Pulse shaping with birefringent crystals: a tool for quantum metrology

A method for time differentiation based on a Babinet-Soleil-Bravais compensator is introduced. The complex transfer function of the device is measured using polarization spectral interferometry. Time differentiation of both the pulse field and pulse envelope are demonstrated over a spectral width of about 100 THz with a measured overlap with the objective mode greater than 99.8%. This pulse shaping technique is shown to be perfectly suited to time metrology at the quantum limit

Precision measurements with photon-subtracted or photon-added Gaussian states

Photon-subtracted and photon-added Gaussian states are amongst the simplest non-Gaussian states that are experimentally available. It is generally believed that they are some of the best candidates to enhance sensitivity in parameter extraction. We derive here the quantum Cram\'er-Rao bound for such states and find that for large photon numbers photon-subtraction or -addition only leads to a small correction of the quantum Fisher information (QFI). On the other hand a divergence of the QFI appears for very small squeezing in the limit of vanishing photon number in the case of photon subtraction, implying an arbitrarily precise measurement with almost no light. However, at least for the standard and experimentally established preparation scheme, the decreasing success probability of the preparation in that limit exactly cancels the divergence, leading to finite sensitivity per square root of Hertz, when the duration of the preparation is taken into account.Comment: 19 pages, 3 figure

Local unified models of backscattering from ocean-like surfaces at moderate incidence angles

6 pagesInternational audienceIn the context of electromagnetic wave backscattering from ocean-like surfaces, by using the SSA-1 model, Bourlier et al. proposed a technique to reduce the number of numerical integrations to two for easier numerical implementation. To be consistent with microwave measurements, closed-form expressions of the Fourier coefficients of the backscattering RCS are obtained. For Gaussian statistics, previous work is extended to kernels of unified models expanded up to the order two, like the SSA2 and LCA2

General Cram\'er-Rao bound for parameter estimation using Gaussian multimode quantum resources

Multimode Gaussian quantum light, including multimode squeezed and/or multipartite quadrature entangled light, is a very general and powerful quantum resource with promising applications to quantum information processing and metrology involving continuous variables. In this paper, we determine the ultimate sensitivity in the estimation of any parameter when the information about this parameter is encoded in such Gaussian light, irrespective of the exact information extraction protocol used in the estimation. We then show that, for a given set of available quantum resources, the most economical way to maximize the sensitivity is to put the most squeezed state available in a well-defined light mode. This implies that it is not possible to take advantage of the existence of squeezed fluctuations in other modes, nor of quantum correlations and entanglement between different modes. We show that an appropriate homodyne detection scheme allows us to reach this Cramr-Rao bound. We apply finally these considerations to the problem of optimal phase estimation using interferometric techniques

Correlation effect between transmitter and receiver azimuthal directions on the illumination function from a random rough surface

International audienceThe resolution of some problems of electromagnetic scattering from random rough surfaces implies the derivation of the illumination function, especially when the geometrical optics approximation is valid. In current models, the shadowing e ects occurring for both the trans- mitter and the receiver are assumed to be independent of their azimuthal directions. This assumption makes it possible to compute separately the shadowing probabilities in each di- rection. However, if the transmitter and receiver azimuthal directions are close, these proba- bilities become strongly correlated. In such a con guration, the uncorrelation approximation induces an overestimation of the average illumination function up to 10% as well as a discon- tinuity. In this paper, assuming a surface with Gaussian process, this correlation is taken into account. Comparisons of our model with Monte Carlo simulations are made and show a very good agreement, which validates our approach

Dual-Polarised Radiometer for Road Surface Characterisation

This paper presents measurements using a dual-polarised radiometer operating at 93\ua0GHz to detect ice or water on asphalt in laboratory conditions. The brightness temperatures of both H and V polarizations were measured for a dry surface, liquid water, and ice on asphalt at observation angles of 50\ub0 and 56\ub0. The results presented in this paper demonstrate that the studied road conditions can be identified by the radiometer. The measurements are compared with a model and surface parameters, such as dielectric constant and roughness are fitted and compared to reference values. The experiments and results, described in this article, are the first steps towards the future installation of a polarimetric sensor on a moving vehicle for traffic safety

Rough surface RCS measurements and simulations using the Physical Optics Approximation

International audienceThe objective of this article is to develop innovative approaches to obtain analytical expressions of the Radar Cross Section (RCS) of perfectly-conducting random rough surfaces under the Physical Optics (PO) approximation. The led approaches take into account the specific geometrical properties of the considered surfaces to calculate their RCS. The objective is to reduce the computing time with respect to the numerical PO technique, which requires two numerical integrations. All developed approaches are validated by comparison with a commercial code (the MLFMM of FEKO), used as a reference, and with measurements performed on three selected rough surfaces samples

Comparison of Harmonic, Geometric and Arithmetic means for change detection in SAR time series

International audienceThe amplitude distribution in a SAR image can present a heavy tail. Indeed, very high-valued outliers can be observed. In this paper, we propose the usage of the Harmonic, Geometric and Arithmetic temporal means for amplitude statistical studies along time. In general, the arithmetic mean is used to compute the mean amplitude of time series. In this study, we will show that comparing the behaviour of the Harmonic, Geometric and Arithmetic means, enables a change detection method along SAR time series

Modelling scattering of electromagnetic waves in layered media: An up-to-date perspective

This paper addresses the subject of electromagnetic wave scattering in layered media, thus covering the recent progress achieved with different approaches. Existing theories and models are analyzed, classified, and summarized on the basis of their characteristics. Emphasis is placed on both theoretical and practical application. Finally, patterns and trends in the current literature are identified and critically discussed

Electromagnetic Wave Sensing in Complex Scenarios: Scattering Models and Applications

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