824 research outputs found
Complex-valued Retrievals From Noisy Images Using Diffusion Models
In diverse microscopy modalities, sensors measure only real-valued
intensities. Additionally, the sensor readouts are affected by
Poissonian-distributed photon noise. Traditional restoration algorithms
typically aim to minimize the mean squared error (MSE) between the original and
recovered images. This often leads to blurry outcomes with poor perceptual
quality. Recently, deep diffusion models (DDMs) have proven to be highly
capable of sampling images from the a-posteriori probability of the sought
variables, resulting in visually pleasing high-quality images. These models
have mostly been suggested for real-valued images suffering from Gaussian
noise. In this study, we generalize annealed Langevin Dynamics, a type of DDM,
to tackle the fundamental challenges in optical imaging of complex-valued
objects (and real images) affected by Poisson noise. We apply our algorithm to
various optical scenarios, such as Fourier Ptychography, Phase Retrieval, and
Poisson denoising. Our algorithm is evaluated on simulations and biological
empirical data.Comment: 11 pages, 7figure
Row, Row, Row Your Boat: How to Not Find Weak Keys in Pilsung
OnlinePublThe Pilsung cipher is part of the North Korean Red Star operating system, which was leaked to the West in 2014. Initial analysis by Kryptos Logic reported a possibility of a class of weak keys due to the use of pseudo-random diffusion. Following this lead, we analyzed the cipher and identified a small class of such weak keys. We developed techniques for searching for a key that belongs to the class. After spending thousands of CPU hours, we found a supposedly weak key for a slightly weaker version of Pilsung, but the key did not behave as we expected. On further investigation we found out a crucial misunderstanding in a critical part of the cipher and that no such class of weak keys exists in Pilsung. Thus, this paper makes two main contributions to the art of cryptanalysis. First, it identifies and shows how to investigate a potential weakness in randomizing diffusion, which although does not exist in Pilsung, may affect future designs. Second, it highlights the need for early verification of results in order to identify errors before expending significant resources.Chitchanok Chuengsatiansup, Eyal Ronen, Gregory G. Rose, and Yuval Yaro
Introduction to topological superconductivity and Majorana fermions
This short review article provides a pedagogical introduction to the rapidly
growing research field of Majorana fermions in topological superconductors. We
first discuss in some details the simplest "toy model" in which Majoranas
appear, namely a one-dimensional tight-binding representation of a p-wave
superconductor, introduced more than ten years ago by Kitaev. We then give a
general introduction to the remarkable properties of Majorana fermions in
condensed matter systems, such as their intrinsically non-local nature and
exotic exchange statistics, and explain why these quasiparticles are suspected
to be especially well suited for low-decoherence quantum information
processing. We also discuss the experimentally promising (and perhaps already
successfully realized) possibility of creating topological superconductors
using semiconductors with strong spin-orbit coupling, proximity-coupled to
standard s-wave superconductors and exposed to a magnetic field. The goal is to
provide an introduction to the subject for experimentalists or theorists who
are new to the field, focusing on the aspects which are most important for
understanding the basic physics. The text should be accessible for readers with
a basic understanding of quantum mechanics and second quantization, and does
not require knowledge of quantum field theory or topological states of matter.Comment: 21 pages, 5 figure
Tailored carrier/bacteria technology for rehabilitation of areas with pesticide-containing pollution – AQUAREHAB WP2
Postprint (published version
Coarse-Graining and Self-Dissimilarity of Complex Networks
Can complex engineered and biological networks be coarse-grained into smaller
and more understandable versions in which each node represents an entire
pattern in the original network? To address this, we define coarse-graining
units (CGU) as connectivity patterns which can serve as the nodes of a
coarse-grained network, and present algorithms to detect them. We use this
approach to systematically reverse-engineer electronic circuits, forming
understandable high-level maps from incomprehensible transistor wiring: first,
a coarse-grained version in which each node is a gate made of several
transistors is established. Then, the coarse-grained network is itself
coarse-grained, resulting in a high-level blueprint in which each node is a
circuit-module made of multiple gates. We apply our approach also to a
mammalian protein-signaling network, to find a simplified coarse-grained
network with three main signaling channels that correspond to cross-interacting
MAP-kinase cascades. We find that both biological and electronic networks are
'self-dissimilar', with different network motifs found at each level. The
present approach can be used to simplify a wide variety of directed and
nondirected, natural and designed networks.Comment: 11 pages, 11 figure
Strong dipolar effects in a quantum ferrofluid
We report on the realization of a Chromium Bose-Einstein condensate (BEC)
with strong dipolar interaction. By using a Feshbach resonance, we reduce the
usual isotropic contact interaction, such that the anisotropic magnetic
dipole-dipole interaction between 52Cr atoms becomes comparable in strength.
This induces a change of the aspect ratio of the cloud, and, for strong dipolar
interaction, the inversion of ellipticity during expansion - the usual "smoking
gun" evidence for BEC - can even be suppressed. These effects are accounted for
by taking into account the dipolar interaction in the superfluid hydrodynamic
equations governing the dynamics of the gas, in the same way as classical
ferrofluids can be described by including dipolar terms in the classical
hydrodynamic equations. Our results are a first step in the exploration of the
unique properties of quantum ferrofluids.Comment: Final, published versio
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