149 research outputs found
Monodromy analysis of the computational power of the Ising topological quantum computer
We show that all quantum gates which could be implemented by braiding of
Ising anyons in the Ising topological quantum computer preserve the n-qubit
Pauli group. Analyzing the structure of the Pauli group's centralizer, also
known as the Clifford group, for n\geq 3 qubits, we prove that the image of the
braid group is a non-trivial subgroup of the Clifford group and therefore not
all Clifford gates could be implemented by braiding. We show explicitly the
Clifford gates which cannot be realized by braiding estimating in this way the
ultimate computational power of the Ising topological quantum computer.Comment: 10 pages, 2 figures and 1 table; v2: one more reference added and
some typos corrected; Talk given at the VIII International Workshop "Lie
Theory and its Applications in Physics", 15-21 June 2009, Varna, Bulgari
The Multi-Agent Programming Contest: A r\'esum\'e
The Multi-Agent Programming Contest, MAPC, is an annual event organized since
2005 out of Clausthal University of Technology. Its aim is to investigate the
potential of using decentralized, autonomously acting intelligent agents, by
providing a complex scenario to be solved in a competitive environment. For
this we need suitable benchmarks where agent-based systems can shine. We
present previous editions of the contest and also its current scenario and
results from its use in the 2019 MAPC with a special focus on its suitability.
We conclude with lessons learned over the years.Comment: Submitted to the proceedings of the Multi-Agent Programming Contest
2019, to appear in Springer Lect. Notes Computer Challenges Series
https://www.springer.com/series/1652
Recurrence for discrete time unitary evolutions
We consider quantum dynamical systems specified by a unitary operator U and
an initial state vector \phi. In each step the unitary is followed by a
projective measurement checking whether the system has returned to the initial
state. We call the system recurrent if this eventually happens with probability
one. We show that recurrence is equivalent to the absence of an absolutely
continuous part from the spectral measure of U with respect to \phi. We also
show that in the recurrent case the expected first return time is an integer or
infinite, for which we give a topological interpretation. A key role in our
theory is played by the first arrival amplitudes, which turn out to be the
(complex conjugated) Taylor coefficients of the Schur function of the spectral
measure. On the one hand, this provides a direct dynamical interpretation of
these coefficients; on the other hand it links our definition of first return
times to a large body of mathematical literature.Comment: 27 pages, 5 figures, typos correcte
Green function approach for scattering quantum walks
In this work a Green function approach for scattering quantum walks is
developed. The exact formula has the form of a sum over paths and always can be
cast into a closed analytic expression for arbitrary topologies and position
dependent quantum amplitudes. By introducing the step and path operators, it is
shown how to extract any information about the system from the Green function.
The method relevant features are demonstrated by discussing in details an
example, a general diamond-shaped graph.Comment: 13 pages, 6 figures, this article was selected by APS for Virtual
Journal of Quantum Information, Vol 11, Iss 11 (2011
Implementation of Clifford gates in the Ising-anyon topological quantum computer
We give a general proof for the existence and realizability of Clifford gates
in the Ising topological quantum computer. We show that all quantum gates that
can be implemented by braiding of Ising anyons are Clifford gates. We find that
the braiding gates for two qubits exhaust the entire two-qubit Clifford group.
