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Quantum-key-distribution (QKD) networks are gaining importance and it has become necessary to analyze the most appropriate methods for their long-distance interconnection. In this paper, four different methods of interconnecting remote QKD networks are proposed. The methods are used to link three different QKD testbeds in Europe, located in Berlin, Madrid, and Poznan. Although long-distance QKD links are only emulated, the methods used can serve as a blueprint for the secure interconnection of distant QKD networks in the future. Specifically, the presented approaches combine, in a transparent way, different fiber and satellite physical media, as well as common standards of key delivery interfaces. The testbed interconnections are designed to increase the security by utilizing multipath techniques and multiple hybridizations of QKD and post-quantum cryptography (PQC) algorithms.

Typically in many-body systems the correlation energy, which is defined as the difference between the exact ground state energy and the mean-field solution, has been a measure of the system's total correlations. However, under the quantum information context, it is possible to define some quantities in terms of the system's constituents that measure the classical and quantum correlations, such as the entanglement entropy, mutual information, quantum discord, one-body entropy, etc. In this work, we apply concepts of quantum information in fermionic systems in order to study traditional correlation measures (the relative correlation energy) from a novel approach. Concretely, we analyze the two and three level Lipkin models, which are exactly solvable (but non trivial) models very used in the context of the many-body problem.

Quantum based technologies have been fundamental in our world. After producing the laser and the transistor, the devices that have shaped our modern information society, the possibilities enabled by the ability to create and manipulate individual quantum states opens the door to a second quantum revolution. In this paper we explore the possibilities that these new technologies bring to the Telecommunications industry.

The convergence of quantum cryptography with applications used in everyday life is a topic drawing attention from the industrial and academic worlds. The development of quantum electronics has led to the practical achievement of quantum devices that are already available on the market and waiting for their first application on a broader scale. A major aspect of quantum cryptography is the methodology of Quantum Key Distribution (QKD), which is used to generate and distribute symmetric cryptographic keys between two geographically separate users using the principles of quantum physics. In previous years, several successful QKD networks have been created to test the implementation and interoperability of different practical solutions. This article surveys previously applied methods, showing techniques for deploying QKD networks and current challenges of QKD networking. Unlike studies focusing on optical channels and optical equipment, this survey focuses on the network aspect by considering network organization, routing and signaling protocols, simulation techniques, and a software-defined QKD networking approach.

Quantum key distribution (QKD) is a physical technology that enables the secure generation of bit streams (keys) in two separated locations. This technology is designed to provide a solution for very secure (quantum-safe) key agreement, which is nowadays at risk due to advances in quantum computing. The recent demonstration of a QKD network in the metropolitan area of Madrid shows how these networks can be deployed in current production infrastructure by following existing networking paradigms, such as software-defined networking. In particular, a three-node QKD network is implemented on the metropolitan area network using existing infrastructure and coexisting with other data and control services. On the other hand, telecommunication networks are drastically changing the way services are architectured. Users of the operator’s infrastructure are moving from traditional connectivity services (e.g., virtual private networks) to a set of interconnected network functions, either physical or virtual, in the shape of service function chaining (SFC). However, SFC users do not have a method to validate that the traffic flow is appropriately forwarded across the nodes in the network, a situation that may lead to very critical security breaches (e.g., a security node or a firewall in the chain that is bypassed). This work presents a method for validating ordered proof-of-transit (OPoT) on top of the Madrid Quantum Network. We first provide a general description of the QKD network deployed in Madrid. Then, we describe an existing security protocol for PoT in packet networks, analyzing its issues and vulnerabilities. Finally, this work presents a protocol for alleviating the security breach found in this work and for providing OPoT in SFC. Finally, an example of the real implementation is shown, where nodes being part of the OPoT scheme are provisioned with QKD-derived keys.

Quantum computers will change the cryptographic panorama. A technology once believed to lay far away into the future is increasingly closer to real world applications. Quantum computers will break the algorithms used in our public key infrastructure and in our key exchange protocols, forcing a complete retooling of the cryptography as we know it. Quantum Key distribution is a physical layer technology immune to quantum or classical computational threats. However, it requires a physical substrate, and optical fiber has been the usual choice. Most of the time used just as a point to point link for the exclusive transport of the delicate quantum signals. Its integration in a real-world shared network has not been attempted so far. Here we show how the new programmable software network architectures, together with specially designed quantum systems can be used to produce a network that integrates classical and quantum communications, including management, in a single, production-level infrastructure. The network can also incorporate new quantum-safe algorithms and use the existing security protocols, thus bridging the gap between today's network security and the quantum-safe network of the future. This can be done in an evolutionary way, without zero-day migrations and the corresponding upfront costs. We also present how the technologies have been deployed in practice using a production network.

