8,280 research outputs found
Distributed quantum sensing enhanced by continuous-variable error correction
A distributed sensing protocol uses a network of local sensing nodes to estimate a global feature of the network, such as a weighted average of locally detectable parameters. In the noiseless case, continuous-variable (CV) multipartite entanglement shared by the nodes can improve the precision of parameter estimation relative to the precision attainable by a network without shared entanglement; for an entangled protocol, the root mean square estimation error scales like 1/M with the number M of sensing nodes, the so-called Heisenberg scaling, while for protocols without entanglement, the error scales like 1√M. However, in the presence of loss and other noise sources, although multipartite entanglement still has some advantages for sensing displacements and phases, the scaling of the precision with M is less favorable. In this paper, we show that using CV error correction codes can enhance the robustness of sensing protocols against imperfections and reinstate Heisenberg scaling up to moderate values of M. Furthermore, while previous distributed sensing protocols could measure only a single quadrature, we construct a protocol in which both quadratures can be sensed simultaneously. Our work demonstrates the value of CV error correction codes in realistic sensing scenarios
Holographic coherent states from random tensor networks
Random tensor networks provide useful models that incorporate various
important features of holographic duality. A tensor network is usually defined
for a fixed graph geometry specified by the connection of tensors. In this
paper, we generalize the random tensor network approach to allow quantum
superposition of different spatial geometries. We set up a framework in which
all possible bulk spatial geometries, characterized by weighted adjacent
matrices of all possible graphs, are mapped to the boundary Hilbert space and
form an overcomplete basis of the boundary. We name such an overcomplete basis
as holographic coherent states. A generic boundary state can be expanded on
this basis, which describes the state as a superposition of different spatial
geometries in the bulk. We discuss how to define distinct classical geometries
and small fluctuations around them. We show that small fluctuations around
classical geometries define "code subspaces" which are mapped to the boundary
Hilbert space isometrically with quantum error correction properties. In
addition, we also show that the overlap between different geometries is
suppressed exponentially as a function of the geometrical difference between
the two geometries. The geometrical difference is measured in an area law
fashion, which is a manifestation of the holographic nature of the states
considered.Comment: 33 pages, 8 figures. An error corrected on page 14. Reference update
Research on Rectal Tumor Identification Method by Convolutional Neural Network Based on Multi-Feature Fusion
Aiming at the obscure features of tumors in rectal CT images and their complexity, this paper proposes a multi-feature fusion-based convolutional neural network rectal tumor recognition method and uses it to model rectal tumors for classification experiments. This method extracts the convolutional features from rectal CT images using Alexnet, VGG16, ResNet, and DenseNet, respectively. At the same time, local features such as histogram of oriented gradient, local binary pattern, and HU moment invariants are extracted from this image. The above local features are fused linearly with the convolutional features. Then we put the new fused features into the fully connected layer for image classification. The experimental results finally reached the accuracy rates of 92.6 %, 93.1 %, 91.7 %, and 91.1 %, respectively. Comparative experiments show that this method improves the accuracy of rectal tumor recognition
Implications of new data in charmless B decays
Based on the latest experimental data of and modes, a
model-independent analytical analysis is presented. The CP-averaged branching
ratio difference in decays with and
is reduced though it remains larger than the prediction from the standard
model(SM) as both measured and are enhanced, which indicates that a
room for new physics becomes smaller. The present data of decay reduce
the ratio from the previous value of to , which is still larger than the theoretical estimations based on
QCD factorization and pQCD. Within SM and flavor SU(3) symmetry, the current
data also diminish the ratio from the previous value to with a large strong phase , while its value remains much larger than the one extracted from
the modes. The direct CP violation is
predicted to be , which is consistent
with the present data. Two kinds of new effects in both strong and weak phases
of the electroweak penguin diagram are considered. It is found that both cases
can reduce the ratio to and lead to roughly the same
predictions for CP violation in .Comment: 13 pages, 4 figure
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