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Integrated photonics represents a technology that could greatly improve quantum communication networks in terms of cost, size, scaling, and robustness. A key benchmark for this is to demonstrate their performance in complex quantum networking protocols, such as entanglement swapping between truly independent photon-pair sources. Here, using two independent, asynchronously-pumped, integrated Si3N4 microring resonator photon-pair sources, operating in the continuous-wave regime with time-resolved detections, we obtained state of the art Hong-Ou-Mandel (93.2 +/- 1.6%) and entanglement swapping (91.2 +/- 3.4%) visibilities, while maintaining high rates. The time-resolved detection facilitates high spectral purities without the need for spectral filtering. Our results demonstrate the potential of such telecom-band sources for practical, real-world quantum communication.

Metal closo-borates and their derivatives have shown promise in several fields of application from cancer therapy to solid-state electrolytes partly owing to their stability in aqueous solutions and high thermal stability. We report the synthesis and structural analysis of α- and β-CaB10H10, which are structurally and energetically similar, both showing a tetrahedral coordination of Ca2+ to four closo-borate cages. The main distinctions between the α- and β-polymorph are found in the crystal system (monoclinic or orthorhombic), topology (wurtzite or cag), and the degree of displacement of Ca2+ from the center of the coordination tetrahedron. Neutron vibrational spectroscopy measurements further revealed distinct perturbations in the cation-anion interactions arising from the different crystal structures. We also synthesized and structurally investigated five stoichiometric hydrates, CaB10H10·xH2O, x = 1, 4, 5, 6, and 7, and discovered an order-disorder polymorphic transition, α- to β-CaB10H10·6H2O. The hydrates reveal a rich structural diversity with ordered structures, CaB10H10·xH2O, x = 1, 4, 5, 6, and 7, as well as disordered structures, x = 6 and 8. The latter allow for a continuum of compositions within 7-8 molecules of crystal water. The DFT-optimized experimental crystal structures reveal complex networks of three types of hydrogen interactions: dihydrogen bonds, B-Hδ-···+δH-O; hydrogen-hydrogen interactions, B-H···H-B; and hydrogen bonds, O-Hδ+···-δO-H. A rather short B-H···H-B (2.14 Å) interaction is observed for CaB10H10·5H2O, which is locally stabilized by four hydrogen bonds.

One of the most widely discussed features of the cuprate high Tc superconductors is the presence of a pseudogap in the normal state. Recent transport and specific heat measurements have revealed an abrupt transition at the pseudogap critical point, denoted p*, characterized by a drop in carrier density and a strong mass enhancement. In order to give more details about this transition at p*, we performed low-temperature infrared spectroscopy in the normal state of cuprate superconductors La2-xSrxCuO4 (LSCO) and La1.8-xEu0.2SrxCuO4 (Eu-LSCO) for doping contents across the pseudogap critical point p* (from p = 0.12 to 0.24). Through the complex optical conductivity we can extract the spectral weight, K*, of the narrow Drude peak due the coherent motion of the quasi-particles, and the spectral weight enclosed inside the mid-infrared (MIR) band, KMIR, caused by coupling of the quasi-particles to collective excitations of the many-body system. K* is smaller than a third of the value predicted by band calculations, and KMIR forms a dome as a function of doping. We observe a smooth doping dependence of K* through p*, and demonstrate that this is consistent with the observed doping dependence of the carrier density and the mass enhancement. We argue that the superconducting dome is the result of the confluence of two opposite trends, namely the increase of the density of the quasi-particles and the decrease of their coupling to the collective excitations as a function of doping., Comment: 8 pages, 4 figures

Hadron therapy (HT) uses the physical and biological properties of charged particles to treat solid tumors. This thesis aims to contribute to two main HT research topics: the development of affordable beam accelerators complexes and of detector systems allowing the monitoring and control of the delivered dose. Two new linac accelerators for HT of the TERA Foundation are further studied, consolidating the bridge between the accelerators and medical physics worlds. The study includes the development of a 3D simulation software, FLUKA Monte Carlo-based, capable to track particles through the accelerator lines ending in the patient's body and fully predict HT beam characteristics. A new monitoring technique, called fast range verification, was developed and experimentally validated with the aim of verifying the Bragg Peak range for hadron treatments. It is based on Positron Emission Tomography and consists in β+ emitters detection from a short and low-dose pre-irradiation of a tumor part.

