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361 Research products, page 1 of 37

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  • Swiss National Science Foundation
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  • Publication . Preprint . Article . Conference object . 2022
    Open Access
    Authors: 
    Ioannou, Marie; Pereira, Maria Ana; Rusca, Davide; Grünenfelder, Fadri; Boaron, Alberto; Perrenoud, Matthieu; Abbott, Alastair,; Sekatski, Pavel; Bancal, Jean-Daniel; Maring, Nicolas; +2 more
    Publisher: SPIE
    Country: France
    Project: SNSF | Quantum correlations in n... (192244)

    We present protocols for quantum key distribution in a prepare-and-measure setup with an asymmetric level of trust. While the device of the sender (Alice) is partially characterized, the receiver's (Bob's) device is treated as a black-box. The security of the protocols is based on the assumption that Alice's prepared states have limited overlaps, but no explicit bound on the Hilbert space dimension is required. The protocols are immune to attacks on the receiver's device, such as blinding attacks. The users can establish a secret key while continuously monitoring the correct functioning of their devices through observed statistics. We report a proof-of-principle demonstration, involving mostly off-the-shelf equipment, as well as a high-efficiency superconducting nanowire detector. A positive key rate is demonstrated over a 4.8 km low-loss optical fiber with finite-key analysis. The prospects of implementing these protocols over longer distances is discussed.

  • Publication . Conference object . 2022
    Closed Access
    Authors: 
    Filippo Maria Zerbi; François Bouchy; Johan P. U. Fynbo; Roberto Maiolino; Nikolai Piskunov; R. Rebolo Lopez; Nuno C. Santos; Klaus G. Strassmeier; Stéphane Udry; L. Vanzi; +42 more
    Publisher: SPIE
    Country: France
    Project: SNSF | Exploring exoplanets with... (152721)

    International audience; The current instrumentation plan for the E-ELT foresees a High Resolution Spectrograph conventionally indicated as HIRES. Shaped on the study of extra-solar planet atmospheres, Pop-III stars and fundamental physical constants, HIRES is intended to embed observing modes at high-resolution (up to R=150000) and large spectral range (from the blue limit to the K band) useful for a large suite of science cases that can exclusively be tackled by the E-ELT. We present in this paper the solution for HIRES envisaged by the "HIRES initiative", the international collaboration established in 2013 to pursue a HIRES on E-ELT.

  • Publication . Article . Conference object . Preprint . 2021 . Embargo End Date: 01 Jan 2021
    Open Access
    Authors: 
    Justinas Pupeikis; Benjamin Willenberg; Francois Bruno; Mike Hettich; Alexander Nussbaum-Lapping; Matthias Golling; Carolin P. Bauer; Sandro L. Camenzind; Abdelmjid Benayad; Patrice Camy; +3 more
    Publisher: arXiv
    Country: France
    Project: SNSF | Next Generation Microscop... (203709), SNSF | Dual-comb spectroscopy ba... (180933), SNSF | Next Generation Microscop... (203709), SNSF | Dual-comb spectroscopy ba... (180933)

    We present a free-running 80-MHz dual-comb polarization-multiplexed solid-state laser which delivers 1.8 W of average power with 110-fs pulse duration per comb. With a high-sensitivity pump-probe setup, we apply this free-running dual-comb laser to picosecond ultrasonic measurements. The ultrasonic signatures in a semiconductor multi-quantum-well structure originating from the quantum wells and superlattice regions are revealed and discussed. We further demonstrate ultrasonic measurements on a thin-film metalized sample and compare these measurements to ones obtained with a pair of locked femtosecond lasers. Our data show that a free-running dual-comb laser is well-suited for picosecond ultrasonic measurements and thus it offers a significant reduction in complexity and cost for this widely adopted non-destructive testing technique.

  • Publication . Preprint . Conference object . Article . 2021
    Open Access
    Authors: 
    Peterson Yuhala; Pascal Felber; Valerio Schiavoni; Alain Tchana;
    Publisher: IEEE
    Country: France
    Project: SNSF | PersiST: In-Memory Persis... (178822)

    International audience; With the increasing popularity of cloud based machine learning (ML) techniques there comes a need for privacy and integrity guarantees for ML data. In addition, the significant scalability challenges faced by DRAM coupled with the high access-times of secondary storage represent a huge performance bottleneck for ML systems. While solutions exist to tackle the security aspect, performance remains an issue. Persistent memory (PM) is resilient to power loss (unlike DRAM), provides fast and fine-granular access to memory (unlike disk storage) and has latency and bandwidth close to DRAM (in the order of ns and GB/s, respectively). We present PLINIUS, a ML framework using Intel SGX enclaves for secure training of ML models and PM for fault tolerance guarantees. PLINIUS uses a novel mirroring mechanism to create and maintain (i) encrypted mirror copies of ML models on PM, and (ii) encrypted training data in byteaddressable PM, for near-instantaneous data recovery after a system failure. Compared to disk-based checkpointing systems, PLINIUS is 3.2× and 3.7× faster respectively for saving and restoring models on real PM hardware, achieving robust and secure ML model training in SGX enclaves.

