of FDI-QKD. Hence our protocol
can be implemented with practical optical components
A patient-specific scatter artifacts correction method
This paper provides a fast and patient-specific scatter artifact correction
method for cone-beam computed tomography (CBCT) used in image-guided
interventional procedures. Due to increased irradiated volume of interest in
CBCT imaging, scatter radiation has increased dramatically compared to 2D
imaging, leading to a degradation of image quality. In this study, we propose a
scatter artifact correction strategy using an analytical convolution-based
model whose free parameters are estimated using a rough estimation of scatter
profiles from the acquired cone-beam projections. It was evaluated using Monte
Carlo simulations with both monochromatic and polychromatic X-ray sources. The
results demonstrated that the proposed method significantly reduced the
scatter-induced shading artifacts and recovered CT numbers
Device and semi-device independent random numbers based on non-inequality paradox
In this work, we propose device independent true random numbers generation
protocols based on non-inequality paradoxes such as Hardy's and Cabello's
non-locality argument. The efficiency of generating randomness in our protocols
are far better than any other proposed protocols certified by CHSH inequality
or other non-locality test involving inequalities. Thus, highlighting
non-inequality paradox as an important resource for device independent quantum
information processing in particular generating true randomness. As a
byproduct, we find that the non-local bound of the Cabello's argument with
arbitrary dimension is the same as the one achieved in the qubits system. More
interestingly, we propose a new dimension witness paradox based on the
Cabello's argument, which can be used for constructing semi-device-independent
true random numbers generation protocol
Detection efficiency and noise in semi-device independent randomness extraction protocol
In this paper, we analyze several critical issues in semi-device independent
quantum information processing protocol. In practical experimental realization
randomness generation in that scenario is possible only if the efficiency of
the detectors used is above a certain threshold. Our analysis shows that the
critical detection efficiency is 0.7071 in the symmetric setup, while in the
asymmetric setup if one of the bases has perfect critical detection efficiency
then the other one can be arbitrarily close to 0. We also analyze the
semi-device independent random number generation efficiency based on different
averages of guessing probability. To generate more randomness, the proper
averaging method should be applied. Its choice depends on the value of a
certain dimension witness. More importantly, the general analytical
relationship between the maximal average guessing probability and dimension
witness is given
Principal Basis Analysis in Sparse Representation
This article introduces a new signal analysis method, which can be
interpreted as a principal component analysis in sparse decomposition of the
signal. The method, called principal basis analysis, is based on a novel
criterion: reproducibility of component which is an intrinsic characteristic of
regularity in natural signals. We show how to measure reproducibility. Then we
present the principal basis analysis method, which chooses, in a sparse
representation of the signal, the components optimizing the reproducibility
degree to build the so-called principal basis. With this principal basis, we
show that the underlying signal pattern could be effectively extracted from
corrupted data. As illustration, we apply the principal basis analysis to image
denoising corrupted by Gaussian and non-Gaussian noises, showing better
performances than some reference methods at suppressing strong noise and at
preserving signal details.Comment: The text propose a Principal Basis Analysis in Sparse Representation
and apply the principal basis analysis to image denoising corrupted by
Gaussian and non-Gaussian noises, showing better performances than some
reference methods at suppressing strong noise and at preserving signal
details;including 8 pages, 4 figures prepared using pdf according to the
instructions to Author
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