{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"id":[{"id":"https:\/\/ror.org\/03mb6wj31","id-type":"ROR","asserted-by":"publisher"},{"id":"https:\/\/www.isni.org\/000000041937028X","id-type":"ISNI","asserted-by":"publisher"},{"id":"https:\/\/www.wikidata.org\/entity\/Q1640731","id-type":"wikidata","asserted-by":"publisher"}],"name":"Universitat Polit\u00e8cnica de Catalunya","acronym":["UPC"]}],"indexed":{"date-parts":[[2026,1,16]],"date-time":"2026-01-16T18:06:04Z","timestamp":1768586764866,"version":"3.49.0"},"reference-count":0,"publisher":"Universitat Polit\u00e8cnica de Catalunya","license":[{"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/es\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>An important issue in today's information society is the security of data transmission against potential intruders, which always put at risk the confidentiality. Current methods to increase security require that the two parties wishing to transmit information, exchange or share one or more security keys. Once the key has been identified, the information can be transferred in a provable secure way using a one-time pad, i. e. the key length is as long as the plaintext. Therefore, the security of the information transmission is based exclusively on the security of the key exchange. Quantum cryptography, or more precisely quantum key distribution (QKD), guarantees absolutely secure key distribution based on the principles of quantum physics, according to which it is not possible to measure or reproduce a state (e.g. polarization or phase of a photon) without being detected. The key is generated out from the measurement of the information encoded into specific quantum states of a photon, named qubits. For example, a qubit can be created using properties such as the polarization or the phase of a photon.\r\n\r\nAchieved goals of this thesis are the development of a new class of high speed integrated photonic sources for applications in quantum key distribution systems, capable of producing unprecedented qubit rates (100 Mbps - 1 Gbps) and transmitting those over larger distances than those achieved so far (&gt;200 km). More specifically the work has been focused on developing faint pulse sources which can be used in very demanding environmental conditions, such as those in Space. For the development of these sources, apart from the optical design, essential is the opto-mechanical engineering as well as the integration with the electronics. One of the objectives was to achieve very high level of integration and power efficiency, e.g. volumes and power consumption between 10 and 100 times smaller than those typical of a laboratory experiment. Moreover, work in related parts of a whole QKD transmission system has been carried out. In particular, a new scheme for a compact, fast and simple random number generator has been demonstrated successfully achieving a random number generation rate of 1.1 Gbps. Also, during the course of this thesis, the development and engineering of a free-space QKD optical link has been initiated. \r\n\r\nThis thesis makes use of novel ideas to alternatively demonstrate proof-of-concept experiments, which could then further develop into commercial products. To this end, close collaborations with world-wide leading companies in the field have been established. The Optoelectronics Group at ICFO has been involved in current European Space Agency (ESA) projects to develop a small footprint and low power consumption quantum transceiver and a high-flux entangled photon source.