132 research outputs found
Entanglement of distant atoms for quantum networks
Quantennetze versprechen viele revolutionäre Anwendungen, wie zum Beispiel sichere Quantenkommunikation und verteiltes Quantencomputing. Im Mittelpunkt dieser Netze steht die Fähigkeit, die Verschränkung zwischen weit entfernten Knoten über photonische Kanäle zu verteilen. Verschiedene physikalische Kandidaten werden aktiv erforscht, um als Quantensystem in den Knoten zu dienen. Hier verwenden wir neutrale Einzelatome, um eine Quantennetzwerkverbindung zwischen zwei unabhängigen Knoten zu realisieren, die sich in 400 m voneinander entfernten Gebäuden befinden. Diese Arbeit konzentriert sich auf zwei Themen, die Demonstration eines geräteunabhängigen Quantenschlüsselverteilungsprotokolls und die Verschränkungsverteilung zwischen den Knoten über Dutzende von Kilometern Telekommunikationsfaser mit Hilfe von Quantenfrequenzumwandlung.
Die geräteunabhängige Quantenschlüsselverteilung ermöglicht die Erzeugung geheimer Schlüssel über einen nicht vertrauenswürdigen Kanal unter Verwendung nicht charakterisierter und potenziell nicht vertrauenswürdiger Geräte. Das ordnungsgemäße und sichere Funktionieren der Geräte kann durch einen statistischen Test mit einer Bell-Ungleichung bestätigt werden, so dass nur noch die Integrität der Nutzerstandorte mit anderen Mitteln garantiert werden muss. Die Realisierung geräteunabhängiger Protokolle stellt jedoch eine Herausforderung dar—hauptsächlich da es schwierig ist hochwertige verschränkte Zustände zwischen zwei entfernten Orten mit hoher Detektionseffizienz herzustellen. Hier stellen wir ein experimentelles System vor, das die Verteilung von Quantenschlüsseln in einem völlig geräteunabhängigen Szenario ermöglicht. Indem wir eine ereignisbereite Atom-Atom-Verschränkungstreue von F>0.892(23) erreichen, beobachten wir eine signifikante Verletzung der CHSH-Bell-Ungleichung von S=2.578(75)—oberhalb der klassischen Grenze von 2—und eine Quantenbitfehlerrate von 0.078(9). Für das implementierte Protokoll mit Zufallsschlüsseln ergibt sich daraus eine Geheimschlüsselrate von 0.07 Bit pro Verschränkungsereignis im asymptotischen Limit, was die Fähigkeit des Systems zur Erzeugung von Geheimschlüsseln in einem geräteunabhängigen Szenario demonstriert.
Das zweite Thema ist die Verschränkungsverteilung über große Entfernungen mit optische Fasern, für die es unerlässlich ist, bei Telekommunikationswellenlängen zu arbeiten, um hohe Dämpfungsverluste zu überwinden. Die meisten Quantensysteme, die derzeit erforscht werden, arbeiten jedoch im sichtbaren Licht oder nahen Infrarot. Wir verwenden eine polarisationserhaltende Quantenfrequenzumwandlung in beiden Knotenpunkten, um die Wellenlänge der mit den Atomen verschränkten Photonen von 780 nm in das S-Band der Telekommunikation zu transformieren. Dank einer beispiellosen Effizienz der externen Konversion von 57% und minimalem induziertem Rauschen berichten wir über die Beobachtung von Atom-Photon- und angekündigter Atom-Atom-Verschränkung, die über Telekom-Glasfaserverbindungen mit einer Länge von bis zu 33 km erzeugt wurde. Wir analysieren die Verschränkungstreue für verschiedene Glasfaserverbindungslängen und zeigen, dass diese bei längeren Verbindungen hauptsächlich durch die atomare Dekohärenz begrenzt ist. Die Atom-Atom-Verschränkung wird erst nach dem Empfang des Ankündigungssignals analysiert, das eine Zeitverzögerung enthält, um die klassischen Kommunikationszeiten zwischen den Knoten zu berücksichtigen und ein realistisches Szenario einer Quantennetzwerkverbindung zu simulieren.
Die in dieser Arbeit vorgestellten Ergebnisse ebnen den Weg zur ultimativen Form der sicheren Quantenkommunikation in zukünftigen Quantennetzwerken und sind ein Meilenstein auf dem Weg zur Realisierung von Quantennetzwerkverbindungen über große Entfernungen.Quantum networks promise many revolutionary applications, such as secure quantum communication and distributed quantum computing. Central to these networks is the ability to distribute entanglement between distant nodes using photonic channels. Various physical candidates are under active research to serve as quantum system in the nodes. Here, we employ neutral single-atoms to realise a quantum network link between two independent nodes located in buildings 400 m apart. This thesis focusses on two topics, namely, the demonstration of a device-independent quantum key distribution protocol and entanglement distribution between the nodes over tens of kilometres of telecom fibre employing quantum frequency conversion.
