2,888 research outputs found

    Link Fault Localization using Bi-directional M-Trails in All-Optical Mesh Networks

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    Gossip Algorithms for Distributed Signal Processing

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    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

    Anyon models in quantum codes and topological superconductors

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    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

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    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

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    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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