Combining climatological insight with state-of-the-art methods in conflict economics, this paper introduces a novel concept in the literature: the impact of the velocity of climate change on riots in Sub-Saharan Africa. Based on a standardized drought index, we build a variable expressing the shifting velocity of climate anomalies. We rely on 4-yearly data at the cell level (0.5°×0.5°), a disaggregation that is tailored to the study of intra-decennial weather trends and locally confined conflicts. We build our empirical strategy from previous results in the conflict literature, which show that negative water shocks (droughts) increase the likelihood of riot occurrence. Our results show that the velocity of drying has a significant amplifying effect on the weather shock - riot relationship. On the contrary, the favorable effects that climatic shifts towards more humid conditions could bring – namely, promoting peace, lose strength in the face of country-wide socio-political and economic drivers. We also find evidence of some, although limited, adaptive capacity in the long run (~ 30 years). Maladaptive strategies are used to cope with climatic duress in the short run (< 4 years). These include regional migrations (

We introduce a dynamic stabilization scheme universally applicable to unidirectional nonlinear coherent waves. By abruptly changing the waveguiding properties, the breathing of wave packets subject to modulation instability can be stabilized as a result of the abrupt expansion a homoclinic orbit and its fall into an elliptic fixed point (center). We apply this concept to the nonlinear Schr\"odinger equation framework and show that an Akhmediev breather envelope, which is at the core of Fermi-Pasta-Ulam-Tsingou recurrence and extreme wave events, can be frozen into a steady periodic (dnoidal) wave by a suitable variation of a single external physical parameter. We experimentally demonstrate this general approach in the particular case of surface gravity water waves propagating in a wave flume with an abrupt bathymetry change. Our results highlight the influence of topography and waveguide properties on the lifetime of nonlinear waves and confirm the possibility to control them., Comment: 6 pages, 3 figures (main text); 8 pages, 8 figures (supplemental material)

Magnesium nuclei in cosmic rays are mainly produced and accelerated in astrophysical sources. While Aluminum nuclei are produced both in astrophysical sources and by the collisions of heavier nuclei with the interstellar medium. Knowledge of the precise behavior of their spectrum are important in understanding the origin, acceleration, and propagation processes of cosmic rays in the Galaxy. The surviving fractions of the radionuclides Be-10 and Al-26 provide information on the cosmic-ray residence time. The surviving fraction of Al-26 can be extracted by the Aluminum-to-Magnesium flux ratio providing information on the energy dependence of the residence time. The precision measurements of Mg and Al fluxes in the rigidity range from 2.15GV to 3.0TV based on data collected by the Alpha Magnetic Spectrometer during its first 8.5 years of operation are presented. A feasibility study of extracting the Be-10 and Al-26 surviving fractions from Be/B and Al/Mg flux ratios is also discussed.

Primordial Black Holes (PBH) can form in the early universe and might comprise a significant fraction of the dark matter. Interestingly, they are accompanied by the generation of Gravitational Wave (GW) signals and they could contribute to the merger events currently observed by the LIGO/Virgo Collaboration (LVC). In this thesis, we study the PBH scenario, addressing various properties at the formation epoch and the computation of abundance beyond the Gaussian paradigm, while also developing the theoretical description of PBH evolution through accretion and mergers, with particular focus on modelling their GW signatures. In a second part, we compare the primordial scenario with current GW data, seizing the possible contribution of PBH binaries to LVC signals and forecasting the potential of future GW detectors, such as Einstein Telescope and LISA, to detect mergers of primordial binaries and the stochastic GW background induced at second order by the PBH formation mechanism., Comment: 256 pages. PhD thesis

Dual-gate tuning on two-dimensional (2D) heterostructures can provide independent control of the carrier concentration and interlayer electrostatic potential, yielding novel electronic and optical properties. In this paper, by utilizing monolayer graphene as both the top gate and a plasmon wavelength magnifier, the optical properties of bilayer graphene (BLG) under dual-gate are quantitatively investigated by nanoinfrared imaging. The hybrid optical modes in the vertically coupled two-layer system are imaged from scattering-type scanning near-field microscopy (s-SNOM). Moreover, plasmon dispersion behaviors under varied dual-gate tuning are explored and explained well with theoretical ones employing tight binding approximation, which reveals the flexibility in individually manipulating the Fermi energy and bandgap. Especially, electron-hole asymmetry in BLG is verified from experiments. Our studies pave route for quantitative near-field investigation of superlattice, topological boundaries, and other emergent phenomena in graphene-based 2D heterostructures.

This thesis focuses on two aspects of the development of quantum memories for quantum communication applications, in two rare earth ion-doped solid state materials. The first part consists in fundamental investigations on Yb:YSO. After a spectroscopy phase, we showed how its anisotropic hyperfine interaction between nuclear and electronic spins enhances the coherence times of both microwave and optical transitions in two different regimes of magnetic field, opening new avenues for a broadband quantum memory with strong microwave coupling. The second part reports on improvements on existing storage protocols in Eu:YSO. A general upgrade of the components of the spin-wave atomic frequency comb protocol led to an improved performance at the single-photon level and to the storage of a time-bin qubit for 20 milliseconds. The same improvements enabled the generation of quantum-correlated pairs of photons delayed by 20 milliseconds, an important step towards quantum repeaters based on the DLCZ protocol.