Device-independent quantum key distribution enables the generation of secret keys over an untrusted channel using uncharacterized and potentially untrusted devices. The proper and secure functioning of the devices can be certified by a statistical test probing a Bell inequality, thereby leaving only the integrity of the users' locations to be guaranteed by other means. The realisation of device-independent protocols, however, is challenging—mainly because it is difficult to establish high-quality entangled states between two remote locations with high detection efficiency. Here we present an experimental system that allows for quantum key distribution in a fully device-independent setting. By achieving an event-ready atom-atom entanglement fidelity of F>0.892(23), we observe a significant violation of a CHSH Bell inequality of S=2.578(75)—above the classical limit of 2—and a quantum bit error rate of 0.078(9). For the implemented random key-bases protocol, this results in a secret key rate of 0.07 bits per entanglement generation event in the asymptotic limit, and thus demonstrates the system's capability to generate secret keys in a device-independent setting.
The second topic is long-distance entanglement distribution over optical fibres, for which it is essential to operate at telecom wavelengths to overcome high attenuation losses. Most quantum system under active research, however, operate in the visible or near infrared. We employ polarization-preserving quantum frequency conversion in both nodes to transform the wavelength of the photons that are entangled with the atoms from 780 nm to the telecom S band. Enabled by an unprecedented external device conversion efficiency of 57% and minimal induced noise, we report on the observation of atom-photon and heralded atom-atom entanglement generated over telecom fibre links with a length up to 33 km. We analyse the entanglement fidelity for different fibre link lengths and show that for longer links the fidelity is mainly limited by atomic decoherence. The atom-atom entanglement is analysed only after receiving the heralding signal including a time delay to account for classical communication times between the nodes to simulate a realistic quantum network link scenario.
The results presented in this thesis pave the way towards the ultimate form of quantum secure communications in future quantum networks and are a milestone on the road to realise long-distance quantum network links
Improving Data Availability in Decentralized Storage Systems
PhD thesis in Information technologyPreserving knowledge for future generations has been a primary concern for humanity since the dawn of civilization. State-of-the-art methods have included stone carvings, papyrus scrolls, and paper books. With each advance in technology, it has become easier to record knowledge. In the current digital age, humanity may preserve enormous amounts of knowledge on hard drives with the click of a button.
The aggregation of several hard drives into a computer forms the basis for a storage system. Traditionally, large storage systems have comprised many distinct computers operated by a single administrative entity.
With the rise in popularity of blockchain and cryptocurrencies, a new type of storage system has emerged. This new type of storage system is fully decentralized and comprises a network of untrusted peers cooperating to act as a single storage system. During upload, files are split into chunks and distributed across a network of peers. These storage systems encode files using Merkle trees, a hierarchical data structure that provides integrity verification and lookup services.
While decentralized storage systems are popular and have a user base in the millions, many technical aspects are still in their infancy. As such, they have yet to prove themselves viable alternatives to traditional centralized storage systems.
In this thesis, we contribute to the technical aspects of decentralized storage systems by proposing novel techniques and protocols. We make significant contributions with the design of three practical protocols that each improve data availability in different ways.
Our first contribution is Snarl and entangled Merkle trees. Entangled Merkle trees are resilient data structures that decrease the impact hierarchical dependencies have on data availability. Whenever a chunk loss is detected, Snarl uses the entangled Merkle trees to find parity chunks to repair the lost chunk. Our results show that by encoding data as an entangled Merkle tree and using Snarl’s repair algorithm, the storage utilization in current systems could be improved by over five times, with improved data availability.
Second, we propose SNIPS, a protocol that efficiently synchronizes the data stored on peers to ensure that all peers have the same data. We designed a Proof of Storage-like construction using a Minimal Perfect Hash Function. Each peer uses the PoS-like construction to create a storage proof for those chunks it wants to synchronize. Peers exchange storage proofs and use them to efficiently determine which chunks they are missing. The evaluation shows that by using SNIPS, the amount of synchronization data can be reduced by three orders of magnitude in current systems.
Lastly, in our third contribution, we propose SUP, a protocol that uses cryptographic proofs to check if a chunk is already stored in the network before doing wasteful uploads. We show that SUP may reduce the amount of data transferred by up to 94 % in current systems.
