Rotations play a detrimental role in achieving ultra-high-performance inertial measurements with an atom interferometer, leading potentially to a total loss of interference contrast and the emergence of dominant phase shift biases. This becomes particularly significant when considering operation in dynamic conditions such as those encountered in Earth orbiting satellites in the perspective of future space gravity missions on-boarding a cold atom accelerometer. We study in this context the impact of rotation on the phase shift and contrast of an atom interferometer and investigate mitigation strategies. An analytical model is derived and compared to experimental demonstrations carried out using an original setup in which the well-controlled proof-mass of a space electrostatic accelerometer is used as the retro-reflection mirror of a cold atom gravimeter. By properly counter-rotating the electrostatic proof-mass, we demonstrate for instance the possibility of recovering the interferometer contrast, otherwise equal to zero, to a level better than 90%, in both cases of constant angular velocities or in presence of angular accelerations. Our results demonstrate the possibility to perform high performance inertial measurements with a cold atom interferometer in a challenging environments.
Rotations play a detrimental role in achieving ultra-high-performance inertial measurements with an atom interferometer, leading potentially to a total loss of interference contrast and the emergence of dominant phase shift biases. This becomes particularly significant when considering operation in dynamic conditions such as those encountered in Earth orbiting satellites in the perspective of future space gravity missions on-boarding a cold atom accelerometer. We study in this context the impact of rotation on the phase shift and contrast of an atom interferometer and investigate mitigation strategies. An analytical model is derived and compared to experimental demonstrations carried out using an original setup in which the well-controlled proof-mass of a space electrostatic accelerometer is used as the retro-reflection mirror of a cold atom gravimeter. By properly counter-rotating the electrostatic proof-mass, we demonstrate for instance the possibility of recovering the interferometer contrast, otherwise equal to zero, to a level better than 90%, in both cases of constant angular velocities or in presence of angular accelerations. Our results demonstrate the possibility to perform high performance inertial measurements with a cold atom interferometer in a challenging environments.
Recent advances in cold atom interferometry have cleared the path for space applications of quantum inertial sensors, whose level of stability is expected to increase dramatically with the longer interrogation times accessible in space. In this study, an in-orbit model is developed for a Mach-Zehnder-type cold-atom accelerometer. Performance tests are realized under different assumptions about the positioning and rotation compensation method, and the impact of various sources of errors on instrument stability is evaluated. Current and future advances for space-based atom interferometry are discussed, and their impact on the performance of quantum sensors on-board satellite gravity missions is investigated in three different scenarios: state-of-the-art scenario(expected to be ready to launch in 5 years), near-future (expected to be launched in the next 10 to 15 years)and far-future scenarios (expected for the next 20 to 25 years). Our results indicate that the highest sensitivity is achievable by positioning the electrostatic accelerometer at the center of mass of the satellite and the quantum accelerometer aside, on the cross-track axis of the satellite. We show that one can achieve a sensitivity level close to 5×10-10m/s2/Hz with the current state-of-the-art technology. We also estimate that in the near and far-future, atom interferometry in space is expected to achieve sensitivity levels of 1×10-11m/s2/Hz and 1×10-12m/s2/Hz, respectively. A roadmap for improvements in atom interferometry is provided that would maximize the performance of future quantum accelerometers, considering their technical capabilities. Finally, the possibility and challenges of having ultra-sensitive atom interferometry in space for future space missions are discussed.
