Operating an atom interferometer beyond its linear range

In this paper, we show that an atom interferometer inertial sensor, when associated to the auxiliary measurement of external vibrations, can be operated beyond its linear range and still keep a high acceleration sensitivity. We propose and compare two measurement procedures (fringe fitting and nonlinear lock) that can be used to extract the mean phase of the interferometer when the interferometer phase fluctuations exceed $2\pi$. Despite operating in the urban environment of inner Paris without any vibration isolation, the use of a low noise seismometer for the measurement of ground vibrations allows our atom gravimeter to reach at night a sensitivity as good as $5.5\times10^{-8}$g at 1 s. Robustness of the measurement to large vibration noise is also demonstrated by the ability of our gravimeter to operate during an earthquake with excellent sensitivity. Our high repetition rate allows for recovering the true low frequency seismic vibrations, ensuring proper averaging. Such techniques open new perspectives for applications in other fields, such as navigation and geophysics.Comment: 20 pages, 8 figure

Quantum adiabatic elimination at arbitrary order for photon number measurement

International audienceAdiabatic elimination is a perturbative model reduction technique based on timescale separation and often used to simplify the description of composite quantum systems. We here analyze a quantum experiment where the perturbative expansion can be carried out to arbitrary order, such that: (i) we can formulate in the end an exact reduced model in quantum form; (ii) as the series provides accuracy for ever larger parameter values, we can discard any condition on the timescale separation, thereby analyzing the intermediate regime where the actual experiment is performing best; (iii) we can clarify the role of some gauge degrees of freedom in this model reduction technique

Vibration rejection on atomic gravimeter signal using a seismometer

International audienc

Vibration rejection on atomic gravimeter signal using a seismometer

International audienc

Vibration rejection on atomic gravimeter signal using a seismometer

International audienc

Multiplexed photon number measurement

Main text and supplementary materialThe evolution of quantum systems under measurement is a central aspect of quantum mechanics. When a two level system -- a qubit -- is used as a probe of a larger system, it naturally leads to answering a single yes-no question about the system state followed by its corresponding quantum collapse. Here, we report an experiment where a single superconducting qubit is counter-intuitively able to answer not a single but nine yes-no questions about the number of photons in a microwave resonator at the same time. The key ingredients are twofold. First, we exploit the fact that observing the color of a qubit carries additional information to the conventional readout of its state. The qubit-system interaction is hence designed so that the qubit color encodes the number of photons in the resonator. Secondly, we multiplex the qubit color observation by recording how the qubit reflects a frequency comb. Interestingly the amount of extracted information reaches a maximum at a finite drive amplitude of the comb. We evidence it by direct Wigner tomography of the quantum state of the resonator. Our experiment unleashes the full potential of quantum meters by bringing the measurement process in the frequency domain

Fabriquer l’Égalité. Manifeste pour en finir avec le sexisme dans l’économie sociale et solidaire

International audience« Chez nous, il n'y a pas de problèmes ! » Les coopératives, les associations, les mutuelles et les réseaux de l'économie sociale et solidaire (ESS) affichent leur attachement aux valeurs d'égalité et de solidarité (« Normal, c'est dans notre ADN »). Sauf que des inégalités fortes persistent dans l'ESS, en termes de gouvernance, de mixité des métiers, de salaires, de conditions de travail... Face au déni des inégalités, il y a nécessité à renforcer le pouvoir d'agir des personnes ? qu'elles soient salariées, associées, élues de l'ESS. Si l'on ne fait rien, on laisse se perpétuer les stéréotypes, le sexisme, l'invisibilisation des femmes, les rapports de domination. D'autant que de très nombreuses femmes de l'ESS travaillent dans les métiers du care où d'autres rapports de pouvoir se superposent. Les milieux dits « progressistes » sont aussi sexistes, force est de le constater (de l'ESS à l'affaire Baupin en passant par la Ligue du Lol). Mais c'est aussi dans ces milieux (et dans l'ESS) que la parole se peut plus facilement se libérer et la mobilisation s'organiser. Ce texte est une invitation à aller collectivement vers l'égalité, à expérimenter de nouvelles pratiques internes pour que le potentiel de transformation sociétale et d'innovation affiché par les structures de l'ESS ne reste pas théorique. Il constitue un outil d'actions afin de débloquer les peurs et les résistances qui entourent encore le sujet de l'égalité femmes-hommes. (source: 4e de couverture