A highlight of Fermi-liquid phenomenology, as explored in neutral $^3$He, is the observation that in the collisionless regime shear stress propagates as if one is dealing with the transverse phonon of a solid. The existence of this $"$transverse zero sound$"$ requires that the quasiparticle mass enhancement exceeds a critical value. Could such a propagating shear stress also exist in strongly correlated electron systems? Despite some noticeable differences with the neutral case in the Galilean continuum, we arrive at the verdict that transverse zero sound should be generic. We present an experimental setup that should be exquisitely sensitive in this regard: the transmission of terahertz radiation through a thin slab of heavy-fermion material will be strongly enhanced at low temperature and accompanied by giant oscillations, which reflect the interference between light itself and the $"$material photon$"$ being the actual manifestation of transverse zero sound in the charged Fermi liquid., 12 pages, 3 figures

High-dimensional quantum entanglement can give rise to stronger forms of nonlocal correlations compared to qubit systems, offering significant advantages for quantum information processing. Certifying these stronger correlations, however, remains an important challenge, in particular in an experimental setting. Here we theoretically formalise and experimentally demonstrate a notion of genuine high-dimensional quantum steering. We show that high-dimensional entanglement, as quantified by the Schmidt number, can lead to a stronger form of steering, provably impossible to obtain via entanglement in lower dimensions. Exploiting the connection between steering and incompatibility of quantum measurements, we derive simple two-setting steering inequalities, the violation of which guarantees the presence of genuine high-dimensional steering, and hence certifies a lower bound on the Schmidt number in a one-sided device-independent setting. We report the experimental violation of these inequalities using macro-pixel photon-pair entanglement certifying genuine high-dimensional steering. In particular, using an entangled state in dimension $d=31$, our data certifies a minimum Schmidt number of $n=15$., 9 pages, 1 table, 5 figures

We give a pedagogical introduction to the Generalized Hydrodynamic approach to inhomogeneous quenches in integrable many-body quantum systems. We review recent applications of the theory, focusing in particular on two classes of problems: bipartitioning protocols and trap quenches, which represent two prototypical examples of broken translational symmetry in either the system initial state or post-quench Hamiltonian. We report on exact results that have been obtained for generic time-dependent correlation functions and entanglement evolution, and discuss in detail the range of applicability of the theory. Finally, we present some open questions and suggest perspectives on possible future directions., Comment: 46 pages, 13 figures. To appear in JSTAT special issue "Emergent Hydrodynamics in Integrable Many-body Systems"; v2 minor revision. As appears in JSTAT special issue "Emergent Hydrodynamics in Integrable Many-body Systems"

The novel high-temperature polymorph of sodium imidazolate reported in this paper was discovered in the mechanochemical reaction of NaIm with NaBH4 and later prepared directly by thermal treatment of the room-temperature polymorph of NaIm. Solid- state NMR was used for initial elucidation of structural features ; the crystal structure was determined by single-crystal X-ray diffraction, while the in situ HT-XRPD experiments utilizing synchrotron radiation have been performed in order to gain the insight into the structural evolution and thermal stability, in addition to differential thermal analysis and hot-stage microscopy measurements. Contrary to the RT polymorph that forms a dense and hypercoordinated structure without pores, the high-temperature polymorph of NaIm exhibits pores of 50 Å3 that suggest possible application for gas sorption/separation. It is important to highlight that, once formed, the high-temperature polymorph of NaIm retains its structure and remains stable at room temperature.

The important development of quantum technologies during the past decade brought the need for efficient, fast and precise single-photon detection. Superconducting Nanowire Single-Photon Detectors (SNSPDs) are currently considered as the detection method of choice when extreme performances are required. This thesis aimed at investigating this technology, with the objective of improving existing detectors for high-rate applications in quantum communication. This document presents the work and result achieved over four years dedicated to the subject. During this thesis, single-photon detection based on superconducting nanowire has been investigated, with a particular focus on specific requirements for high speed quantum communication applications. The work achieved ranges from the design and nano-fabrication of the structures, to the characterization and the understanding of the physics, detection models and fundamental limits of the devices.

In this work we develop nonlinear models to study the propagation of surface water waves.The Nonlinear Schrödinger Equation (NLSE) is used to describe the evolution of the envelope of a wave packet. However, the NLSE, an equation obtained at third order in steepness in the multiscale expansion, is symmetric in time. Therefore it is unable to reproduce the asymmetric development of the water waves envelope. We then propose four models obtained at fourth order in steepness to recover asymmetry and improve the agreement with experiments. Those four models are adapted from the fourth-order NLSE found in the literature. With those models, we perform numerical simulations of the envelope propagation in space. We simulate the water waves as propagating in one direction along a wave tank of constant depth. This simulation is performed with the third-order NLSE and the four fourth-order models for different physical parameters (water depth, carrier wave frequency, steepness of the wave). We then study the impact of the modified fourth-order models on the envelope propagation and we carefully investigate the role of each term in such model equations. On the other hand we compare our simulations with real measurement in the wave flume of the University of Sydney. We then analyse the agreement between our models and the experiment.

