Manipulation cohérente des états d’Andreev dans un contact atomique

Localized electronic states, called Andreev bound states, appear in weak-links placed between superconducting electrodes. The experiments presented in this thesis explore the coherence properties of these states. Single atom contacts between aluminum electrodes are used as weak links. In order to isolate and probe these states, the atomic contacts are integrated in amicrowave cavity.In a first series of experiments, it is shown that Andreev states can be used to define a quantumbit, “the Andreev qubit”, which is controlled using microwave pulses.Measurements of the lifetime and coherence time of this qubit are thoroughly analyzed.In a second series of experiments, the interaction between the Andreev qubit and the microwave cavity are used to determine the number of photons present in the cavity as a function of the power of microwave pulses at its eigenfrequency.Finally, quantum and parity jumps are observed in continuous measurements of the state of the Andreev dot.Des états électroniques localisés apparaissent dans les liens faibles entre électrodes supraconductrices : les états d’Andreev. Les expériences présentées dans cette thèse explorent les propriétés de cohérence quantique de ces états, en utilisant comme liens faibles des contacts à un atome entre des électrodes d’aluminium. Les contacts atomiques sont intégrés dans une cavité microonde qui permet à la fois de les isoler et de les sonder.Dans une première série d’expériences, il est montré qu’on peut utiliser les états d’Andreev pour définir un bit quantique, le « qubit d’Andreev », qu’on contrôle à l’aide d’impulsions micro-onde.Les mesures des temps de vie de cohérence de ce qubit sont analysées en détail.Dans une deuxième série d’expérience,l’interaction entre le qubit d’Andreev et le résonateur micro-onde est utilisée pour quantifier le nombre de photons présents dans le résonateur en fonction de la puissance d’impulsions microonde à sa fréquence propre.Enfin, des sauts quantiques et des sauts de parités ont observés dans des mesures continues de l’état du qubit d’Andreev

New Developments for Commercial Quantum Gravimeters

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Caractérisation d'un gravimètre quantique différentiel

National audienc

Pushing the stability of a Differential Quantum Gravimeter below 1Eötvös/1µGal

International audienceOne year after the first signals were obtained with the Differential Quantum Gravimeter (DQG) developed by muquans, we report on the new performances of the instrument. DQG is a unique instrument that combines the ability of simultaneously measuring the local gravity acceleration and its vertical gradient with an industry-grade geophysics-oriented design. Relying on a similar physical principle and same technologies developed for our absolute quantum gravimeters (AQG) [1], a single vertical laser beam simultaneously measures the vertical acceleration experienced by two sets of free-falling laser-cooled atoms from different heights. The vertical acceleration gives a direct access to g, and the difference of both measurements yields to vertical gravity gradient . [2,3]. Our demonstrator has been operational for a year and demonstrated best sensitivities of 53 E/?t, and 360nm/s<SUP>2</SUP>/?t, on the second floor of a university building. Long term stabilities below 1E and 10nm/s<SUP>2</SUP> levels have been obtained on 60 hours long measurements. After presenting the instrument and results, the talk will present the studies led to further improve the capabilities and performances. We will finally present ongoing works on mass detection experiments. Such experiments aim at assessing the accuracy of the instrument as well as its ability to detect and monitor underground density variations, opening new perspectives for applications in geodesy and hydrology.This work has been supported by the DGA, the French Department of Defense, and the ANR GRADUS. [1] V. Ménoret et al., "Gravity measurements below 10?9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)[2] M. J. Snadden et al. "Measurement of the Earth's Gravity Gradient with an Atom Interferometer-Based Gravity Gradiometer" , Phys. Rev. Lett. 81, 971 (1998) [3] R. Caldani et al. "Simultaneous accurate determination of both gravity and its vertical gradient", Phys. Rev. A 99, 033601 (2019

Pushing the stability of a Differential Quantum Gravimeter below 1Eötvös/1µGal

International audienceOne year after the first signals were obtained with the Differential Quantum Gravimeter (DQG) developed by muquans, we report on the new performances of the instrument. DQG is a unique instrument that combines the ability of simultaneously measuring the local gravity acceleration and its vertical gradient with an industry-grade geophysics-oriented design. Relying on a similar physical principle and same technologies developed for our absolute quantum gravimeters (AQG) [1], a single vertical laser beam simultaneously measures the vertical acceleration experienced by two sets of free-falling laser-cooled atoms from different heights. The vertical acceleration gives a direct access to g, and the difference of both measurements yields to vertical gravity gradient . [2,3]. Our demonstrator has been operational for a year and demonstrated best sensitivities of 53 E/?t, and 360nm/s<SUP>2</SUP>/?t, on the second floor of a university building. Long term stabilities below 1E and 10nm/s<SUP>2</SUP> levels have been obtained on 60 hours long measurements. After presenting the instrument and results, the talk will present the studies led to further improve the capabilities and performances. We will finally present ongoing works on mass detection experiments. Such experiments aim at assessing the accuracy of the instrument as well as its ability to detect and monitor underground density variations, opening new perspectives for applications in geodesy and hydrology.This work has been supported by the DGA, the French Department of Defense, and the ANR GRADUS. [1] V. Ménoret et al., "Gravity measurements below 10?9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)[2] M. J. Snadden et al. "Measurement of the Earth's Gravity Gradient with an Atom Interferometer-Based Gravity Gradiometer" , Phys. Rev. Lett. 81, 971 (1998) [3] R. Caldani et al. "Simultaneous accurate determination of both gravity and its vertical gradient", Phys. Rev. A 99, 033601 (2019

Recent advances in quantum gravity sensors

International audienc

New Developments for Commercial Quantum Gravimeters

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New Developments for Commercial Quantum Gravimeters

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Compact differential gravimeter at the quantum projection-noise limit

International audienc

New Developments for Commercial Quantum Gravimeters

International audienc