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Place, stratégies de placement et tactiques de positionnement en linguistique
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La parole intérieure entre théorie et pratique dans Mes Nippes de Gabriel Bergounioux
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Jeux humoristiques avec les délires de la surinterprétation et du surinvestissement affectif (Moi et François Mitterrand d’H. Le Tellier)
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Optimal Fidelity Estimation from Binary Measurements for Discrete and Continuous Variable Systems
No full text40 pages main text, 4 pages of appendicesInternational audienceEstimating the fidelity between a desired target quantum state and an actual prepared state is essential for assessing the success of experiments. For pure target states, we use functional representations that can be measured directly and determine the number of copies of the prepared state needed for fidelity estimation. In continuous variable (CV) systems, we utilise the Wigner function, which can be measured via displaced parity measurements. We provide upper and lower bounds on the sample complexity required for fidelity estimation, considering the worst-case scenario across all possible prepared states. For target states of particular interest, such as Fock and Gaussian states, we find that this sample complexity is characterised by the -norm of the Wigner function, a measure of Wigner negativity widely studied in the literature, in particular in resource theories of quantum computation. For discrete variable systems consisting of qubits, we explore fidelity estimation protocols using Pauli string measurements. Similarly to the CV approach, the sample complexity is shown to be characterised by the -norm of the characteristic function of the target state for both Haar random states and stabiliser states. Furthermore, in a general black box model, we prove that, for any target state, the optimal sample complexity for fidelity estimation is characterised by the smoothed -norm of the target state. To the best of our knowledge, this is the first time the -norm of the Wigner function provides a lower bound on the cost of some information processing task
La cécité comme atout et les arts : des arts aveugles aux études critiques de cécité et retour
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Georg Forster: Perfectibilité et critique interne des civilisations européennes
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Refining the evaluation of speech synthesis: A summary of the Blizzard Challenge 2023
No full textInternational audienceThe Blizzard Challenge has benchmarked progress in Text-to-Speech (TTS) since 2005. The Challenge has seen important milestones passed, with results suggesting that synthetic speech was indistinguishable from natural speech in terms of intelligibility in 2021 and that by that same year it was perhaps even indistinguishable in naturalness. The high quality of synthetic speech generated by the latest TTS systems has thus revealed limitations with ITU-T P.800.1 Mean Opinion Score (MOS) in detecting the remaining differences between synthetic and natural speech. Yet, it was the only method used in previous Challenges and is still the most popular method in the field for speech synthesis evaluation. In the 2023 Challenge, we addressed observed limitations of past Challenges by incorporating state-of-the-art speech synthesis evaluation techniques to refine the evaluation of speech quality, speaker similarity and intelligibility. For speech quality, a relative comparison of the systems receiving the best MOS was able to discover a greater number of significant differences between systems. Regarding speaker similarity, we demonstrated that there is a strong bias depending on whether the listeners are familiar with the target voice or not. As for intelligibility, the evaluation of language-specific phenomena, such as the pronunciation of homographs, better highlighted system limits compared to global transcription tasks of synthesised utterances. In addition to reporting results for the 18 entries to the 2023 Challenge, we extend the results analysis to type of TTS module to provide some insights on the most recent advances in model design. Overall, this year's results demonstrate the need for a shift towards new methods for refining TTS evaluation to shed light on increasingly smaller and localised differences between synthesised and natural speech
Milieux, histoire(s) et terroirs de Plinthine et de Taposiris Magna : facteurs et enjeux socio-environnementaux de l’implantation des sites et de l’exploitation de leur environs immédiats
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Vanadium isotope fractionation during early planetary evolution: Insights from achondrite analyses