We present a collision model for the charging of a quantum battery by identical nonequilibrium qubit units. When the units are prepared in a mixture of energy eigenstates, the energy gain in the battery can be described by a classical random walk, where both average energy and variance grow linearly with time. Conversely, when the qubits contain quantum coherence, interference effects buildup in the battery and lead to a faster spreading of the energy distribution, reminiscent of a quantum random walk. This can be exploited for faster and more efficient charging of a battery initialized in the ground state. Specifically, we show that coherent protocols can yield higher charging power than any possible incoherent strategy, demonstrating a quantum speed-up at the level of a single battery. Finally, we characterize the amount of extractable work from the battery through the notion of ergotropy., Comment: 4 pages, 5 figures

Increasingly sophisticated quantum computers motivate the exploration of their abilities in certifying genuine quantum phenomena. Here, we demonstrate the power of state-of-the-art IBM quantum computers in correlation experiments inspired by quantum networks. Our experiments feature up to 12 qubits and require the implementation of paradigmatic Bell-State Measurements for scalable entanglement-swapping. First, we demonstrate quantum correlations that defy classical models in up to nine-qubit systems while only assuming that the quantum computer operates on qubits. Harvesting these quantum advantages, we are able to certify 82 basis elements as entangled in a 512-outcome measurement. Then, we relax the qubit assumption and consider quantum nonlocality in a scenario with multiple independent entangled states arranged in a star configuration. We report quantum violations of source-independent Bell inequalities for up to ten qubits. Our results demonstrate the ability of quantum computers to outperform classical limitations and certify scalable entangled measurements., npj Quantum Information, 7 (1), ISSN:2056-6387

Central America is one of the regions that is most vulnerable to hydrometeorological events and social conflicts. Recently, drought events have become more frequent and are exacerbating pre-existing factors that drive social conflicts. This study focuses on the spatio-temporal relationship between unusually dry conditions and social conflicts in Central America. To describe this relationship, I developed a long-term (1990-2015) monthly panel dataset at the geographic cell level (0.5 x 0.5 degrees). The results do not show a statistically significant relationship between negative water balances (unusually dry conditions) and social conflicts in general. Nevertheless, there is some evidence that suggests that the risk of social conflicts increases when unusually dry conditions occur in locations characterized by limited water supply.

High-performance Nb3Sn superconducting wires have become one of the key technologies for the development of next generation accelerator magnets. While their large critical current densities enable the design of compact accelerator-quality magnets for their operation above 10 T, the noticeable reduction of the conductor performance due to mechanical strain appears as a new essential characteristic in magnet design. In this work, we extensively investigate the effect of transverse loads, up to 250 MPa, in state-of-the-art Nb3Sn Restacked-Rod-Process round superconducting wires. The tests are performed using a compressive Walters spring device, where the force is applied to the resin-impregnated wire, and the critical current is measured under magnetic fields ranging from 16 to 19 T. As a complement, critical current measurements under axial strain are also performed using a standard Walters spring. Interestingly, the study shows that the wire’s electro-mechanical response under transverse stress depends on the initial axial strain condition. Nonetheless, when the main direction load becomes predominant, all tested wires converge to a common behavior. This observation allowed us to combine the results from critical current measurements under the loads exerted in both directions (axial and transverse), shedding some new light on the mechanisms behind critical current degradation.

All full-fledged theories in physics boil down to the study of operator equations. They are encompassing differential equations (e.g. equations of motion) that involve operators acting on infinite-dimensional spaces of functions such as Hilbert spaces. From the point of view of spectral theory, it amounts to the eigendecomposition of said operator. In this work, we focus on Schrödinger type spectral problems. For their own sake, but also because they connect to more complicated quantum theories through dualities e.g. supersymmetric Yang-Mills or, via the TS/ST correspondence, topological strings on Calabi-Yau threefolds. The main tool we use in order to extract exact results are exact quantization conditions, functional relations that fully encode the spectrum of a given operator. We explore Hermitian as well as non-Hermitian (resonant) spectral problems through semiclassical WKB analysis, resurgence, dualities, and integral TBA equations, focusing on concrete examples. We develop a method for computing traces of arbitrary functions of an operator exactly.

Cosmic rays are charged particles originating from the cosmos, the sources, acceleration mechanism and propagation of which are of great interests to the studies in astrophysics. Cosmic-ray beryllium is the lightest pure secondary nuclei, produced by spallation of heavier cosmic-ray nuclei during their propagation in the interstellar medium and therefore carrying important information on this process. Particularly, 10Be has a half-life comparable with the time for cosmic rays to escape from the confinement of the Galaxy. The precision measurements of beryllium isotopes provide unique opportunities to probe propagation models. In this thesis, the measurement of the beryllium isotopic fluxes, from 0.51 GeV/n to 11.2 GeV/n, and the updated measurement of the cosmic-ray beryllium total flux, from 1.92 GV to 3.3 TV, based on events collected by the Alpha Magnetic Spectrometer during its first 8.5 years of operations on the International Space Station are presented.

As the heaviest particle of the Standard Model, the top quark is a key ingredient in both precision electroweak physics measurements and searches for new physics models. In this thesis are presented single- and double-differential cross-section measurements for the production of top-quark pairs in the resolved topology of the all-hadronic channel, using data collected by the ATLAS detector at the CERN LHC. Future prospects for the application of machine learning algorithms for the reconstruction of the ttbar all-hadronic system are also presented and validated. This thesis also includes work related to the upgrade program of the ATLAS trigger and data acquisition system for the High-Luminosity LHC. In particular, studies for the development of the hardware tracking for the trigger are presented.