The exquisite precision of atom interferometers has sparked the interest of a large community for uses ranging from fundamental physics to geodesy and inertial navigation. However, their implementation for onboard applications is still limited, not least because rotation and acceleration are intertwined in a single phase shift, which makes the extraction of a useful signal more challenging. Moreover, the spatial separation of the wave packets due to rotations leads to a loss of signal. We present an atom interferometer operating over a large range of random angles, rotation rates and accelerations. A model of the expected phase shift allows us to untangle the rotation and acceleration signals. We also implement a real-time compensation system using fiber-optic gyroscopes and a rotating reference mirror to maintain the full contrast of the interferometer. We demonstrate a single-shot sensitivity to acceleration of 24 μg for rotation rates reaching 14° s−1. Cold atoms inertial sensors offer great precision and sensitivity, yet their use in mobile applications has been hindered by the effects of rotations on their measurements. Here, authors demonstrate an atom interferometer operating over a wide range of orientations and rotation rates, thanks to hybridisation with accelerometers and gyroscopes.
Le but des missions spatiales de gravimétrie est de mesurer le champ de gravité avec une grande précision. Les données récoltées sont utilisées en sciences du climat, en hydrologie, en géophysique et pour mieux comprendre le réchauffement climatique. Ces missions embarquent actuellement des accéléromètres électrostatiques avec une grande sensibilité mais dérivant à long terme. Cette dérive peut être corrigée en recalibrant l'accéléromètre électrostatique avec un accéléromètre à atomes froids ayant une plus importante stabilité. De tels accéléromètres utilisent l'interférométrie atomique pour mesurer l'accélération et une des difficultés de la mesure spatiale est la chute de contraste de l'interféromètre à cause de la rotation du satellite autour de la Terre. Dans cette étude, nous avons mis en place expérimentalement une méthode pour limiter l'impact de la rotation sur l'interféromètre. Le dispositif expérimental est la combinaison d'un accéléromètre électrostatique et d'un interféromètre à atomes froids. La masse d'épreuve de l'électrostatique est employée comme miroir de rétro-réflexion pour l'interféromètre et est très bien contrôlée selon les six dégrées de liberté de l'espace. La méthode utilisée pour limiter l'impact de la rotation consiste à tourner le miroir pour garder la direction de mesure constante pendant l'interféromètre. Avec cette méthode de compensation de la rotation, 99% du contraste a été récupéré. De plus, la phase de l'interféromètre causée par la rotation a été mesuré et modélisée. Avec un modèle fiable, cette phase supplémentaire peut être corrigée de la mesure. Finalement, les performances attendues d'un accéléromètre atomique compensé de la rotation à bord d'un satellite ont été étudiées. Avec les hypothèses choisies, la rotation serait à l'origine d'une incertitude de 7 x 10⁻¹⁰ ms⁻ ² sur la mesure de l'accélération pour un temps d'interrogation de 1 s.
Vers un accéléromètre hybride électrostatique/atomique pour les futures missions spatiales : étude de l'impact de la rotation sur l'interféromètre à atomes froids et réduction de cet impact Le but des missions spatiales de gravimétrie est de mesurer le champ de gravité avec une grande précision. Les données récoltées sont utilisées en sciences du climat, en hydrologie, en géophysique et pour mieux comprendre le réchauffement climatique. Ces missions embarquent actuellement des accéléromètres électrostatiques avec une grande sensibilité mais dérivant à long terme. Cette dérive peut être corrigée en recalibrant l'accéléromètre électrostatique avec un accéléromètre à atomes froids ayant une plus importante stabilité. De tels accéléromètres utilisent l'interférométrie atomique pour mesurer l'accélération et une des difficultés de la mesure spatiale est la chute de contraste de l'interféromètre à cause de la rotation du satellite autour de la Terre. Dans cette étude, nous avons mis en place expérimentalement une méthode pour limiter l'impact de la rotation sur l'interféromètre. Le dispositif expérimental est la combinaison d'un accéléromètre électrostatique et d'un interféromètre à atomes froids. La masse d'épreuve de l'électrostatique est employée comme miroir de rétro-réflexion pour l'interféromètre et est très bien contrôlée selon les six dégrées de liberté de l'espace. La méthode utilisée pour limiter l'impact de la rotation consiste à tourner le miroir pour garder la direction de mesure constante pendant l'interféromètre. Avec cette méthode de compensation de la rotation, 99% du contraste a été récupéré. De plus, la phase de l'interféromètre causée par la rotation a été mesuré et modélisée. Avec un modèle fiable, cette phase supplémentaire peut être corrigée de la mesure. Finalement, les performances attendues d'un accéléromètre atomique compensé de la rotation à bord d'un satellite ont été étudiées. Avec les hypothèses choisies, la rotation serait à l'origine d'une incertitude de 7 x 10⁻¹⁰ ms⁻ ² sur la mesure de l'accélération pour un temps d'interrogation de 1 s.
