Quantum Fourier transform is the building block for creating entanglement

This study demonstrates entanglement can be exclusively constituted by quantum Fourier transform (QFT) blocks. A bridge between entanglement and QFT will allow incorporating a spectral analysis to the already traditional temporal approach of entanglement, which will result in the development of new more performant, and fault-tolerant protocols to be used in quantum computing as well as quantum communication, with particular emphasis in the future quantum Internet

Practical figures of merit and thresholds for entanglement distribution in quantum networks

Before global-scale quantum networks become operational, it is important to consider how to evaluate their performance so that they can be built to achieve the desired performance. We propose two practical figures of merit for the performance of a quantum network: the average connection time and the average largest entanglement cluster size. These quantities are based on the generation of elementary links in a quantum network, which is a crucial initial requirement that must be met before any long-range entanglement distribution can be achieved and is inherently probabilistic with current implementations. We obtain bounds on these figures of merit for a particular class of quantum repeater protocols consisting of repeat-until-success elementary link generation followed by joining measurements at intermediate nodes that extend the entanglement range. Our results lead to requirements on quantum memory coherence times, requirements on repeater chain lengths in order to surpass the repeaterless rate limit, and requirements on other aspects of quantum network implementations. These requirements are based solely on the inherently probabilistic nature of elementary link generation in quantum networks, and they apply to networks with arbitrary topology.Comment: 17 pages, 7 figures. v2: extensively revised and rewritten. Title and abstract modified; added a section on overcoming the repeaterless rate limit; modified statement of Theorem 1. v3: minor changes to match the published versio

Quantum Internet

During my TFG, I investigated the current state of quantum technologies, with a focus on quantum communications and the Quantum Internet. The initial phase includes analyzing the fundamental characteristics of quantum communications, which involves the use of qubits. I mentioned the most advanced deployments of quantum networks to date (QKD networks and entanglement networks). My final study case was based on exploring the potencial of entanglement to improve classical communication capacity. The advantages of Entanglement-Assisted (EA) capacity become evident. Unfortunately, these advantages are significantly reduced when considering an imperfect entanglement distribution. My case study aimed to determine specific ranges and conditions for beneficial classical capacity.Durant el meu TFG, vaig investigar sobre l'estat actual de les tecnologies quàntiques, especialmente en les comunicacions quàntiques i la Internet quàntica. La fase inicial inclou l'anàlisi de les característiques fonamentals de les comunicacions quàntiques, que implica l'ús de qubits. He esmentat els desplegaments més avançats de xarxes quàntiques fins ara (les xarxes QKD i les xarxes d'entrellaçament). El meu cas d'estudi final es va basar en explorar el potencial de l'entrellaçament per millorar la capacitat de comunicació clàssica. Els avantatges de la capacitat assistida per entrellaçament (EA) son evidents. Malauradament, aquests avantatges es redueixen significativament quan es considera una distribució d'entrellaçament imperfecta. El meu estudi de cas tenia com a objectiu determinar els rangs i condicions específics para una capacitat clàssica beneficios