Generador quàntic de nombres aleatoris per a aplicacions industrials

Carles Abellán Sánchez

Valeri Pruneri

Randomness is one of the most intriguing, inspiring and debated topics throughout history. It is a concept that arises when we ask ourselves about our own existence: Why are we the way we are? Do we have free will? Is evolution the result of chance? And at the same time, when we try to understand our relationship with the universe itself. Why are we here? When or how did it all begin? Is the universe a deterministic machine or is there room for chance? Surprisingly, randomness also plays a crucial role in the information and technology era. Random numbers are used in communication protocols such as Ethernet, in classification and processing algorithms such as Page Rank. It is also used in Monte Carlo methods, within the fields of physics, biology, chemistry, finance or mathematics. But the most iconic application for random numbers is found in the field of cryptography or cybersecurity where random numbers generate cryptographic keys, the basic element that provides the security and privacy of our communications. The thesis starts from the following fundamental question: Does randomness exist in photonics? If so, how can we extract it and make it accessible to everyone? To address these two questions, tools from fundamental physics to engineering have been combined. The thesis starts from a detailed study of the phase diffusion process in semiconductor lasers and how to apply this process to the generation of random numbers. Unlike other physical processes based on deterministic laws of nature, phase diffusion has a purely quantum origin, and therefore, is an ideal source for generating random numbers. First, and using this phase diffusion process, we created the fastest quantum random number generator ever implemented (at that time) using only components from the telecommunications industry. More than 40 Gb/s were demonstrated using a pulsed laser scheme. Subsequently, we built several prototypes that were tested in fundamental science and supercomputing applications. In particular, some of the prototypes developed in this thesis were key in the famous loophole-free Bell tests experiments performed in 2015. In the process of building these prototypes, we started a new line of research to try to answer a new question: How do we know if the random numbers we generate really arise from the phase diffusion process? As a result, we introduced a new methodology, randomness metrology. Finally, we moved in the direction of miniaturization of the technology using techniques from the integrated photonics industry. In particular, we demonstrated the first fully integrated quantum random number generator, using a two-laser scheme on an Indium Phosphide chip. In parallel, we also demonstrated the integration of part of the device using Silicon technology, thus opening the door to large-scale production through the most advanced semiconductor industry.

En una societat impregnada per les tecnologies de la informació i la comunicació, garantir la seguretat de les dades és de vital importància. Des de l'intercanvi de missatges amb els nostres amics fins a permetre que les empreses i els governs comparteixin dades sensibles, la seguretat també és de vital importància en el desenvolupament de la societat hiperconnectada. En aquest nou paradigma tecnològic, milers de milions de dispositius de la Internet de les Coses es connectaran a Internet, juntament amb dispositius portàtils i sistemes d'atenció mèdica personalitzats. Els cotxes autònoms ens portaran a tot arreu, i les tecnologies de la Indústria 4.0 i la cadena de blocs transformaran les empreses i les operacions a tot el món. Tanmateix, sense garanties de seguretat efectives i a llarg termini, la majoria d'aquestes noves tecnologies no arribaran mai al mercat. Les tecnologies actuals de ciberseguretat es basen en suposicions computacionals no provades, cosa que compromet la privadesa de les nostres comunicacions. Les conseqüències de tenir totes les nostres dades exposades són incommensurables, i hi ha una urgència per desenvolupar noves solucions a llarg termini. Sorprenentment, les tecnologies quàntiques ofereixen oportunitats úniques per a aquest esforç. Les fonts d'entropia quàntica i els sistemes de distribució de claus quàntiques poden resoldre dos dels requisits més bàsics de la criptografia: la generació de claus impredictibles i la seva distribució. En aquesta tesi, hem desenvolupat i demostrat una font d'entropia quàntica altament escalable amb el potencial de ser integrada en qualsevol dispositiu connectat, proporcionant en última instància garanties de seguretat sense precedents en qualsevol dispositiu. La mateixa tecnologia per assegurar les comunicacions també es pot utilitzar en algoritmes aleatoris, que s'utilitzen per resoldre problemes complexos, com ara en mètodes de Monte Carlo per a finances, ciència o enginyeria, i en l'aprenentatge automàtic per a la intel·ligència artificial.

Randomness; Existence; Free Will; Evolution; Chance; Universe; Deterministic Machine; Information and Technology Era; Random Numbers; Communication Protocols; Ethernet; Classification Algorithms; Processing Algorithms; Page Rank; Monte Carlo Methods; Physics; Biology; Chemistry; Finance; Mathematics; Cryptography; Cybersecurity; Cryptographic Keys; Security; Privacy; Photonics; Phase Diffusion Process; Semiconductor Lasers; Quantum Origin; Quantum Random Number Generator; Telecommunications Industry; Pulsed Laser Scheme; Prototypes; Fundamental Science; Supercomputing Applications; Loophole-free Bell Tests; Randomness Metrology; Miniaturization; Integrated Photonics Industry; Fully Integrated Quantum Random Number Generator; Two-Laser Scheme; Indium Phosphide Chip; Silicon Technology; Large-Scale Production; Semiconductor Industry.