Classical inertial navigation systems integrate inertial measurements from triads of accelerometers and gyroscopes to determine their position, but the computed trajectory is typically limited by the intrinsic time-varying bias of these inertial sensors. In addition, the exploitation of quantum physics led to the development of matter-wave interferometers, sensitive to inertial effects due to the mass of the atoms. While they are free-falling, these atoms constitute a perfect inertial frame of reference and allow for an absolute measurement with outstanding accuracy and stability. Substantial technical developments have allowed bringing quantum gravimeters to the market, enabling static, long-term measurements. Nevertheless, the use of cold-atom sensors for navigation and positioning still requires addressing many scientific and technological challenges to be compatible with onboard applications such as compactness, measurement continuity and operation in the presence of strong vibrations and rotations.The Joint Laboratory iXAtom brings together the expertise of the Laboratoire de Photonique, Numérique et Nanosciences (LP2N) in matter-wave interferometry and the French technology company Exail, specialized in high-performance inertial navigation systems and industrial quantum sensors, with the aim of building a new generation of high-end inertial sensors through the hybridization of classical accelerometers and gyroscopes with quantum sensors based on matter-wave interferometry.After successfully building a multi-axis cold-atom interferometer measuring the three components of the acceleration vector with a static apparatus, this quantum inertial sensor has been fully hybridized with a triad of classical accelerometers, increasing the bandwidth and dynamic range without the usual limitation due to the bias drift of the mechanical accelerometers. Moreover, this hybridization technique features a real-time correction of the laser phase which allows retrieving the acceleration information out of atomic fringes scrambled by parasitic vibrations. As regards the rotations of the instrument throughout an interferometer, their compensation remains the next major issue to tackle for strapdown applications as they induce a drastic reduction of the atomic fringes’ visibility coupled to a scrambling of the interferometric phase shift.This thesis work focuses on the mitigation of the rotation-induced performance deterioration of the hybrid accelerometer. Through a theoretical investigation, a model for both the angular velocity-dependent decay of the fringes contrast and the systematic phase shift arising from the complex trajectory of the atomic cloud in the rotating frame of the interrogation laser is established. A real-time rotation compensation system, employing the measurement of the rotation rate with high-end fiber-optic gyroscopes to drive a piezo-actuated tip-tilt platform, has been implemented to stabilize the orientation of the interrogation laser in the external frame in order to preserve the contrast of the atomic interference pattern and extend the measurement range of the rotating atom interferometer. A rectification of the theoretical model accounting for the rotation of the laser as well as the hybridization with the classical accelerometers enables reconstructing the atomic fringes and retrieving the inertial measurement, paving the way for strapdown onboard hybrid accelerometry.
In recent years there has been significant activity in research and development of high sensitivity accelerometers and gyroscopes using atom interferometers. In these devices, a fringe shift in the interference of atom de Broglie waves indicates the rotation rate of the interferometer relative to an inertial frame of reference. In both optical and atomic conventional Sagnac interferometers, the resultant phase difference due to rotation is independent of the wave velocity. However, we show that if an atom interforemeter is enclosed in a Faraday cage which is at some potential, the phase difference of the counter-propagating waves is proportional to the inverse square of the particle velocity and it is proportional to the applied potential. This is due to Aharonov-Bohm effect and it can be used to increase the rotation sensitivity of atom interferometers.