Analyzing the structure of the Clifford group for n \geq 3 qubits we prove that
the the image of the braid group is a non-trivial subgroup of the Clifford
group so that not all Clifford gates could be implemented by braiding in the
Ising topological quantum computation scheme. We also point out which Clifford
gates cannot in general be realized by braiding.Comment: 17 pages, 10 figures, RevTe
Localization of the Grover walks on spidernets and free Meixner laws
A spidernet is a graph obtained by adding large cycles to an almost regular
tree and considered as an example having intermediate properties of lattices
and trees in the study of discrete-time quantum walks on graphs. We introduce
the Grover walk on a spidernet and its one-dimensional reduction. We derive an
integral representation of the -step transition amplitude in terms of the
free Meixner law which appears as the spectral distribution. As an application
we determine the class of spidernets which exhibit localization. Our method is
based on quantum probabilistic spectral analysis of graphs.Comment: 32 page
Disordered Quantum Walks in one lattice dimension
We study a spin-1/2-particle moving on a one dimensional lattice subject to
disorder induced by a random, space-dependent quantum coin. The discrete time
evolution is given by a family of random unitary quantum walk operators, where
the shift operation is assumed to be deterministic. Each coin is an independent
identically distributed random variable with values in the group of two
dimensional unitary matrices. We derive sufficient conditions on the
probability distribution of the coins such that the system exhibits dynamical
localization. Put differently, the tunneling probability between two lattice
sites decays rapidly for almost all choices of random coins and after arbitrary
many time steps with increasing distance. Our findings imply that this effect
takes place if the coin is chosen at random from the Haar measure, or some
measure continuous with respect to it, but also for a class of discrete
probability measures which support consists of two coins, one of them being the
Hadamard coin.Comment: minor change
Origin and characterization of alpha smooth muscle actin-positive cells during murine lung development
© 2017 The Authors Stem Cells published by Wiley Periodicals, Inc. on behalf of AlphaMed PressACTA2 expression identifies pulmonary airway and vascular smooth muscle cells (SMCs) as well as alveolar myofibroblasts (MYF). Mesenchymal progenitors expressing fibroblast growth factor 10 (Fgf10), Wilms tumor 1 (Wt1), or glioma-associated oncogene 1 (Gli1) contribute to SMC formation from early stages of lung development. However, their respective contribution and specificity to the SMC and/or alveolar MYF lineages remain controversial. In addition, the contribution of mesenchymal cells undergoing active WNT signaling remains unknown. Using Fgf10CreERT2, Wt1CreERT2, Gli1CreERT2, and Axin2CreERT2 inducible driver lines in combination with a tdTomatoflox reporter line, the respective differentiation of each pool of labeled progenitor cells along the SMC and alveolar MYF lineages was quantified. The results revealed that while FGF10+ and WT1+ cells show a minor contribution to the SMC lineage, GLI1+ and AXIN2+ cells significantly contribute to both the SMC and alveolar MYF lineages, but with limited specificity. Lineage tracing using the Acta2-CreERT2 transgenic line showed that ACTA2+ cells labeled at embryonic day (E)11.5 do not expand significantly to give rise to new SMCs at E18.5. However, ACTA2+ cells labeled at E15.5 give rise to the majority (85%–97%) of the SMCs in the lung at E18.5 as well as alveolar MYF progenitors in the lung parenchyma. Fluorescence-activated cell sorting-based isolation of different subpopulations of ACTA2+ lineage-traced cells followed by gene arrays, identified transcriptomic signatures for alveolar MYF progenitors versus airway and vascular SMCs at E18.5. Our results establish a new transcriptional landscape for further experiments addressing the function of signaling pathways in the formation of different subpopulations of ACTA2+ cells. Stem Cells 2017;35:1566–1578
Quantum walks: a comprehensive review
Quantum walks, the quantum mechanical counterpart of classical random walks,
is an advanced tool for building quantum algorithms that has been recently
shown to constitute a universal model of quantum computation. Quantum walks is
now a solid field of research of quantum computation full of exciting open
problems for physicists, computer scientists, mathematicians and engineers.
In this paper we review theoretical advances on the foundations of both
discrete- and continuous-time quantum walks, together with the role that
randomness plays in quantum walks, the connections between the mathematical
models of coined discrete quantum walks and continuous quantum walks, the
quantumness of quantum walks, a summary of papers published on discrete quantum
walks and entanglement as well as a succinct review of experimental proposals
and realizations of discrete-time quantum walks. Furthermore, we have reviewed
several algorithms based on both discrete- and continuous-time quantum walks as
well as a most important result: the computational universality of both
continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing
Journa
Targeting miR-34a/Pdgfra interactions partially corrects alveologenesis in experimental bronchopulmonary dysplasia
Bronchopulmonary dysplasia (BPD) is a common complication of preterm birth characterized by arrested lung alveolarization, which generates lungs that are incompetent for effective gas exchange. We report here deregulated expression of miR-34a in a hyperoxia-based mouse model of BPD, where miR-34a expression was markedly increased in platelet-derived growth factor receptor (PDGFR)α-expressing myofibroblasts, a cell type critical for proper lung alveolarization. Global deletion of miR-34a; and inducible, conditional deletion of miR-34a in PDGFRα+ cells afforded partial protection to the developing lung against hyperoxia-induced perturbations to lung architecture. Pdgfra mRNA was identified as the relevant miR-34a target, and using a target site blocker in vivo, the miR-34a/Pdgfra interaction was validated as a causal actor in arrested lung development. An antimiR directed against miR-34a partially restored PDGFRα+ myofibroblast abundance and improved lung alveolarization in newborn mice in an experimental BPD model. We present here the first identification of a pathology-relevant microRNA/mRNA target interaction in aberrant lung alveolarization and highlight the translational potential of targeting the miR-34a/Pdgfra interaction to manage arrested lung development associated with preterm birth
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