La idea detrás de la realización de este trabajo de fin de grado es la de realizar un proceso de gamificación sobre algunos conceptos y elementos básicos de la información y computación cuántica para propiciar su enseñanza por parte de profesores y su aprendizaje por parte del alumnado. Dicho proceso de gamificación tendrá como objetivo el presentar de manera amigable y progresiva estos conceptos para permitir que se desarrolle intuición sobre ellos. La manera elegida para gamificar estos conceptos es mediante la realización de un videojuego con Unity que utilice la lógica y los principios del mundo del videojuego para poder cumplir con el objetivo mencionado anteriormente.---ABSTRACT---The main idea behind this final Project is to accomplish a gamification process with some concepts and basic ideas of quantic computation and quantic information to help college teachers and students. This gamification process will present in a friendly and progressive manner the main concepts so the student can develop an intuition about them. The technique chosen to gamify these concepts is a videogame developed with Unity that will use the logic and principles of the videogame world to accomplish the proposed objectives.

The nature of network services has drastically changed in recent years. New demands require new capabilities, forcing the infrastructure to dynamically adapt to new scenarios. Novel network paradigms, such as software-defined networking (SDN) and network functions virtualization, have appeared to provide flexibility for network management and services. The reliance on software and commoditized hardware of these new paradigms introduces new security threats and, consequently, one of the most desired capabilities is a strengthened security layer when connecting remote premises. On the other hand, traditional cryptographic protocols are based on computational complexity assumptions. They rely on certain mathematical problems (e.g., integer factorization, discrete logarithms, or elliptic curves) that cannot be efficiently solved using conventional computing. This general assumption is being revisited because of quantum computing. The creation of a quantum computer would put these protocols at risk and force a general overhaul of network security. Quantum key distribution (QKD) is a novel technique for providing synchronized sources of symmetric keys between two separated domains. Its security is based on the fundamental laws of quantum physics, which makes it impossible to copy the quantum states exchanged between both endpoints. Therefore, if implemented properly, QKD generates highly secure keys, immune to any algorithmic cryptanalysis. This work proposes a node design to provide QKD-enhanced security in end-to-end services and analyze the control plane requirements for service provisioning in transport networks. We define and demonstrate the necessary workflows and protocol extensions in different SDN scenarios, integrating the proposed solution into a virtual router providing QKD-enhanced IPsec sessions. security in end-to-end services and analyze the control plane requirements for service provisioning in transport networks. We define and demonstrate the necessary w

En este proyecto se realiza un estudio de técnicas de visualización científica colaborativa y métodos de comunicación interactiva, además del estudio del entorno de trabajo. Así mismo se desarrolla una infraestructura compuesta de una herramienta de visualización científica implementada sobre el motor de juegos Unreal Engine, un sistema de persistencia y un servicio web RESTful para la gestión de la persistencia, que además proporciona una interfaz gráfica para la extracción de información producida dentro de la herramienta de análisis. Finalmente se obtiene como resultado un sistema que proporcionará a investigadores la capacidad de colaborar en estudios de análisis de escenas neurocientíficas dentro de la iniciativa Human Brain Project (HBP).---ABSTRACT---This project bring out a study of collaborative scientific visualization techniques and interactive communication methods, as well as the study of the work environment. Also it has been developed is an infrastructure composed of a scientific visualization tool implemented on the Unreal Engine game engine, a persistence system and a RESTful web service for the management of persistence, which also provides a graphical interface for the extraction of information produced within the analysis tool. Finally, the result is a system that will provide researchers with the ability to collaborate in neuroscientific scene analysis studies within the Human Brain Project (HBP).