Phase transitions and their accompanying concepts of criticality and universality are a foundation stone of statistical physics. Gapped spin-dimer systems are an ideal testbed to study criticality because a quantum phase transition can be induced by a magnetic field resulting in a phase equivalent to the XY spin model. It was proposed that BaCuSi2O6, a quasi-2D spin-dimer system consisting of stacked bilayers, undergoes a dimensional reduction, from 3D to 2D, thereby realizing an effective 2D-XY spin model. In this thesis, we investigate the magnetic excitations and order in BaCuSi2O6 and Ba0.9Sr0.1CuSi2O6 using a combination of experimental techniques and analyze the collected data by modern statistical methods. We find that BaCuSi2O6 contains three different bilayer types, which cause an anomalous scaling regime previously misinterpreted as dimensional reduction. Furthermore, we verify that the bilayers in Ba0.9Sr0.1CuSi2O6 are equivalent and that this system therefore displays 3D scaling without any hallmarks of 2D physics.

The Large Hadron Collider (LHC) uses proton-proton collisions to probe the fundamental building blocks of matter. Each collision produces thousands of particles scattering away from the detector center at nearly the speed of light. Reconstructing the trajectories of particles is a crucial task in most physics analysis. However, due to the rise in the number of simultaneous proton-proton interactions at the High Luminosity LHC (HL-LHC), the current tracking techniques will be the dominant component in CPU requirements. This thesis proposes the extension of existing as well as the design of novel Machine Learning (ML) approaches for the tracking of particles in the ATLAS experiment. We propose to describe and extend the similarity search problem in particle tracking through Approximate Nearest Neighbors (ANNs). In this context, the distance between data points is redefined with a tracking aware metric learning model termed TrackNet. Additionally, ANNs and metric learning models are evaluated on the TrackML dataset and on the ATLAS Inner Tracker Phase II dataset. We propose the Dynamic Tracking Linkage (DTL) clustering algorithm to process the output of the TrackNet model and to retrieve the final particle trajectories. This tracking inspired algorithm encapsulates physics constraints in its pairwise distance as well as a trained classifier that acts as an automatic stopping criteria.

Reliable and precise measurements of the relative energy of band edges in semiconductors are needed to determine band gaps and band offsets, as well as to establish the band diagram of devices and heterostructures. These measurements are particularly important in the field of two-dimensional materials, in which many new semiconducting systems are becoming available through exfoliation of bulk crystals. For two-dimensional semiconductors, however, commonly employed techniques suffer from difficulties rooted either in the physics of these systems, or of technical nature. The very large exciton binding energy, for instance, prevents the band gap to be determined from a simple spectral analysis of photoluminescence, and the limited lateral size of atomically thin crystals makes the use of conventional scanning tunneling spectroscopy cumbersome. Ionic gate spectroscopy is a newly developed technique that exploits ionic gate field-effect transistors to determine quantitatively the relative alignment of band edges of two-dimensional semiconductors in a straightforward way, directly from transport measurements (i.e., from the transistor electrical characteristics). The technique relies on the extremely large geometrical capacitance of ionic gated devices that -- under suitable conditions -- enables a change in gate voltage to be directly related to a shift in chemical potential. Here we present an overview of ionic gate spectroscopy, and illustrate its relevance with applications to different two-dimensional semiconducting transition metal dichalcogenides and van der Waals heterostructures.

In the presence of multiple bands, well-known electronic instabilities may acquire new complexity. While multiband superconductivity is the subject of extensive studies, the possibility of multiband charge density waves (CDWs) has been largely ignored so far. Here, combining energy dependent scanning tunnelling microscopy (STM) topography with a simple model of the charge modulations and a self-consistent calculation of the CDW gap, we find evidence for a multiband CDW in 2H-NbSe2. This CDW not only involves the opening of a gap on the inner band around the K-point, but also on the outer band. This leads to spatially out-of-phase charge modulations from electrons on these two bands, which we detect through a characteristic energy dependence of the CDW contrast in STM images., While multiband superconductivity is the subject of extensive studies, the possibility of multiband charge density waves (CDW) remains elusive. Here, the authors report evidence of gap opening on both inner and outer bands by a CDW state in 2H-NbSe2, suggesting a possible multiband CDW.

