1,500 research outputs found
Compensation of Beer-Lambert attenuation using non-diffracting Bessel beams
We report on a versatile method to compensate the linear attenuation in a
medium, independently of its microscopic origin. The method exploits
diffraction-limited Bessel beams and tailored on-axis intensity profiles which
are generated using a phase-only spatial light modulator. This technique for
compensating one of the most fundamental limiting processes in linear optics is
shown to be efficient for a wide range of experimental conditions (modifying
the refractive index and the attenuation coefficient). Finally, we explain how
this method can be advantageously exploited in applications ranging from
bio-imaging light sheet microscopy to quantum memories for future quantum
communication networks
Regularized Contextual Bandits
International audienceWe consider the stochastic contextual bandit problem with additional regularization. The motivation comes from problems where the policy of the agent must be close to some baseline policy known to perform well on the task. To tackle this problem we use a nonparametric model and propose an algorithm splitting the context space into bins, solving simultaneously-and independently-regularized multi-armed bandit instances on each bin. We derive slow and fast rates of convergence, depending on the unknown complexity of the problem. We also consider a new relevant margin condition to get problem-independent convergence rates, yielding intermediate rates interpolating between the aforementioned slow and fast rates
Phase diagram of one-dimensional driven-dissipative exciton-polariton condensates
We consider a one-dimensional driven-dissipative exciton-polariton condensate
under incoherent pump, described by the stochastic generalized Gross-Pitaevskii
equation. It was shown that the condensate phase dynamics maps under some
assumptions to the Kardar-Parisi-Zhang (KPZ) equation, and the temporal
coherence of the condensate follows a stretched exponential decay characterized
by KPZ universal exponents. In this work, we determine the main mechanisms
which lead to the departure from the KPZ phase, and identify three possible
other regimes: (i) a soliton-patterned regime at large interactions and weak
noise, populated by localized structures analogue to dark solitons; (ii) a
vortex-disordered regime at high noise and weak interactions, dominated by
point-like phase defects in space-time; (iii) a defect-free reservoir-textured
regime where the adiabatic approximation breaks down. We characterize each
regime by the space-time maps, the first-order correlations, the momentum
distribution and the density of topological defects. We thus obtain the phase
diagram at varying noise, pump intensity and interaction strength. Our
predictions are amenable to observation in state-of-art experiments with
exciton-polaritons
Projet REPAIR: Restauration des patchs anthropiques dans l’herbier de Posidonie
REPAIR14. Life below water13. Climate actio
Enhancing field GP engagement in hospital-based studies. Rationale, design, main results and participation in the diagest 3-GP motivation study
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