The protocols may be deployed independently or in combination to create a decentralized storage system that is more robust to major outages. Each of the protocols has been implemented and evaluated on a large cluster of 1,000 peers
Systematic Approaches for Telemedicine and Data Coordination for COVID-19 in Baja California, Mexico
Conference proceedings info:
ICICT 2023: 2023 The 6th International Conference on Information and Computer Technologies
Raleigh, HI, United States, March 24-26, 2023
Pages 529-542We provide a model for systematic implementation of telemedicine within a large evaluation center for COVID-19 in the area of Baja California, Mexico. Our model is based on human-centric design factors and cross disciplinary collaborations for scalable data-driven enablement of smartphone, cellular, and video Teleconsul-tation technologies to link hospitals, clinics, and emergency medical services for point-of-care assessments of COVID testing, and for subsequent treatment and quar-antine decisions. A multidisciplinary team was rapidly created, in cooperation with different institutions, including: the Autonomous University of Baja California, the Ministry of Health, the Command, Communication and Computer Control Center
of the Ministry of the State of Baja California (C4), Colleges of Medicine, and the College of Psychologists. Our objective is to provide information to the public and to evaluate COVID-19 in real time and to track, regional, municipal, and state-wide data in real time that informs supply chains and resource allocation with the anticipation of a surge in COVID-19 cases. RESUMEN Proporcionamos un modelo para la implementación sistemática de la telemedicina dentro de un gran centro de evaluación de COVID-19 en el área de Baja California, México. Nuestro modelo se basa en factores de diseño centrados en el ser humano y colaboraciones interdisciplinarias para la habilitación escalable basada en datos de tecnologías de teleconsulta de teléfonos inteligentes, celulares y video para vincular hospitales, clínicas y servicios médicos de emergencia para evaluaciones de COVID en el punto de atención. pruebas, y para el tratamiento posterior y decisiones de cuarentena. Rápidamente se creó un equipo multidisciplinario, en cooperación con diferentes instituciones, entre ellas: la Universidad Autónoma de Baja California, la Secretaría de Salud, el Centro de Comando, Comunicaciones y Control Informático.
de la Secretaría del Estado de Baja California (C4), Facultades de Medicina y Colegio de Psicólogos. Nuestro objetivo es proporcionar información al público y evaluar COVID-19 en tiempo real y rastrear datos regionales, municipales y estatales en tiempo real que informan las cadenas de suministro y la asignación de recursos con la anticipación de un aumento de COVID-19. 19 casos.ICICT 2023: 2023 The 6th International Conference on Information and Computer Technologieshttps://doi.org/10.1007/978-981-99-3236-
PROCEEDINGS 5th PLATE Conference
The 5th international PLATE conference (Product Lifetimes and the Environment) addressed product lifetimes in the context of sustainability. The PLATE conference, which has been running since 2015, has successfully been able to establish a solid network of researchers around its core theme. The topic has come to the forefront of current (political, scientific & societal) debates due to its interconnectedness with a number of recent prominent movements, such as the circular economy, eco-design and collaborative consumption. For the 2023 edition of the conference, we encouraged researchers to propose how to extend, widen or critically re-construct thematic sessions for the PLATE conference, and the paper call was constructed based on these proposals. In this 5th PLATE conference, we had 171 paper presentations and 238 participants from 14 different countries. Beside of paper sessions we organized workshops and REPAIR exhibitions
Estudo do IPFS como protocolo de distribuição de conteúdos em redes veiculares
Over the last few years, vehicular ad-hoc networks (VANETs) have been the
focus of great progress due to the interest in autonomous vehicles and in
distributing content not only between vehicles, but also to the Cloud. Performing
a download/upload to/from a vehicle typically requires the existence
of a cellular connection, but the costs associated with mobile data transfers
in hundreds or thousands of vehicles quickly become prohibitive. A VANET
allows the costs to be several orders of magnitude lower - while keeping the
same large volumes of data - because it is strongly based in the communication
between vehicles (nodes of the network) and the infrastructure.
The InterPlanetary File System (IPFS) is a protocol for storing and distributing
content, where information is addressed by its content, instead of
its location. It was created in 2014 and it seeks to connect all computing
devices with the same system of files, comparable to a BitTorrent swarm
exchanging Git objects. It has been tested and deployed in wired networks,
but never in an environment where nodes have intermittent connectivity,
such as a VANET. This work focuses on understanding IPFS, how/if it can
be applied to the vehicular network context, and comparing it with other
content distribution protocols.
In this dissertation, IPFS has been tested in a small and controlled network
to understand its working applicability to VANETs. Issues such as neighbor
discoverability times and poor hashing performance have been addressed.
To compare IPFS with other protocols (such as Veniam’s proprietary solution
or BitTorrent) in a relevant way and in a large scale, an emulation platform
was created. The tests in this emulator were performed in different times of
the day, with a variable number of files and file sizes. Emulated results show
that IPFS is on par with Veniam’s custom V2V protocol built specifically for
V2V, and greatly outperforms BitTorrent regarding neighbor discoverability
and data transfers.