We study the quantum quench in two coupled Tomonaga-Luttinger Liquids (TLLs), from the off-critical to the critical regime, relying on the conformal field theory approach and the known solutions for single TLLs. We consider a squeezed form of the initial state, whose low energy limit is fixed in a way to describe a massive and a massless mode, and we encode the non-equilibrium dynamics in a proper rescaling of the time. In this way, we compute several correlation functions, which at leading order factorize into multipoint functions evaluated at different times for the two modes. Depending on the observable, the contribution from the massive or from the massless mode can be the dominant one, giving rise to exponential or power-law decay in time, respectively. Our results find a direct application in all the quench problems where, in the scaling limit, there are two independent massless fields: these include the Hubbard model, the Gaudin-Yang gas, and tunnel-coupled tubes in cold atoms experiments., Comment: New section with goal and main results included (1.1), further changes and explanations in sections 2 and 4

SUMMARYTubulin dimers assemble into dynamic microtubules which are used by molecular motors as tracks for intracellular transport. Organization and dynamics of the microtubule network is commonly thought to be regulated at the polymer ends, where tubulin-dimers can be added or removed. Here we show that molecular motors running on microtubules cause exchange of dimers along the shaft. These sites of dimer exchange act as rescue sites where depolymerising microtubules stop shrinking and start re-growing. Consequently, the average length of microtubules increases depending on how frequently they are used as motor tracks. An increase of motor activity densifies the cellular microtubule network and enhances cell polarity. Running motors leave marks in the shaft serving as traces of microtubule usage to organize the polarity landscape of the cell.

The coherence of an individual quantum state can be meaningfully discussed only when referring to a preferred basis. This arbitrariness can however be lifted when considering sets of quantum states. Here we introduce the concept of set coherence for characterising the coherence of a set of quantum systems in a basis-independent way. We construct measures for quantifying set coherence of sets of quantum states as well as quantum measurements. These measures feature an operational meaning in terms of discrimination games and capture precisely the advantage offered by a given set over incoherent ones. Along the way, we also connect the notion of set coherence to various resource-theoretic approaches recently developed for quantum systems., 10 pages

Frustrated magnetism is a frontier theme of modern condensed matter research. The presence of competing interactions in frustrated systems lead to the emergence of highly degenerate ground states. The frustrated magnetism is prevalent in the diverse class of materials and offers an extremely fertile ground to discover novel states such as spin ice, spin liquid, skyrmions etc. The work presented in this thesis is essentially devoted to three different magnetically frustrated systems, which advances our understanding of matter and materials and also push important developments of experimental and theoretical methods. The investigation of magnetic frustration in the three different systems involves the pyrochlore lattice CdYb2Se4, the diamond lattice MnSc2X4 (X=S, Se), and the triangular lattice MGa2S4 (M=Fe, Ni) using neutron scattering as the principal probe.

Studying the collective excitations in charge neutral graphene (CNG) has recently attracted a great interest because of unusual mechanisms of the charge carrier dynamics. The latter can play a crucial role for formation of recently observed in twisted bilayer CNG graphene plasmon polaritons (GPPs) associated with the interband transitions between the flat electronic bands. Besides, GPPs in CNG can be a tool providing insights into various quantum phenomena in CNG via optical experiments. However, the properties of interband GPPs in CNG are not known, even in the simplest configurations. Here, we show that magnetically-biased single-layer CNG can support interband GPPs of both transverse magnetic and transverse electric polarizations (particularly, at zero temperature). GPPs exist inside the absorption bands originating from the electronic transitions between Landau levels and are tunable by the magnetic field. We place our study into the context of potential near-field and far-field optical experiments., We acknowledge funding from Spain’s MINECO under Grant No. MAT2017-88358-C3 and funding from the European Union Seventh Framework Programme under grant agreement no. 881603 Graphene Flagship for Core 3 . L.M.M. acknowledge Aragon Government through project Q-MAD. A.Y.N. acknowledges the Basque Department of Education (grant numbers PIBA-2020-1-0014). The research for A.B.K. was supported by the Swiss National Science Foundation.

We uncover a new family of few-body topological phases in periodically driven fermionic systems in two dimensions. These phases, which we term correlation-induced anomalous Floquet insulators (CIAFIs), are characterized by quantized contributions to the bulk magnetization from multi-particle correlations, and are classified by a family of integer-valued topological invariants. The CIAFI phases do not require many-body localization, but arise in the generic situation of k-particle localization, where the system is localized (due to disorder) for any finite number of particles up to a maximum number, k. We moreover show that, when fully many-body localized, periodically driven systems of interacting fermions in two dimensions are characterized by a quantized magnetization in the bulk, thus confirming the quantization of magnetization of the anomalous Floquet insulator. We demonstrate our results with numerical simulations.

International audience; Precise knowledge of the charge and rigidity dependence of the secondary cosmic ray fluxes and the secondary-to-primary flux ratios is essential in the understanding of cosmic ray propagation. We report the properties of heavy secondary cosmic ray fluorine F in the rigidity $R$ range 2.15 GV to 2.9 TV based on 0.29 million events collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The fluorine spectrum deviates from a single power law above 200 GV. The heavier secondary-to-primary F/Si flux ratio rigidity dependence is distinctly different from the lighter B/O (or B/C) rigidity dependence. In particular, above 10 GV, the $^{\textrm{F/Si}}_{\textrm{B/O}}$ ratio can be described by a power law $R^δ$ with $δ=0.052±0.007$. This shows that the propagation properties of heavy cosmic rays, from F to Si, are different from those of light cosmic rays, from He to O, and that the secondary cosmic rays have two classes.

