Entanglement Verification in Quantum Networks with Tampered Nodes

In this paper, we consider the problem of entanglement verification across the quantum memories of any two nodes of a quantum network. Its solution can be a means for detecting (albeit not preventing) the presence of intruders that have taken full control of a node, either to make a denial-of-service attack or to reprogram the node. Looking for strategies that only require local operations and classical communication (LOCC), we propose two entanglement verification protocols characterized by increasing robustness and efficiency.Comment: 14 pages, 7 figure

L'effet tunnel assisté par le chaos comme nouvel outil pour la simulation quantique

L'effet tunnel est une manifestation emblématique de la nature ondulatoire de la matière. Il décrit le passage de particules quantiques à travers des barrières de potentiel classiquement infranchissables. Lorsqu'il se produit dans des systèmes dont la dynamique classique est mixte, c'est-à-dire intermédiaire entre chaotique et régulière, l'effet tunnel est un processus bien plus riche que celui présenté dans les livres d'introduction à la mécanique quantique. En effet, dans l'espace des phases classique de ces systèmes, les orbites régulières s'organisent en îlots stables entourés par un mer d'orbites chaotiques instables. L'effet tunnel entre les îlots réguliers est alors partiellement médié par des états ergodiques dans la mer chaotique. Une des signatures emblématiques de cet effet tunnel assisté par le chaos est l'existence de résonances de la fréquence d'oscillation entre deux îlots symétriques. Dans ce manuscrit nous rapportons, en collaboration avec un groupe d'expérimentateurs et expérimentatrice du LCAR à Toulouse, la première observation de ces résonances dans un système quantique, avec une expérience d'atomes froids. Nous présentons également une généralisation de ce mécanisme de transport à des réseaux optiques modulés dans le temps qui forment dans l'espace des phases une chaîne d'îlots d'orbites stables immergés dans une même mer de trajectoires chaotiques. Nous montrons que l'effet tunnel assisté par le chaos s'y traduit par des couplages à longue portée entre les îlots et démontrons que les propriétés de fluctuation statistique de ces couplages sont universelles. De tels couplages à longue portée pourraient servir dans le champ de la simulation quantique pour accéder expérimentalement à de nouvelles classes de systèmes difficiles à réaliser autrement, notamment des systèmes désordonnés critiques. La dernière partie de ce manuscrit est consacrée à l'étude de tels systèmes désordonnés critiques, comme au seuil de la transition d'Anderson, dont les états quantiques sont multifractals : ils sont délocalisés mais non ergodiques et possèdent des fluctuations invariantes d'échelle. Nous caractérisons la dynamique de ces systèmes en décrivant le rôle de la multifractalité sur la diffusion cohérente d'une onde plane. Cette étude est une étape importante vers la caractérisation expérimentale de la multifractalité dans un système quantique, qui reste à ce jour très difficile par d'autres méthodes.Tunneling is an emblematic manifestation of the wave nature of matter. It describes the passage of quantum particles through classically forbidden barriers of energy. When it occurs in systems whose classical dynamics is mixed, that is to say intermediate between chaotic and regular, tunneling is a much richer process than presented in introductory books to quantum mechanics. Indeed, in the classical phase space of such systems, regular orbits organize themselves into stable islands surrounded by a sea of unstable chaotic orbits. Tunneling between regular islands is then partially mediated by ergodic states in the chaotic sea. One of the striking signatures of this chaos-assisted tunneling is the existence of resonances of the oscillation frequency between two neighboring sites. In this thesis we report, in collaboration with an experimental team at LCAR in Toulouse, the first observation of these resonances in a quantum system, with a a cold atom experiment. We also present a generalization of this transport mechanism to driven optical lattices that form in phase space a chain of stable islands surrounded by the same chaotic sea. We show that chaos- assisted tunneling results in very long-range couplings between islands, whose fluctuations statistical propreties are universal. These long-range couplings could be used in the field of quantum simulation to experimentally access new classes of systems, difficult to achieve otherwise, in particular critical disordered systems. The last part of this manuscript is devoted to the study of such critical disordered systems, e.g. at the Anderson transition, whose quantum states are multifractals: they are delocalized but not ergodic and have remarkable scaling properties. We characterize the dynamics of these systems by describing the role of multifractality on the coherent scattering of a plane wave. This study is an important step towards the experimental characterization of multifractality in a quantum system, which remains up to now very difficult by other methods

Multiplexed affinity peptidomic assays: multiplexing and applications for testing protein biomarkers

Biomarkers are increasingly used in a wide range of areas such as sports and clinical diagnostics, biometric applications, forensic analysis and population screening. Testing for such biomarkers requires substantial resources and has traditionally involved centralised laboratory testing. From cancer diagnosis to COVID testing, there is an increasing demand for protein based assays that are portable, easy to use and ideally multiplexed, so that more than one biomarker can be tested at the same time, thus increasing the throughput and reducing time of the analysis and potentially the costs. Events in recent years, not least the ongoing investigations into claims of widespread state-sponsored doping schemes in sport and the COVID-19 pandemic of 2020 highlight the ever-growing requirement and importance of such tests across multiple frontiers. The project evaluated the feasibility of new antipeptide affinity reagents and suitable technologies for application to multiplexed affinity assays geared towards quantitatively analysing a range of analytes. In the first part of this project, key protein biomarkers available from blood serum and covering a range of conditions including cancer, inflammation, and various behavioural traits were chosen from the literature. Peptide antigens for the development of antipeptide polyclonal antibodies for each protein were selected following in silico proteolysis and ranking of the peptides using an algorithm devised as part of this research. A microarray format was used to achieve spatial multiplexing and increase throughput of the assays. The arrays were evaluated experimentally and were tested for their usability for studying up/down regulation of the target biomarkers in human sera samples. Another protein assay format tested for compatibility with affinity peptidomics approach was a gold nanoparticle based lateral flow test. An affinity-based lateral flow test device was built and used for the detection of the benzodiazepine Valium. Here spectral multiplexing of detection was considered. The principle was tested using quantum dot nanoparticles instead of traditionally used gold nanoparticles. The spectral deconvolution was achieved for mixtures containing up to six differently sized quantum dots. In the final part of this project, a search for novel peptide affinity reagents against insulin growth-like factor 1 (IGF-1) was conducted using phage display. Four peptides were identified after screening a phage display library, and the binding of these peptides to IGF-1 was compared to that of traditional antibody

Molecular Imaging

The present book gives an exceptional overview of molecular imaging. Practical approach represents the red thread through the whole book, covering at the same time detailed background information that goes very deep into molecular as well as cellular level. Ideas how molecular imaging will develop in the near future present a special delicacy. This should be of special interest as the contributors are members of leading research groups from all over the world

The role of interfaces in heterostructures: strained manganites and silicon for quantum computing

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 17/09/2013Fac. de Ciencias FísicasTRUEunpu