An analysis of IPFS’ performance in a real scenario was also conducted, using
a subset of STCP’s vehicular network in Oporto, with the support of
Veniam. Results from these tests show that IPFS can be used as a content
dissemination protocol, showing it is up to the challenge provided by a
constantly changing network topology, and achieving throughputs up to 2.8
MB/s, values similar or in some cases even better than Veniam’s proprietary
solution.Nos últimos anos, as redes veiculares (VANETs) têm sido o foco de grandes
avanços devido ao interesse em veículos autónomos e em distribuir conteúdos,
não só entre veículos mas também para a "nuvem" (Cloud). Tipicamente,
fazer um download/upload de/para um veículo exige a utilização
de uma ligação celular (SIM), mas os custos associados a fazer transferências
com dados móveis em centenas ou milhares de veículos rapidamente se
tornam proibitivos. Uma VANET permite que estes custos sejam consideravelmente
inferiores - mantendo o mesmo volume de dados - pois é fortemente
baseada na comunicação entre veículos (nós da rede) e a infraestrutura.
O InterPlanetary File System (IPFS - "sistema de ficheiros interplanetário")
é um protocolo de armazenamento e distribuição de conteúdos, onde a informação
é endereçada pelo conteúdo, em vez da sua localização. Foi criado
em 2014 e tem como objetivo ligar todos os dispositivos de computação num
só sistema de ficheiros, comparável a um swarm BitTorrent a trocar objetos
Git. Já foi testado e usado em redes com fios, mas nunca num ambiente
onde os nós têm conetividade intermitente, tal como numa VANET. Este
trabalho tem como foco perceber o IPFS, como/se pode ser aplicado ao
contexto de rede veicular e compará-lo a outros protocolos de distribuição
de conteúdos.
Numa primeira fase o IPFS foi testado numa pequena rede controlada, de
forma a perceber a sua aplicabilidade às VANETs, e resolver os seus primeiros
problemas como os tempos elevados de descoberta de vizinhos e o fraco desempenho
de hashing.
De modo a poder comparar o IPFS com outros protocolos (tais como a
solução proprietária da Veniam ou o BitTorrent) de forma relevante e em
grande escala, foi criada uma plataforma de emulação. Os testes neste emulador
foram efetuados usando registos de mobilidade e conetividade veicular
de alturas diferentes de um dia, com um número variável de ficheiros e
tamanhos de ficheiros. Os resultados destes testes mostram que o IPFS está
a par do protocolo V2V da Veniam (desenvolvido especificamente para V2V
e VANETs), e que o IPFS é significativamente melhor que o BitTorrent no
que toca ao tempo de descoberta de vizinhos e transferência de informação.
Uma análise do desempenho do IPFS em cenário real também foi efetuada,
usando um pequeno conjunto de nós da rede veicular da STCP no Porto,
com o apoio da Veniam. Os resultados destes testes demonstram que o
IPFS pode ser usado como protocolo de disseminação de conteúdos numa
VANET, mostrando-se adequado a uma topologia constantemente sob alteração,
e alcançando débitos até 2.8 MB/s, valores parecidos ou nalguns
casos superiores aos do protocolo proprietário da Veniam.Mestrado em Engenharia de Computadores e Telemátic
On the Design of Future Communication Systems with Coded Transport, Storage, and Computing
Communication systems are experiencing a fundamental change. There are novel applications that require an increased performance not only of throughput but also latency, reliability, security, and heterogeneity support from these systems. To fulfil the requirements, future systems understand communication not only as the transport of bits but also as their storage, processing, and relation. In these systems, every network node has transport storage and computing resources that the network operator and its users can exploit through virtualisation and softwarisation of the resources. It is within this context that this work presents its results. We proposed distributed coded approaches to improve communication systems. Our results improve the reliability and latency performance of the transport of information. They also increase the reliability, flexibility, and throughput of storage applications. Furthermore, based on the lessons that coded approaches improve the transport and storage performance of communication systems, we propose a distributed coded approach for the computing of novel in-network applications such as the steering and control of cyber-physical systems. Our proposed approach can increase the reliability and latency performance of distributed in-network computing in the presence of errors, erasures, and attackers
Матеріали 4-го семінару молодих вчених з комп'ютерних наук та програмної інженерії (CS&SE@SW 2021), віртуальний захід, м. Кривий Ріг, Україна, 18 грудня 2021 р.
Матеріали 4-го семінару молодих вчених з комп'ютерних наук та програмної інженерії (CS&SE@SW 2021), віртуальний захід, м. Кривий Ріг, Україна, 18 грудня 2021 р.Proceedings of the 4th Workshop for Young Scientists in Computer Science & Software Engineering (CS&SE@SW 2021), Virtual Event, Kryvyi Rih, Ukraine, December 18, 2021
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