At ambient pressure, lithium molybdenum purple bronze (Li0.9Mo6O17) is a quasi-one dimensionalsolid in which the anisotropic crystal structure and the linear dispersion of the underlying bandsproduced by electronic correlations possibly bring about a rare experimental realization of Tomomaga-Luttinger liquid physics. It is also the sole member of the broader purple molybdenum bronzes familywhere a Peierls instability has not been identified at low temperatures. The present study reports apressure-induced series of phase transitions between 0 and 12 GPa. These transitions are stronglyreflected in infrared spectroscopy, Raman spectroscopy, and x-ray diffraction. The most dramaticeffect seen in optical conductivity is the metalization of thec-axis, concomitant to the decrease ofconductivity along theb-axis. This indicates that high pressure drives the material away from itsquasi-one dimensional behavior at ambient pressure. While the first pressure-induced structure ofthe series is resolved, the identification of the underlying mechanisms driving the dimensional changein the physics remains a challenge.

We consider the question of characterising the incompatibility of sets of high-dimensional quantum measurements. We introduce the concept of measurement incompatibility in subspaces. That is, starting from a set of measurements that is incompatible, one considers the set of measurements obtained by projection onto any strict subspace of fixed dimension. We identify three possible forms of incompatibility in subspaces: (i) incompressible incompatibility: measurements that become compatible in every subspace, (ii) fully compressible incompatibility: measurements that remain incompatible in every subspace, and (iii) partly compressible incompatibility: measurements that are compatible in some subspace and incompatible in another. For each class we discuss explicit examples. Finally, we present some applications of these ideas. First we show that joint measurability and coexistence are two inequivalent notions of incompatibility in the simplest case of qubit systems. Second we highlight the implications of our results for tests of quantum steering., Comment: 12 pages, no figures, comments are welcome! v2: published version

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed and an upper limit of $0.60 \times 10^{-2}$ is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV., 5 pages, 4 figures

Since its first demonstration, Laser Induced Aerosol Formation (LIAF) was studied in various environmental conditions and laser parameters. LIAF driven by UV and near-IR lasers mainly relies on the nitrogen photo-oxidative chemistry, leading to the production of hygroscopic HNO3, which stabilizes the growth of aerosol nanoparticles. Mid-IR lasers were expected to be drastically less effective for LIAF, due to their much lower multiphoton photodissociation and ionization rates. Here we report on the observation of surprisingly high yields of nano-metric and sub-µm aerosol formation driven by mid-IR laser pulses, which cannot be explained by the HNO3-pathway. We hereby evidence a new mechanism of aerosol stabilization and growth, based on the resonant excitation of volatile organic compounds (VOCs) by mid-IR pulses whose spectrum is broadened during filamentation.

International audience; The electro-mechanical and electro-thermal properties of high-performance Restacked-Rod-Process (RRP) Nb$_{3}$Sn wires are key factors in the realization of compact magnets above 15 T for the future particle physics experiments. Combining X-ray micro-tomography with unsupervised machine learning algorithm, we provide a new tool capable to study the internal features of RRP wires and unlock different approaches to enhance their performances. Such tool is ideal to characterize the distribution and morphology of the voids that are generated during the heat treatment necessary to form the Nb$_{3}$Sn superconducting phase. Two different types of voids can be detected in this type of wires: one inside the copper matrix and the other inside the Nb$_{3}$Sn sub-elements. The former type can be related to Sn leaking from sub-elements to the copper matrix which leads to poor electro-thermal stability of the whole wire. The second type is detrimental for the electro-mechanical performance of the wires as superconducting wires experience large electromagnetic stresses in high field and high current conditions. We analyze these aspects thoroughly and discuss the potential of the X-ray tomography analysis tool to help modeling and predicting electro-mechanical and electro-thermal behavior of RRP wires and optimize their design.

We report the evolution of the lattice, electronic and magnetic structure of nickelates along the series using various optical spectroscopy techniques. The crystal structures from the highest to the lowest symmetry present in the phase diagram, the electronic structure and the different probable magnetic orders below the Neel temperature are described in detail. A general introduction on optical and Raman spectroscopies as well as descriptions of different optical measurement techniques are also presented. We show the optical properties of LaNiO3 films tuned from compressive to tensile strain, which shows an evolution of free carrier spectral weight and mass enhancement as a function of strain. We report the Raman spectroscopic evidence for multiferroicity in rare earth nickelate single crystals (R=Y, Er, Ho, Dy, Sm and Nd), which shows the appearance of new optical modes below the Neel temperature. We show also the impact of pressure on SmNiO3 and NdNiO3 single crystals.

This thesis investigates two important subjects in cosmology: the 2-point functions of the galaxy number counts, and the vorticity field of matter. In the first four chapters, we make a general treatment of the galaxy number counts, and discuss contributions to it using perturbation theory. These results are then used to construct the fully relativistic correlation function, which is valid beyond the flat-sky approximation. A publicly available code is provided for a fast and accurate numerical evaluation of the 2-point function and its multipoles, which allows us to make accurate and precise predictions on cosmological parameters from future and planned experiments. Lastly, we study the mechanism responsible for the fact that galaxies rotate, the vorticity field of matter, using numerical methods.

