arXiv subjects

Jérémie Richard

Publications and source records attributed to Jérémie Richard.

5 recordsLinked to original sources

arXiv2024

Absolute quantum gravimeters and gradiometers for field measurements

Gravity measurements provide valuable information on the mass distribution below the earth surface relevant to various areas of geosciences such as hydrology, geodesy, geophysics, volcanology, and natural resources management. During the past decades, the needs for sensitivity, robustness, compactness, and transportability of instruments measuring the gravitational acceleration have constantly increased. Today, applications typically call for 1 $μ\mathrm{Gal} = 10 \mathrm{nm.s}^{-2}$ ~ $10^{-9}$ g resolution on time scales ranging from minutes to years. Absolute Quantum Gravimeters (AQGs) based on matter-wave interferometry with laser-cooled atoms address all these challenges at once, even in uncontrolled environments. Furthermore, to date, quantum gravimeters are the only technology capable of providing continuous absolute gravity data over long measurement durations (~1 day to months or more). In this paper we recall the AQG working principle and present the reproducible high performance at the μGal level on all 16 units fabricated so far. We also describe recent progress on the Differential Quantum Gravimeter (DQG) which measures simultaneously the mean gravitational acceleration and its vertical gradient at the level of $10 \mathrm{nm.s}^{-2}$ and $1$ E (1 E[eotvos] = $10^{-9}$ s$^{-2}$) respectively.

physics.atom-ph↗

arXiv2019

Ultracold Atoms in Disordered Potentials: Elastic Scattering Time in the Strong Scattering Regime

We study the elastic scattering time $τ_\mathrm{s}$ of ultracold atoms propagating in optical disordered potentials in the strong scattering regime, going beyond the recent work of J. Richard \emph{et al.} \textit{Phys. Rev. Lett.} \textbf{122} 100403 (2019). There, we identified the crossover between the weak and the strong scattering regimes by comparing direct measurements and numerical simulations to the first order Born approximation. Here we focus specifically on the strong scattering regime, where the first order Born approximation is not valid anymore and the scattering time is strongly influenced by the nature of the disorder. To interpret our observations, we connect the scattering time $τ_\mathrm{s}$ to the profiles of the spectral functions that we estimate using higher order Born perturbation theory or self-consistent Born approximation. The comparison reveals that self-consistent methods are well suited to describe $τ_\mathrm{s}$ for Gaussian-distributed disorder, but fails for laser speckle disorder. For the latter, we show that the peculiar profiles of the spectral functions, as measured independently in V. Volchkov \emph{et al.} \textit{Phys. Rev. Lett.} \textbf{120}, 060404 (2018), must be taken into account. Altogether our study characterizes the validity range of usual theoretical methods to predict the elastic scattering time of matter waves, which is essential for future close comparison between theory and experiments, for instance regarding the ongoing studies on Anderson localization.

cond-mat.quant-gas↗

arXiv2019

Elastic Scattering Time of Matter-Waves in Disordered Potentials

We report on an extensive study of the elastic scattering time $\tauS$ of matter-waves in optical disordered potentials. Using direct experimental measurements, numerical simulations and comparison with first-order Born approximation based on the knowledge of the disorder properties, we explore the behavior of $\tauS$ over more than three orders of magnitude, spanning from the weak to the strong scattering regime. We study in detail the location of the crossover and, as a main result, we reveal the strong influence of the disorder statistics, especially on the relevance of the widely used Ioffe-Regel-like criterion $k\lS\sim 1$. While it is found to be relevant for Gaussian-distributed disordered potentials, we observe significant deviations for laser speckle disorders that are commonly used with ultracold atoms. Our results are crucial for connecting experimental investigation of complex transport phenomena, such as Anderson localization, to microscopic theories.

cond-mat.quant-gas↗

arXiv2019

Suppression and Revival of Weak Localization through Control of Time-Reversal Symmetry

We report on the observation of suppression and revival of coherent backscattering of ultra-cold atoms launched in an optical disorder and submitted to a short dephasing pulse, as proposed in a recent paper of T. Micklitz \textit{et al.} [arXiv:1406.6915]. This observation, in a quasi-2D geometry, demonstrates a novel and general method to study weak localization by manipulating time reversal symmetry in disordered systems. In future experiments, this scheme could be extended to investigate higher order localization processes at the heart of Anderson (strong) localization.

cond-mat.quant-gas↗

arXiv2012

Coherent Backscattering of Ultracold Atoms

We report on the direct observation of coherent backscattering (CBS) of ultracold atoms, in a quasi-two-dimensional configuration. Launching atoms with a well-defined momentum in a laser speckle disordered potential, we follow the progressive build up of the momentum scattering pattern, consisting of a ring associated with multiple elastic scattering, and the CBS peak in the backward direction. Monitoring the depletion of the initial momentum component and the formation of the angular ring profile allows us to determine microscopic transport quantities. The time resolved evolution of the CBS peak is studied and is found a fair agreement with predictions, at long times as well as at short times. The observation of CBS can be considered a direct signature of coherence in quantum transport of particles in disordered media. It is responsible for the so called weak localization phenomenon, which is the precursor of Anderson localization.

physics.atom-ph↗