Nonlocal Entanglement Transformations Achievable by Separable Operations

For manipulations of multipartite quantum systems, it was well known that all local operations assisted by classical communication (LOCC) constitute a proper subset of the class of separable operations. Recently, Gheorghiu and Griffiths found that LOCC and general separable operations are equally powerful for transformations between bipartite pure states. In this letter we extend this comparison to mixed states and show that in general separable operations are strictly stronger than LOCC when transforming a mixed state to a pure entangled state. A remarkable consequence of our finding is the existence of entanglement monotone which may increase under separable operations.Comment: v2 has rephrased Theorem 1 and corrected Kraus operators in Theorem 2. Additional comments are welcome

Analysis of cryptocurrencies as a financial asset

Treball Final de Grau en Finances i Comptabilitat. Codi: FC1049. Curs acadèmic: 2020-2021The following research paper focuses on the analysis of new decentralized digital assets, cryptocurrencies. As an introduction, the concept of cryptocurrencies and the most outstanding references will be put into context. The main objective of the work is to analyze cryptocurrencies not only as a decentralized tool, but also as a speculative financial asset. Research will be conducted on the functioning of the reference currency, Bitcoin and the main factors affecting to understand how its value fluctuates. Subsequently, it will be compared with the coins that currently belong to the top 5 cryptocurrencies with the largest market capitalization

Quasi-periodic solutions in quasi-periodic systems via Fourier transforms

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2018, Director: Àlex Haro[eng] Within the field of dynamical systems, one shall find a special sort of systems, systems that revolve around external perturbations, either periodic or quasi-periodic, the so called skew-product dynamical systems. Even though the study of these systems can be a very helpful source of tools for an engineering or more practical work that may present systems alike, the main focus of this project is of a more theoretical nature. What is about to be presented is an approach to response solutions of such perturbated systems and the proof of existence and uniqueness of invariant fiberwise hyperbolic tori given an approximate torus of such characteristics, and the further expression of the proof’s conditions in computable terms via Fourier transforms. Besides the theoretical part, it is also provided an algorithm and its respective computational implementation that allows to simplify the expression of the linear dynamics of a system under a quasi-periodic perturbation into a diagonal matrix at the cost of an error that will significantly decrease at each step of the algorithm

Comparison of the AQO and the QAOA for the vertex coloring problem

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2023, Tutors: Marta P. Estarellas, Jordi Riu, Lluís GarridoWe benchmark the time resources needed to execute the adiabatic quantum optimization (AQO), and to run the Quantum Approximate Optimization Algorithm (QAOA), for the vertex coloring problem. This is done via a numerical simulation of 20 Erd˝os-R´eny random graphs for different cases ranging from 8 to 21 qubits. With this comparison, we explore two of the most important algorithms of the analog and gate-based quantum computing paradigms, respectively. We apply the canonical implementation for both algorithms, so their initial Hamiltonian is the same, the one with the typical sum of Pauli-X matrices. In this line, we consider linear scheduling time for the AQO. For final adiabatic time T = 100 ns, the AQO achieves an overlap with the degenerate solutions over 0.9 in all cases. Meanwhile, the QAOA using the Powell classical optimizer, 5 layers and thousands of iterations has an overlap around 0.5 for the 8 qubits case and below 0.25 for the other cases. So, our results for the given task and idealized conditions indicate that the AQO significantly outperforms the QAOA in terms of time and success probabilit

Existence of invariant tori in skew-product systems: A computer assisted approach

This work is a computer assisted approach to the study of invariant manifolds in skew-product dynamical systems. More specifically, the existence of an invariant tori under a quasi-periodic perturbation of our system. The goal is to use a computer to prove the theorem that states that a fiberwise hyperbolic invariant tori exists given an approximately invariant one that meets the required hypotheses

Linear Precoding performance analysis in a Broadband satellite system with a 2-color dual-polarization reuse scheme

The potential of Joint Multiuser Processing in multi-beam satellite systems is assessed in this paper and proved to be a potential attractive alternative to current systems. The present contribution aims at investigating linear precoding techniques over an accurate multi-beam architecture modeling and system characterization. Power and precoder design problems are approached through well-known linear precoding techniques such as Zero Forcing (ZF) and Regularized-ZF. A dual-polarization 2-color reutilization scheme is considered in combination with precoding techniques. Results show a total throughput improvement of +22% achieved by ZF and +38% considering R-ZF, with respect to a conventional 4-color reuse scheme scenario

Next Generation High Throughput Satellite System

This paper aims at presenting an overview of the state-of-the-art in High Throughput Satellite (HTS) systems for Fixed Satellite Services (FSS) and High Density-FSS. Promising techniques and innovative strategies that can enhance system performance are reviewed and analyzed aiming to show what to expect for next generation ultra-high capacity satellite systems. Potential air interface evolutions, efficient frequency plans,feeder link dimensioning strategies and interference cancellation techniques are presented to show how Terabit/s satellite myth may turn into reality real soon

Etude sur l\u27usage des lecteurs des lecteurs d\u27écran en France et en Francophonie

la Fédération des Aveugles de France, en partenariat avec la société Access42, a mené une enquête par questionnaire portant sur l’usage des lecteurs d’écran en France et en Francophonie. Cette étude permet d’identifier les outils les plus utilisés. Elle permet de guider les choix des bibliothèques souhaitant équiper certains postes informatiques de lecteurs d’écran