  • Publication . Conference object . Preprint . Other literature type . Article . 2021
    Open Access
    Authors: 
    Remi Dulong; Rafael Pires; Andreia Correia; Valerio Schiavoni; Pedro Ramalhete; Pascal Felber; Gaël Thomas;
    Publisher: IEEE
    Countries: Switzerland, France
    Project: SNSF | PersiST: In-Memory Persis... (178822)

    This paper introduces NVCache, an approach that uses a non-volatile main memory (NVMM) as a write cache to improve the write performance of legacy applications. We compare NVCache against file systems tailored for NVMM (Ext4-DAX and NOVA) and with I/O-heavy applications (SQLite, RocksDB). Our evaluation shows that NVCache reaches the performance level of the existing state-of-the-art systems for NVMM, but without their limitations: NVCache does not limit the size of the stored data to the size of the NVMM, and works transparently with unmodified legacy applications, providing additional persistence guarantees even when their source code is not available. Comment: 13 pages, 7 figures, to be published in the 51th IEEE/IFIP International Conference on Dependable Systems and Networks (DSN 21)

  • Publication . Preprint . Article . Conference object . 2021
    Open Access English
    Authors: 
    Armin Tavakoli; Emmanuel Zambrini Cruzeiro; Roope Uola; Alastair A. Abbott;
    Publisher: HAL CCSD
    Country: France
    Project: SNSF | From Bell nonlocality to ... (188276), SNSF | Certification of quantum ... (194800)

    We introduce a hierarchy of semidefinite relaxations of the set of quantum correlations in generalised contextuality scenarios. This constitutes a simple and versatile tool for bounding the magnitude of quantum contextuality. To illustrate its utility, we use it to determine the maximal quantum violation of several noncontextuality inequalities whose maximum violations were previously unknown. We then go further and use it to prove that certain preparation-contextual correlations cannot be explained with pure states, thereby showing that mixed states are an indispensable resource for contextuality. In the second part of the paper, we turn our attention to the simulation of preparation-contextual correlations in general operational theories. We introduce the information cost of simulating preparation contextuality, which quantifies the additional, otherwise forbidden, information required to simulate contextual correlations in either classical or quantum models. In both cases, we show that the simulation cost can be efficiently bounded using a variant of our hierarchy of semidefinite relaxations, and we calculate it exactly in the simplest contextuality scenario of parity-oblivious multiplexing. See also the related work arXiv:2010.05853. Code package SDP relaxations of quantum contextuality available at: https://github.com/alastair-abbott/contextuality-hierarchy. contextuality-hierarchy

  • Open Access English
    Authors: 
    Mahdi Khoramshahi; Guillaume Morel; Nathanaël Jarrassé;
    Publisher: HAL CCSD
    Country: France
    Project: SNSF | Intent-aware control for ... (191698), ANR | BYCEPS (ANR-18-CE19-0004)

    International audience; Many human-robot collaboration scenarios can be seen as a redundant leader-follower setup where the human (i.e., the leader) can potentially perform the task without the assistance of the robot (i.e., the follower). Thus, the goal of the collaboration, beside stable execution of the task, is to reduce the human cost; e.g., ergonomic, or cognitive cost. Such system redundancies (where the same task be achieved in different manner) can also be exploited as a communication channel for the human to convey his/her intention to the robot; since it is essential for the overall performance (both execution and assistance) that the follower recognizes the intended task in an online fashion. Having an estimation for the intended task, the robot can assist the human by reducing the human cost over the task null-space; i.e., the null-space which arises from the overall system redundancies with respect to the intended task. With the prospective of supernumerary and prosthetic robots, in this work, we primarily focus on serial manipulation in which the proximal/distal part of the kinematic chain is controlled by the leader/follower respectively. By exploiting kinematic redundancies for intention-recognition and costminimization, our proposed control strategy (for the follower) ensures assistance under stable execution of the task. Our results (simulations and preliminary experimentation) show the efficacy of our method in providing a seamless robotic assistance (i.e., improving human posture) toward human intended tasks (i.e., reaching motions) for wearable robotics.