No full textInternational audienceHeavy vanadium (V) isotope compositions of bulk silicate Earth (BSE) and Mars (BSM) relative to chondrites have been suggested to result from high pressure-high temperature core segregation processes on terrestrial planets. However, an alternative possibility is that these heavy V isotope signatures could reflect inheritance from their differentiated planetary building blocks if, for instance, early formed planetesimals underwent V isotope fractionation during differentiation and/or magma ocean evaporation. To test this hypothesis, we report the first V isotope compositions of 40 achondrites (eucrites and diogenites, angrites, ureilites, and acapulcoites-lodranites) originating from four distinct parent bodies. We find that the bulk silicate portions of (4) Vesta and the Angrite Parent Body (APB) exhibit heavy V isotope signatures relative to chondrites, comparable to (or greater than) BSM, but lighter than BSE. On the contrary, the Ureilite Parent Body (UPB) and the Acapulcoite/Lodranite Parent Body (ALPB) are indistinguishable from the chondritic value. To investigate the origin of these V isotope variations, we combine V isotope data with the systematics of other elements. First, we show that differentiated planetary bodies do not exhibit clear V–Sr isotope covariations similar to those recently observed for calcium-aluminum-rich inclusions (CAIs). Only the heavy V isotope signature of (4) Vesta could have potentially resulted from accretionary and/or magma ocean volatilization processes (reflecting ∼0.6 % V and Sr loss). To account for the heavy V but chondritic Sr isotope compositions of the APB, BSM, and Moon, we suggest either (i) extremely large isotope fractionation of V during core formation, or (ii) significantly higher metal-silicate partition coefficients (i.e., more siderophile V) than expected based on experimental data and planetary body conditions. Alternatively, conditions of nebular evaporation recorded in CAIs may not apply to planetary evolution, or the volatilities of V and Sr may differ significantly under early planetary conditions. Similarly, we observe no strong correlation between V and evaporation-sensitive elements like K, likely due to K's much higher volatility compared to V. Potential correlations between V and elements such as Mg (R² = 0.98), Si (R² = 0.81), and Fe (R² = 0.46) suggest that these elements – in particular Mg – may exhibit volatilities closer to V than to K or Sr during planetary evaporation. Explaining bulk δ51V variations through vapor–melt fractionation – rather than V partitioning into the core – would alleviate potential conflicts between our data and previous modeling based on available experimental results regarding V metal-silicate partitioning. In any case, the lack of a V isotope anomaly for the UPB and ALPB indicates that the processes responsible for the heavy V isotope compositions of (4) Vesta, the APB, and the terrestrial planets did not occur on these two bodies. This result is consistent with a lack of global magma ocean formation on these parent bodies, as independently suggested by the preservation of mass independent oxygen isotope heterogeneities throughout the mantles of both parent bodies
Black hole photon ring beyond General Relativity: an integrable parametrization
No full textInternational audienceIn recent years, the shape of the photon ring in black holes images has been argued to provide a sharp test of the Kerr hypothesis for future black hole imaging missions. In this work, we confront this proposal to beyond Kerr geometries and investigate the degeneracy in the estimations of the black hole parameters using the circlipse shape proposed by Gralla and Lupsasca. To that end, we consider a model-independent parametrization of the deviations to the Kerr black hole geometry, dubbed Kerr off shell (KOS), which preserves the fundamental symmetry structure of Kerr known as the Killing tower. Besides exhibiting a Killing tensor and thus a Carter-like constant, all the representants of this family also possess a Killing-Yano tensor and are of Petrov type D. The allowed deviations to Kerr, selected by the symmetry, are encoded in two free functions which depend respectively on the radial and polar angle coordinates. Using the symmetries, we provide an analytic study of the radial and polar motion of photon trajectories generating the critical curve, to which the subrings composing the photon ring converge. This allows us to derive a ready-to-use closed formula for the parametric critical curve in term of the free functions parametrizing the deviations to Kerr. Using this result, we confront the circlipse fitting function to four examples of Kerr-like objects and we show that it admits a high degree of degeneracy. At a given inclination, the same circlipse can fit both a Kerr black hole of a given mass and spin or a modified rotating black hole with different mass and spin parameters and a new parameter . Therefore, future tests of the Kerr hypothesis could be achieved only provided one can measure independently the mass and spin of the black hole to break this degeneracy