El cerebro humano es el órgano más complejo y a la vez, el más desconocido que poseen los seres humanos. Este órgano define los rasgos de personalidad, el pensamiento, las emociones y las memorias, y todo aquello que define a un ser humano como persona. Sin embargo, su estructura, organización y funcionamiento aún suponen un gran desafío para la comunidad científica. Gracias a los últimos avances de las diferentes instituciones neurocientíficas, potenciadas por el progreso de la tecnología, esta meta está más cerca que nunca. Dentro de este ámbito, en los últimos años han surgido numerosas iniciativas para intentar acercarse a esta meta. "The Human Brain Project", "Blue Brain Project" o el "Brain Iniatiative" son algunos de los proyectos que han intentado aunar el conocimiento de diferentes instituciones pertenecientes a un alto rango de disciplinas, para el desarrollo de nuevas técnicas y tecnologías para el estudio del cerebro humano. Entre estos proyectos, el Human Brain Project destaca como uno de los mayores proyectos de investigación financiado por la Unión Europea, siendo a su vez el marco en el que se desarrolla el presente trabajo de fin de grado. La finalidad de este TFG consiste en la mejora de las representaciones existentes en MSPViz para su adaptación a los principios de visualización, así como, la creación de nuevas vistas y representaciones de carácter neurocientífico destinadas a la visualización de datos provenientes de simulaciones de modelos de plasticidad estructural. Junto con este desarrollo, se ha mejorado la herramienta MSPViz y se han creado nuevas rutas de análisis dentro de la misma.---ABSTRACT---The human brain is the most complex organ and at the same time the one that is still mostly unknown. It defines our personality, our thoughts, our emotions and memories, and everything else that shapes the human being as a person. Nevertheless, its structure, organization and operation still constitute a challenge for the scientific community now

En este documento se realiza un análisis de viabilidad de la utilización del motor de videojuegos Unreal Engine 4 (UE4) en el diseño e implementación de herramientas de visualización científica, orientadas principalmente a las necesidades del proyecto Human Brain Project (HBP). El presente documento se compone de tres bloques: El bloque 1 consta de una introducción a la visualización científica y al motor de juegos UE4, centrándonos en las áreas del motor que tienen impacto en los objetivos propuestos. En el bloque 2 se hace una descripción del diseño e implementación de la herramienta de análisis. El bloque concluirá con una batería de pruebas y demostraciones de la herramienta implementada detallando sus principales características. En último lugar en el bloque 3 se hace una valoración del motor de juegos UE4 para el desarrollo de herramientas de visualización científica desde distintos puntos de vista, como la eficiencia en el tiempo de implementación y comparación con otras alternativas.---ABSTRACT---A viability analysis about the use of the Unreal Engine 4 (UE4), a videogame engine, is done in this document. What is analyzed here is the design and the implementation of a set of tools of scientific visualization, mainly oriented to the needs of the Human Brain Project (HBP). The present document is compounded by three parts: The former one consists of an introduction to the scientific visualization and to the game engine UE4, focusing on the areas that are more related to the objectives that had been proposed. A description of the design and implementation of the analysis tool is made in the second part. This part concludes with a set of tests and demonstrations of the implemented tool, detailing its main features. Finally, an evaluation of the use of the game engine UE4 for the development of scientific visualization tools is made in the third part. This evaluation is made from different points of view, such as the efficiency of the time of implementation or th

El proyecto aquí presentado persigue un objetivo que puede ser resumido en la realización de una aplicación web enriquecida (RIA) orientada a la visualización científica. Dentro de la visualización científica, el área donde se va a enmarcar el proyecto es la neurociencia. Esto se debe a que este trabajo se encuentra enmarcado bajo una iniciativa de carácter internacional llamada Human Brain Project (HBP). Esta gran iniciativa persigue el fin de poder simular por completo un cerebro humano dentro de un supercomputador. Para ello precisa de la colaboración de varias ramas de la ciencia, entre ellas, la computación científica que es donde esta contextualizado mi proyecto. Es por ello que el fin último del proyecto, es poder visualizar elementos de carácter neurocientífico, ya sea de forma esquemática o realista, mediante tecnología web. La idea consiste en crear una aplicación web capaz de representar visualizaciones, ya sea de manera esquemática en 2D mediante imágenes vectoriales o de manera realista en 3D mediante WebGl. Profundizando un poco más en el objetivo del proyecto, a parte de la visualización de elementos mediante tecnología web, también se plantea la necesidad de hacer que se actualicen estas visualizaciones de forma dinámica con datos recibidos por red. Esto supone establecer una comunicación por red con un sistema que proporcione datos de una simulación para que puedan ser recibidos y actualizar el modelo de forma dinámica. Para probar la funcionalidad descrita, se han realizado dos pruebas de concepto que demuestran la capacidad de la aplicación de representar elementos 2D y 3D mediante tecnología web y pudiendo manipular estas visualizaciones de forma dinámica con los paquetes de datos recibidos por red.---ABSTRACT---This Project follows one objective that can be summarised briefly in the development of a Rich Internet Application (RIA) oriented to scientific visualization. Within scientific visualization, the field in which this project is embedded

The ability to generate entangled photon pairs over a broad wavelength range opens the door to the simultaneous distribution of entanglement to multiple users in a network by using centralized sources and flexible wavelength-division multiplexing schemes. Here, we show the design of a metropolitan optical network consisting of tree-type access networks, whereby entangled photon pairs are distributed to any pair of users, independent of their location. The network is constructed employing commercial off-the-shelf components and uses the existing infrastructure, which allows for moderate deployment costs. We further develop a channel plan and a network-architecture design to provide a direct optical path between any pair of users; thus, allowing classical and one-way quantum communication, as well as entanglement distribution. This allows the simultaneous operation of multiple quantum information technologies. Finally, we present a more flexible backbone architecture that pushes away the load limitations of the original network design by extending its reach, number of users and capabilities.