<\/jats:p>\n                <jats:p>En l\u2019actual societat del coneixement \u00e9s important la seguretat en la transmissi\u00f3 de dades contra potencial intrusos, els quals sempre posen en risc la confidencialitat. M\u00e8todes actuals per incrementar la seguretat requereixen que les dos parts que volen transmetre  informaci\u00f3, intercanvi\u00efn o comparteixin una o m\u00e9s claus. Una vegada la clau ha estat identificada, la informaci\u00f3 pot ser transferida de forma provadament segura utilitzant \u201d\u2018one-time pad\u201d\u2019. Per tant, la seguretat en la transmissi\u00f3 de la informaci\u00f3 es basa exclusivament en la seguretat en l\u2019intercanvi de la clau. La criptografia qu\u00e0ntica, o m\u00e9s precisament distribuci\u00f3 de clau qu\u00e0ntica (QKD), garanteix absolutament la seguretat de la distribuci\u00f3 de la clau basant-se en els principis de la f\u00edsica qu\u00e0ntica, segons la qual no \u00e9s possible mesurar o reproduir un estat (p. e. la polaritzaci\u00f3 o fase d\u2019un fot\u00f3) sense ser detectat. \r\nLa clau es genera a partir de les mesures de la informaci\u00f3 codificada en estat qu\u00e0ntics del fot\u00f3, anomenats qubits. Per exemple, un qubit pot ser creat utilitzant propietats com la polaritzaci\u00f3 o fase d\u2019un fot\u00f3.\r\nEls objectius aconseguits d\u2019aquesta tesis s\u00f3n el desenvolupament d\u2019una nova classe d\u2019emissors fot\u00f2nics d\u2019alta velocitat per a aplicacions en sistemes\r\nde distribuci\u00f3 de clau qu\u00e0ntica, capa\u00e7\u00b8os de produir velocitats de qubit sense precedents (100 Mbps - 1 Gbps) i transmetre\u2019ls a trav\u00e9s de dist\u00e0ncies m\u00e9s llunyanes que les aconseguides fins ara (&gt; 200 Km). M\u00e9s en concret el treball s\u2019ha centrat en el desenvolupament de fonts de pulsos\r\natenuats que poden ser usades en condicions ambientals molt extremes, com les presents a l\u2019Espai. Per al desenvolupament d\u2019aquestes fonts, apart del disseny \u00f2ptic, important\u00edssim es l\u2019enginyeria optomec\u00e0nica com tamb\u00e9 la integraci\u00f3 amb la electr\u00f2nica. Un dels objectius ha estat aconseguir un molt alt nivell de integraci\u00f3 i efici\u00e8ncia de pot\u00e8ncia, p. e. volums i consums de pot\u00e8ncia entre 10 i 100 vegades m\u00e9s petits que els t\u00edpics en experiments de laboratori. Adem\u00e9s, s\u2019ha realitzat treball en altres parts relacionades amb un sistema de transmissi\u00f3 QKD. En particular, un nou esquema per a un generador de n\u00fameros aleatori compacte, r\u00e0pid i simple ha estat positivament demostrat aconseguint velocitats de generaci\u00f3 de n\u00fameros aleatoris de 1:1 Gbps. Tamb\u00e9, el desenvolupament i enginyeria d\u2019un enlla\u00e7 \u00f2ptic per a QKD en espai lliure ha estat iniciat durant aquesta tesis.\r\nAquesta tesis utilitza idees novedoses per a demostrar experiments de prova de concepte, els quals poden esdevenir en productes comercials. Per a aquest fi, s\u2019han establert col\u2022laboracions amb empreses internacionals l\u00edders del sector. A m\u00e9s a m\u00e9s, el Grup d\u2019Optoelectr\u00f2nica de ICFO ha estat involucrat en projectes de la Ag\u00e8ncia Espacial Europea (ESA) per a desenvolupar un transceptor qu\u00e0ntic de tamany redu\u00eft i baix consum de pot\u00e8ncia, el qual tamb\u00e9 cont\u00e9 una font de fotons entrella\u00e7ts d\u2019alt flux.<\/jats:p>","DOI":"10.5821\/dissertation-2117-94926","type":"dissertation","created":{"date-parts":[[2023,10,15]],"date-time":"2023-10-15T01:26:31Z","timestamp":1697333191000},"approved":{"date-parts":[[2013,4,15]]},"source":"Crossref","is-referenced-by-count":0,"title":["Integrated photonic transmitters for secure space quantum communication"],"prefix":"10.5821","author":[{"sequence":"additional","affiliation":[]},{"given":"Marc","family":"Jofre Cruanyes","sequence":"first","affiliation":[]}],"member":"3865","container-title":[],"original-title":[],"deposited":{"date-parts":[[2026,1,16]],"date-time":"2026-01-16T06:45:47Z","timestamp":1768545947000},"score":1,"resource":{"primary":{"URL":"https:\/\/hdl.handle.net\/2117\/94926"}},"subtitle":[],"editor":[{"given":"Valerio","family":"Pruneri","sequence":"first","affiliation":[]}],"short-title":[],"issued":{"date-parts":[[null]]},"references-count":0,"URL":"https:\/\/doi.org\/10.5821\/dissertation-2117-94926","relation":{},"subject":[]}}