2,888 research outputs found
Gossip Algorithms for Distributed Signal Processing
Gossip algorithms are attractive for in-network processing in sensor networks
because they do not require any specialized routing, there is no bottleneck or
single point of failure, and they are robust to unreliable wireless network
conditions. Recently, there has been a surge of activity in the computer
science, control, signal processing, and information theory communities,
developing faster and more robust gossip algorithms and deriving theoretical
performance guarantees. This article presents an overview of recent work in the
area. We describe convergence rate results, which are related to the number of
transmitted messages and thus the amount of energy consumed in the network for
gossiping. We discuss issues related to gossiping over wireless links,
including the effects of quantization and noise, and we illustrate the use of
gossip algorithms for canonical signal processing tasks including distributed
estimation, source localization, and compression.Comment: Submitted to Proceedings of the IEEE, 29 page
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Resilient Pathways to Atomic Attachment of Quantum Dot Dimers and Artificial Solids from Faceted CdSe Quantum Dot Building Blocks.
The goal of this work is to identify favored pathways for preparation of defect-resilient attached wurtzite CdX (X = S, Se, Te) nanocrystals. We seek guidelines for oriented attachment of faceted nanocrystals that are most likely to yield pairs of nanocrystals with either few or no electronic defects or electronic defects that are in and of themselves desirable and stable. Using a combination of in situ high-resolution transmission electron microscopy (HRTEM) and electronic structure calculations, we evaluate the relative merits of atomic attachment of wurtzite CdSe nanocrystals on the {11̅00} or {112̅0} family of facets. Pairwise attachment on either facet can lead to perfect interfaces, provided the nanocrystal facets are perfectly flat and the angles between the nanocrystals can adjust during the assembly. Considering defective attachment, we observe for {11̅00} facet attachment that only one type of edge dislocation forms, creating deep hole traps. For {112̅0} facet attachment, we observe that four distinct types of extended defects form, some of which lead to deep hole traps whereas others only to shallow hole traps. HRTEM movies of the dislocation dynamics show that dislocations at {11̅00} interfaces can be removed, albeit slowly. Whereas only some extended defects at {112̅0} interfaces could be removed, others were trapped at the interface. Based on these insights, we identify the most resilient pathways to atomic attachment of pairs of wurtzite CdX nanocrystals and consider how these insights can translate to the creation of electronically useful materials from quantum dots with other crystal structures
Anyon models in quantum codes and topological superconductors
Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física Teórica, leída el 27-11-2020En esta tesis estudiamos dos temas relacionados con la información cuántica y la topología: los superconductores topológicos y la corrección cuántica topológica de errores. Los superconductores topológicos han sido ampliamente estudiados, hecho parcialmente motivado por la búsqueda de fermiones de Majorana en sistemas de materia condensada. Estas cuasipartículas son anyones no abelianos y se pueden utilizar para el procesamiento de información cuántica. Recientemente se han presentado varias propuestas y experimentos en los que se obtienen superconductores topológicos mediante la construcción de heteroestructuras. Dichas heteroestructuras generalmente consisten en un superconductor de onda s acoplado a un semiconductor. En la publicación [P1] exploramos la posibilidad de diseñar un superconductor topológico utilizando un superconductor padre de onda d acoplado a un gas de electrones bidimensional con interacción de espín-órbita y un campo Zeeman. Hallamos una expresión analítica de los estados de Majorana y comparamos estos resultados con los obtenidos cuando se usa un superconductor de ondas convencional.In this thesis we study two main topics related to the interplay between quantum information and topology: topological superconductors and topological quantum error correction. Topological superconductors have been extensively studied, partly motivated by the search of a condensed-matter realization of Majorana fermions. These quasiparticles are non-Abelian anyons and can be used for quantum information processing. There have been several proposals and experiments where topological superconductors are realized by building heterostructures. These heterostructures usually consist of an s-wave superconductor proximity-coupled to a semiconductor. In publication [P1] we explore the possibility of engineering a topological superconductor using a d-wave parent superconductor coupled to a two-dimensional electron gas with spin-orbit coupling and a Zeeman field. We determine an analytical expression of the Majorana states and compare these results to the ones obtained using a conventional s-wave superconductor...Fac. de Ciencias FísicasTRUEunpu
Optimized dynamical control of state transfer through noisy spin chains
We propose a method of optimally controlling the tradeoff of speed and
fidelity of state transfer through a noisy quantum channel (spin-chain). This
process is treated as qubit state-transfer through a fermionic bath. We show
that dynamical modulation of the boundary-qubits levels can ensure state
transfer with the best tradeoff of speed and fidelity. This is achievable by
dynamically optimizing the transmission spectrum of the channel. The resulting
optimal control is robust against both static and fluctuating noise in the
channel's spin-spin couplings. It may also facilitate transfer in the presence
of diagonal disorder (on site energy noise) in the channel.Comment: 20 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1310.162
From Quantum Optics to Quantum Technologies
Quantum optics is the study of the intrinsically quantum properties of light.
During the second part of the 20th century experimental and theoretical
progress developed together; nowadays quantum optics provides a testbed of many
fundamental aspects of quantum mechanics such as coherence and quantum
entanglement. Quantum optics helped trigger, both directly and indirectly, the
birth of quantum technologies, whose aim is to harness non-classical quantum
effects in applications from quantum key distribution to quantum computing.
Quantum light remains at the heart of many of the most promising and
potentially transformative quantum technologies. In this review, we celebrate
the work of Sir Peter Knight and present an overview of the development of
quantum optics and its impact on quantum technologies research. We describe the
core theoretical tools developed to express and study the quantum properties of
light, the key experimental approaches used to control, manipulate and measure
such properties and their application in quantum simulation, and quantum
computing.Comment: 20 pages, 3 figures, Accepted, Prog. Quant. Ele
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