Cascade is an information reconciliation protocol proposed in the context of secret key agreement in quantum cryptography. This protocol allows removing discrepancies in two partially correlated sequences that belong to distant parties, connected through a public noiseless channel. It is highly interactive, thus requiring a large number of channel communications between the parties to proceed and, although its efficiency is not optimal, it has become the de-facto standard for practical implementations of information reconciliation in quantum key distribution. The aim of this work is to analyze the performance of Cascade, to discuss its strengths, weaknesses and optimization possibilities, comparing with some of the modified versions that have been proposed in the literature. When looking at all design trade-offs, a new view emerges that allows to put forward a number of guidelines and propose near optimal parameters for the practical implementation of Cascade improving performance significantly in comparison with all previous proposals.

Se puede simular sobre un computador digital o clásico el modo de computar de un computador cuántico. En este trabajo realizo un estudio de los conceptos más fundamentales del paradigma de la computación cuántica. Además describo las tecnologías con las que se pretende llevar a cabo este modelo de computación. Pongo en práctica dicho contenido teórico y mis aptitudes adquiridas durante mis estudios realizando un simulador que desarrolla un algoritmo cuántico: el algoritmo de Shor. Describo las características de dicho simulador, señalando aquellas que no se ajusten por algún motivo. Por último obtengo mis conlusiones tras el desarrollo de todo el trabajo.---ABSTRACT---It is possible to simulate on a classic or digital computer a quantum computer computing mode. I have made a study on the main concepts of this paradigm of computing in this report. Additionally, I explain the technologies to carry out this computing model. I put into practice the theoretical content and my skills acquired during my studies when performing a quantum simulator. I have developed a quantum algorithm on it: Shor's algorithm. I have described this simulator specifications, pointing out those that do not conform to the reality. Finally, I have obtained my own conclusion after the whole work.

Quantum Key Distribution (QKD) is maturing quickly. However, the current approaches to its application in optical networks make it an expensive technology. QKD networks deployed to date are designed as a collection of point-to-point, dedicated QKD links where non-neighboring nodes communicate using the trusted repeater paradigm. We propose a novel optical network model in which QKD systems share the communication infrastructure by wavelength multiplexing their quantum and classical signals. The routing is done using optical components within a metropolitan area which allows for a dynamically any-to-any communication scheme. Moreover, it resembles a commercial telecom network, takes advantage of existing infrastructure and utilizes commercial components, allowing for an easy, cost-effective and reliable deployment.

One of the main obstacles to the widespread adoption of quantum cryptography has been the difficulty of integration into standard optical networks, largely due to the tremendous difference in power of classical signals compared with the single quantum used for quantum key distribution. This makes the technology expensive and hard to deploy. In this letter, we show an easy and straightforward integration method of quantum cryptography into optical access networks. In particular, we analyze how a quantum key distribution system can be seamlessly integrated in a standard access network based on the passive optical and time division multiplexing paradigms. The novelty of this proposal is based on the selective post-processing that allows for the distillation of secret keys avoiding the noise produced by other network users. Importantly, the proposal does not require the modification of the quantum or classical hardware specifications neither the use of any synchronization mechanism between the network and quantum cryptography devices.

La finalidad de este proyecto es la de estudiar las alternativas empleadas hoy en día para asegurar y garantizar el correcto acceso a infraestructuras sensibles, evitando el uso de las clásicas passwords por los problemas que acarrean, detallados en el apartado 2.2. Autenticación mediante passwords y problemas en su uso. Se analizarán y estudiarán algunas de las soluciones más factibles para garantizar un correcto acceso a sistemas sensibles, destacando las ventajas y problemas de cada una de las soluciones. Con esto se quiere decir que no se tratará de solucionar los problemas de seguridad y gestión de acceso a la hora de acceder a las diversas plataformas web, como puedan ser redes sociales o sistemas de pago y/o transacciones. El estudio se va a limitar al caso dado en el centro de supercomputación CeSViMa, pudiéndose extender a cualquier infraestructura física, siempre y cuando se tenga en cuenta que para el acceso a la infraestructura se pueden necesitar medios o periféricos hardware que, obviamente, serán controlados por la empresa o sistema alojado en dicha infraestructura. Tras dicho estudio, se procederá al diseño de la que se considere mejor opción en una instalación real. El estudio del sistema se llevará a cabo, tal y como se ha mencionado, en el centro de supercomputación CeSViMa ubicado en el Campus Montegancedo.