  • Publication . Preprint . Conference object . Article . 2021
    Open Access English
    Authors: 
    Basil Maag; Stefan Feuerriegel; Mathias Kraus; Maytal Saar-Tsechansky; Thomas Züger;
    Publisher: ACM
    Country: Switzerland
    Project: SNSF | Data-driven health manage... (186932)

    In medicine, comorbidities refer to the presence of multiple, co-occurring diseases. Due to their co-occurring nature, the course of one comorbidity is often highly dependent on the course of the other disease and, hence, treatments can have significant spill-over effects. Despite the prevalence of comorbidities among patients, a comprehensive statistical framework for modeling the longitudinal dynamics of comorbidities is missing. In this paper, we propose a probabilistic model for analyzing comorbidity dynamics over time in patients. Specifically, we develop a coupled hidden Markov model with a personalized, non-homogeneous transition mechanism, named Comorbidity-HMM. The specification of our Comorbidity-HMM is informed by clinical research: (1) It accounts for different disease states (i. e., acute, stable) in the disease progression by introducing latent states that are of clinical meaning. (2) It models a coupling among the trajectories from comorbidities to capture co-evolution dynamics. (3) It considers between-patient heterogeneity (e. g., risk factors, treatments) in the transition mechanism. Based on our model, we define a spill-over effect that measures the indirect effect of treatments on patient trajectories through coupling (i. e., through comorbidity co-evolution). We evaluated our proposed Comorbidity-HMM based on 675 health trajectories where we investigate the joint progression of diabetes mellitus and chronic liver disease. Compared to alternative models without coupling, we find that our Comorbidity-HMM achieves a superior fit. Further, we quantify the spill-over effect, that is, to what extent diabetes treatments are associated with a change in the chronic liver disease from an acute to a stable disease state. To this end, our model is of direct relevance for both treatment planning and clinical research in the context of comorbidities.

  • Publication . Article . Conference object . External research report . Report . 2021
    Open Access English
    Authors: 
    Nicolas Berman; Mathieu Couttenier; Raphael Soubeyran;
    Publisher: HAL CCSD
    Country: France
    Project: SNSF | Income Shocks and the Dif... (161451), ANR | Amidex (ANR-11-IDEX-0001), ANR | AMSE (EUR) (ANR-17-EURE-0020), ANR | GREEN-Econ (ANR-16-CE03-0005)

    Localisation : Centre de documentation P. Bartoli, UMR LAMETA, Montpellier (S WPL 2011-08); We investigate how variations in soil fertility affect civil conflicts. We first present a model with heterogeneous land in which variations in input prices (fertilizers) affect appropriable rents and the opportunity costs of fighting. The theory predicts that spikes in input prices increase the likelihood of conflicts through their effect on income and inequality, and that this effect is magnified when soil fertility is naturally more heterogenous. We test these predictions using data on conflict events covering all Sub-Saharan African countries at a spatial resolution of 0.5 x 0.5 degree latitude and longitude over the 1997-2013 period. We combine information on soil characteristics and worldwide variations in fertilizer prices to identify local exogenous changes in input costs. As predicted, variations in soil productivity triggered by variations in fertilizer prices are positively associated with conflicts, especially in cells where land endowments are more heterogeneous. In addition, we find that the distribution of land fertility both within and across ethnic groups affects violence, and that the effect of between-group heterogeneity in soil quality is magnified in densely populated areas. Overall, our findings imply that inequality in access to fertile areas - an issue largely neglected in the literature dealing with the roots of Sub-Saharan African civil wars - constitutes a serious threat to peace at the local-level..

  • Publication . Conference object . Other literature type . 2021
    Open Access
    Authors: 
    Shayan Aziznejad; Emmanuel Soubies; Michael Unser;
    Publisher: IEEE
    Countries: France, Switzerland
    Project: EC | GlobalBioIm (692726), SNSF | Spline methods for the co... (184646)

    International audience; We consider a new stochastic formulation of sparse representations that is based on the family of symmetric α-stable (SαS) distributions. Within this framework, we develop a novel dictionary-learning algorithm that involves a new estimation technique based on the empirical characteristic function. It finds the unknown parameters of an SαS law from a set of its noisy samples. We assess the robustness of our algorithm with numerical examples.

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