14,274 research outputs found
Photoproduction of Pentaquark and Chiral Symmetry Restoration in Hot and Dense Medium
The photoproduction rate of pentaquark is calculated in a hot and
dense medium. At high temperature and density, due to the restoration of chiral
symmetry, photoproduction energy threshold is increased. Above the thresold the
production cross section is strongly enhanced.Comment: 5 pages, 3 figure
Adversarial Convolutional Networks with Weak Domain-Transfer for Multi-sequence Cardiac MR Images Segmentation
Analysis and modeling of the ventricles and myocardium are important in the
diagnostic and treatment of heart diseases. Manual delineation of those tissues
in cardiac MR (CMR) scans is laborious and time-consuming. The ambiguity of the
boundaries makes the segmentation task rather challenging. Furthermore, the
annotations on some modalities such as Late Gadolinium Enhancement (LGE) MRI,
are often not available. We propose an end-to-end segmentation framework based
on convolutional neural network (CNN) and adversarial learning. A dilated
residual U-shape network is used as a segmentor to generate the prediction
mask; meanwhile, a CNN is utilized as a discriminator model to judge the
segmentation quality. To leverage the available annotations across modalities
per patient, a new loss function named weak domain-transfer loss is introduced
to the pipeline. The proposed model is evaluated on the public dataset released
by the challenge organizer in MICCAI 2019, which consists of 45 sets of
multi-sequence CMR images. We demonstrate that the proposed adversarial
pipeline outperforms baseline deep-learning methods.Comment: 9 pages, 4 figures, conferenc
Large-Alphabet Encoding Schemes for Floodlight Quantum Key Distribution
Floodlight quantum key distribution (FL-QKD) uses binary phase-shift keying
(BPSK) of multiple optical modes to achieve Gbps secret-key rates (SKRs) at
metropolitan-area distances. We show that FL-QKD's SKR can be doubled by using
32-ary PSK.Comment: 2 pages, 2 figure
Entanglement-Enhanced Lidars for Simultaneous Range and Velocity Measurements
Lidar is a well known optical technology for measuring a target's range and
radial velocity. We describe two lidar systems that use entanglement between
transmitted signals and retained idlers to obtain significant quantum
enhancements in simultaneous measurement of these parameters. The first
entanglement-enhanced lidar circumvents the Arthurs-Kelly uncertainty relation
for simultaneous measurement of range and radial velocity from detection of a
single photon returned from the target. This performance presumes there is no
extraneous (background) light, but is robust to the roundtrip loss incurred by
the signal photons. The second entanglement-enhanced lidar---which requires a
lossless, noiseless environment---realizes Heisenberg-limited accuracies for
both its range and radial-velocity measurements, i.e., their root-mean-square
estimation errors are both proportional to when signal photons are
transmitted. These two lidars derive their entanglement-based enhancements from
use of a unitary transformation that takes a signal-idler photon pair with
frequencies and and converts it to a signal-idler photon
pair whose frequencies are and .
Insight into how this transformation provides its benefits is provided through
an analogy to superdense coding.Comment: 7 pages, 3 figure
Distributed Quantum Sensing Using Continuous-Variable Multipartite Entanglement
Distributed quantum sensing uses quantum correlations between multiple
sensors to enhance the measurement of unknown parameters beyond the limits of
unentangled systems. We describe a sensing scheme that uses continuous-variable
multipartite entanglement to enhance distributed sensing of field-quadrature
displacement. By dividing a squeezed-vacuum state between multiple
homodyne-sensor nodes using a lossless beam-splitter array, we obtain a
root-mean-square (rms) estimation error that scales inversely with the number
of nodes (Heisenberg scaling), whereas the rms error of a distributed sensor
that does not exploit entanglement is inversely proportional to the square root
of number of nodes (standard quantum limit scaling). Our sensor's scaling
advantage is destroyed by loss, but it nevertheless retains an rms-error
advantage in settings in which there is moderate loss. Our distributed sensing
scheme can be used to calibrate continuous-variable quantum key distribution
networks, to perform multiple-sensor cold-atom temperature measurements, and to
do distributed interferometric phase sensing.Comment: 7 pages, 3 figure
Resource theory of non-Gaussian operations
Non-Gaussian states and operations are crucial for various
continuous-variable quantum information processing tasks. To quantitatively
understand non-Gaussianity beyond states, we establish a resource theory for
non-Gaussian operations. In our framework, we consider Gaussian operations as
free operations, and non-Gaussian operations as resources. We define
entanglement-assisted non-Gaussianity generating power and show that it is a
monotone that is non-increasing under the set of free super-operations, i.e.,
concatenation and tensoring with Gaussian channels. For conditional unitary
maps, this monotone can be analytically calculated. As examples, we show that
the non-Gaussianity of ideal photon-number subtraction and photon-number
addition equal the non-Gaussianity of the single-photon Fock state. Based on
our non-Gaussianity monotone, we divide non-Gaussian operations into two
classes: (1) the finite non-Gaussianity class, e.g., photon-number subtraction,
photon-number addition and all Gaussian-dilatable non-Gaussian channels; and
(2) the diverging non-Gaussianity class, e.g., the binary phase-shift channel
and the Kerr nonlinearity. This classification also implies that not all
non-Gaussian channels are exactly Gaussian-dilatable. Our resource theory
enables a quantitative characterization and a first classification of
non-Gaussian operations, paving the way towards the full understanding of
non-Gaussianity.Comment: 15 pages, 4 figure
Voice Service Support in Mobile Ad Hoc Networks
Mobile ad hoc networks are expected to support voice traffic. The requirement
for small delay and jitter of voice traffic poses a significant challenge for
medium access control (MAC) in such networks. User mobility makes it more
complex due to the associated dynamic path attenuation. In this paper, a MAC
scheme for mobile ad hoc networks supporting voice traffic is proposed. With
the aid of a low-power probe prior to DATA transmissions, resource reservation
is achieved in a distributed manner, thus leading to small delay and jitter.
The proposed scheme can automatically adapt to dynamic path attenuation in a
mobile environment. Simulation results demonstrate the effectiveness of the
proposed scheme.Comment: To appear in the Proceedings of the IEEE Global Communications
Conference (GLOBECOM), Washington, DC, November 26 - 30, 200
Low-momentum Pion Enhancement Induced by Chiral Symmetry Restoration
The thermal and nonthermal pion production by sigma decay and its relation
with chiral symmetry restoration in a hot and dense matter are investigated.
The nonthermal decay into pions of sigma mesons which are popularly produced in
chiral symmetric phase leads to a low-momentum pion enhancement as a possible
signature of chiral phase transition at finite temperature and density.Comment: 3 pages, 2 figure
- …