—In this paper we explore how recent technologies can improve the security of optical networks. In particular, we study how to use quantum key distribution(QKD) in common optical network infrastructures and propose a method to overcome its distance limitations. QKD is the first technology offering information theoretic secretkey distribution that relies only on the fundamental principles of quantum physics. Point-to-point QKDdevices have reached a mature industrial state; however, these devices are severely limited in distance, since signals at the quantum level (e.g., single photons) are highly affected by the losses in the communication channel and intermediate devices. To overcome this limitation, intermediate nodes (i.e., repeaters) are used. Both quantum-regime and trusted, classical repeaters have been proposed in the QKD literature, but only the latter can be implemented in practice. As a novelty, we propose here a new QKD network model based on the use of not fully trusted intermediate nodes, referred to as weakly trusted repeaters. This approach forces the attacker to simultaneously break several paths to get access to the exchanged key, thus improving significantly the security of the network. We formalize the model using network codes and provide real scenarios that allow users to exchange secure keys over metropolitan optical networks using only passive components. Moreover, the theoretical framework allows one to extend these scenarios not only to accommodate more complex trust constraints, but also to consider robustness and resiliency constraints on the network.

Quantum key distribution performs the trick of growing a secret key in two distant places connected by a quantum channel. The main reason is so that the legitimate users can bound the information gathered by the eavesdropper. In practical systems, whether because of finite resources or external conditions, the quantum channel is subject to fluctuations. A rate-adaptive information reconciliation protocol, which adapts to the changes in the communication channel, is then required to minimize the leakage of information in the classical postprocessing. We consider here the leakage of a rate-adaptive information reconciliation protocol. The length of the exchanged messages is larger than that of an optimal protocol; however, we prove that the min-entropy reduction is limited. The simulation results, both in the asymptotic and in the finite-length regime, show that this protocol allows to increase the amount of a distillable secret key.

Quantum Key Distribution is carving its place among the tools used to secure communications. While a difficult technology, it enjoys benefits that set it apart from the rest, the most prominent is its provable security based on the laws of physics. QKD requires not only the mastering of signals at the quantum level, but also a classical processing to extract a secret-key from them. This postprocessing has been customarily studied in terms of the efficiency, a figure of merit that offers a biased view of the performance of real devices. Here we argue that it is the throughput the significant magnitude in practical QKD, specially in the case of high speed devices, where the differences are more marked, and give some examples contrasting the usual postprocessing schemes with new ones from modern coding theory. A good understanding of its implications is very important for the design of modern QKD devices.

Puncturing is a well-known coding technique widely used for constructing rate-compatible codes. In this paper, we consider the problem of puncturing low-density parity-check codes and propose a new algorithm for intentional puncturing. The algorithm is based on the puncturing of untainted symbols, i.e. nodes with no punctured symbols within their neighboring set. It is shown that the algorithm proposed here performs better than previous proposals for a range of coding rates and short proportions of punctured symbols.

The progressive edge-growth algorithm is a well-known procedure to construct regular and irregular low-density parity-check codes. In this paper, we propose a modification of the original algorithm that improves the performance of these codes in the waterfall region when constructing codes complying with both, check and symbol node degree distributions. The proposed algorithm is thus interesting if a family of irregular codes with a complex check node degree distribution is used.

El mundo de la tecnología impregna cada día más la sociedad actual, hasta el punto de que siempre que utilizamos el término información lo relacionamos directamente con un ordenador o un dispositivo de almacenamiento. Aunque este uso sea válido, podemos ver que la información está asociada a muchos otros campos de la naturaleza. La genética o, como veremos en este proyecto, la física, son algunos de esos campos. Podemos afirmar, en consecuencia, que la teoría de la información no es una disciplina exclusiva de la ingeniería, siendo también una herramienta fundamental para otras ramas de la ciencia. Pero existe algo todavía más interesante en la implementación física de la información, y es la posibilidad real de extender el átomo básico de información, bit, al qubit, una nueva magnitud que contiene a la antigua y evoluciona con nuevas reglas dictadas por la física cuántica. Su uso nos conduce a los ordenadores cuánticos y más concretamente a lo que será el tema de este proyecto: los sistemas de criptografía.