We study the quench dynamics in free fermionic systems in the prototypical bipartitioning protocol obtained by joining two semi-infinite subsystems prepared in different states, aiming at understanding the interplay between quantum coherences in space in the initial state and transport properties. Our findings reveal that, under reasonable assumptions, the more correlated the initial state, the slower the transport is. Such statement is first discussed at qualitative level, and then made quantitative by introducing proper measures of correlations and transport ``speed''. Moreover, it is supported for fermions on a lattice by an exact solution starting from specific initial conditions, and in the continuous case by the explicit solution for a wider class of physically relevant initial states. In particular, for this class of states, we identify a function, that we dub \emph{transition map}, which takes the value of the stationary current as input and gives the value of correlation as output, in a protocol-independent way. As an aside technical result, in the discrete case, we give an expression of the full counting statistics in terms of a continuous kernel for a general correlated domain wall initial state, thus extending the recent results in [Moriya, Nagao and Sasamoto, JSTAT 2019(6):063105] on the one-dimensional XX spin chain., Comment: 35 pages, 10 figures

The Quantum Symmetric Simple Exclusion Process (Q-SSEP) is a model for quantum stochastic dynamics of fermions hopping along the edges of a graph with Brownian noisy amplitudes and driven out-of-equilibrium by injection-extraction processes at a few vertices. We present a solution for the invariant probability measure of the one dimensional Q-SSEP in the infinite size limit by constructing the steady correlation functions of the system density matrix and quantum expectation values. These correlation functions code for a rich structure of fluctuating quantum correlations and coherences. Although our construction does not rely on the standard techniques from the theory of integrable systems, it is based on a remarkable interplay between the permutation groups and polynomials. We incidentally point out a possible combinatorial interpretation of the Q-SSEP correlation functions via a surprising connexion with geometric combinatorics and the associahedron polytopes., 46 pages, 3 figures

Although complex numbers are essential in mathematics, they are not needed to describe physical experiments, as those are expressed in terms of probabilities, hence real numbers. Physics, however, aims to explain, rather than describe, experiments through theories. Although most theories of physics are based on real numbers, quantum theory was the first to be formulated in terms of operators acting on complex Hilbert spaces1,2. This has puzzled countless physicists, including the fathers of the theory, for whom a real version of quantum theory, in terms of real operators, seemed much more natural3. In fact, previous studies have shown that such a ‘real quantum theory’ can reproduce the outcomes of any multipartite experiment, as long as the parts share arbitrary real quantum states4. Here we investigate whether complex numbers are actually needed in the quantum formalism. We show this to be case by proving that real and complex Hilbert-space formulations of quantum theory make different predictions in network scenarios comprising independent states and measurements. This allows us to devise a Bell-like experiment, the successful realization of which would disprove real quantum theory, in the same way as standard Bell experiments disproved local physics., A Bell-like experiment that discriminates between real-number and complex-number multipartite quantum systems could disprove real quantum theory.

Le paratonnerre laser est une idée ralliant à la fois la technologie de pointe des lasers de forte puissance et la volonté humaine de se protéger contre la foudre et d'ainsi dompter ce phénomène de la nature. Poursuivie depuis près de quarante ans, la recherche sur les paratonnerre lasers est restée en retrait depuis presque quinze ans maintenant. L'évolution des lasers ultra-intenses et de fortes puissance moyenne en revanche voit l'émergence de nouvelle perspectives en la matière. Ce travail rapporte les efforts au sein du projet européen ”Laser Lightning Rod” afin de réaliser une nouvelle expérience de paratonnerre laser en utilisant la technologie, nouvellement accessible, des lasers ultra-intenses haute puissance moyenne, haute puissance crête. Différents aspects de la propagation à longue distance de filaments et la physique de l'interaction laser-décharges avec différentes stratégies telles la conversion en fréquence sont étudiées ici. Les aspects logistiques, ainsi que la physique évoluant autour de la réalisation d'un tel projet sont abordés.

Protecting secrets is a key challenge in our contemporary information-based era. In common situations, however, revealing secrets appears unavoidable, for instance, when identifying oneself in a bank to retrieve money. In turn, this may have highly undesirable consequences in the unlikely, yet not unrealistic, case where the bank's security gets compromised. This naturally raises the question of whether disclosing secrets is fundamentally necessary for identifying oneself, or more generally for proving a statement to be correct. Developments in computer science provide an elegant solution via the concept of zero-knowledge proofs: a prover can convince a verifier of the validity of a certain statement without facilitating the elaboration of a proof at all. In this work, we report the experimental realisation of such a zero-knowledge protocol involving two separated verifier-prover pairs. Security is enforced via the physical principle of special relativity, and no computational assumption (such as the existence of one-way functions) is required. Our implementation exclusively relies on off-the-shelf equipment and works at both short (60 m) and long distances ($\geqslant$400 m) in about one second. This demonstrates the practical potential of multi-prover zero-knowledge protocols, promising for identification tasks and blockchain applications such as cryptocurrencies or smart contracts., 8 pages, 3 figures