We study two hybridization algorithms that are used for combining a quantum inertial sensor based on atom interferometry with a classical inertial sensor for onboard acceleration measurements. The first is based on the direct extraction of the interferometer phase and has previously been used in seaborne and airborne gravity-measurement campaigns. The second relies on the combination of three consecutive measurements and was originally developed to increase the measurement range of the quantum sensor beyond its linear regime. After comparing their performances using synthetic data, we implement them on acceleration data collected in a recent airborne campaign and evaluate the bias and scale-factor error of the classical sensor. We, then, extend their scope to the dynamical evaluation of other key measurement parameters (e.g., alignment errors). We demonstrate an improvement in the correlation between the measurements of the two accelerometers, and we observe a significant reduction in the error in the estimation of the bias of the classical sensor.
We study two hybridization algorithms that are used for combining a quantum inertial sensor based on atom interferometry with a classical inertial sensor for onboard acceleration measurements. The first is based on the direct extraction of the interferometer phase and has previously been used in seaborne and airborne gravity-measurement campaigns. The second relies on the combination of three consecutive measurements and was originally developed to increase the measurement range of the quantum sensor beyond its linear regime. After comparing their performances using synthetic data, we implement them on acceleration data collected in a recent airborne campaign and evaluate the bias and scale-factor error of the classical sensor. We, then, extend their scope to the dynamical evaluation of other key measurement parameters (e.g., alignment errors). We demonstrate an improvement in the correlation between the measurements of the two accelerometers, and we observe a significant reduction in the error in the estimation of the bias of the classical sensor.
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.
Robust and accurate acceleration tracking remains a challenge in many fields. For geophysics and economic geology, precise gravity mapping requires onboard sensors combined with accurate positioning and navigation systems. Cold atom–based quantum inertial sensors can potentially provide these high-precision instruments. However, current scalar instruments require precise alignment with vector quantities. Here, we present the first hybrid three-axis accelerometer exploiting the quantum advantage to measure the full acceleration vector by combining three orthogonal atom interferometer measurements with a classical navigation-grade accelerometer triad. Its ultralow bias permits tracking the acceleration vector over long time scales, yielding a 50-fold improvement in stability (6 × 10 −8 g ) over our classical accelerometers. We record the acceleration vector at a high data rate (1 kHz), with absolute magnitude accuracy below 10 μ g , and pointing accuracy of 4 μrad. This paves the way toward future strapdown applications with quantum sensors and highlights their potential as future inertial navigation units.
Accurate and stable measurement of inertial quantities is essential in geophysics, geodesy, fundamental physics, and inertial navigation. Here, we present an architecture for a compact cold-atom accelerometer-gyroscope based on a magnetically launched atom interferometer. Characterizing the launching technique, we demonstrate 700–parts per million gyroscope scale factor stability over 1 day, while acceleration and rotation rate bias stabilities of 7 × 10 −7 meters per second squared and 4 × 10 −7 radians per second are reached after 2 days of integration of the cold-atom sensor. Hybridizing it with a classical accelerometer and gyroscope, we correct their drift and bias to achieve respective 100-fold and 3-fold increase on the stability of the hybridized sensor compared to the classical ones. Compared to a state-of-the-art atomic gyroscope, the simplicity and scalability of our launching technique make this architecture easily extendable to a compact full six-axis inertial measurement unit, providing a pathway toward autonomous positioning and orientation using cold-atom sensors.
Inertial navigation is an essential technology for space applications due to its autonomy from external signals and references. In space, inertial navigation systems utilize accelerometers and gyroscopes to measure changes in velocity and orientation, enabling a spacecraft to determine its trajectory independently, assuming the gravitational accelerations are well known. While conventional accelerometers onboard space missions often suffer from a large drift in the frequency range below 10–3Hz, quantum accelerometers can provide highly stable and drift-free measurements of non-gravitational acceleration and consequently improve the spacecraft orbits. This work evaluates the performance of a 3-axis quantum accelerometer for space navigation. In this paper, we analyze the performance of such sensors onboard a spacecraft in a parking orbit around Earth in two scenarios of maintaining a nadir-looking orientation and having an inertially fixed spacecraft. To achieve this goal, we simulate a spacecraft in the low Earth orbit using gravitational and non-gravitational accelerations, and we develop an in-orbit performance model for Mach- Zehnder-type quantum accelerometers capable of calculating the detection noise, quantum projection noise, laser frequency noise, wavefront aberration bias, and contrast loss, together with external effects such as the impact of rotation, and gravity gradient for each individual measurement. Using this modeling and based on the propagated orbit, we simulate the measurements of a 3-axis quantum accelerometer along the orbit in two different scenarios: first, we assume the spacecraft to maintain a nadir-pointing orientation, and then we consider another scenario in which the spacecraft is assumed to be inertially- fixed. The results demonstrate that the nadir-pointing orientation introduces more noise, particularly in the along-track and radial directions, due to uncompensated rotation. However, in both the nadir-pointing and inertially fixed scenarios, quantum sensors still produce white noise, consistent with their drift-free measurement capabilities. Furthermore, the findings emphasize the critical role of sensor placement within the spacecraft. Positioning the quantum accelerometer along the main axis of rotation is optimal, as it reduces the impact of centrifugal forces and improves measurement accuracy. This is especially important for spacecraft in nadir-pointing orientations or during maneuvers. This research is the simulation and implementation of a low-Earth orbit, undertaken as a proof-of-concept. In the future, we implement this modeling for a trajectory from Earth to the Moon. We discuss the challenges, limitations, and potential solutions.
We demonstrate a hybrid accelerometer that benefits from the advantages of both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and long term stability. First, the use of a real time correction of the atom interferometer phase by the signal from the classical accelerometer enables to run it at best performance without any isolation platform. Second, a servo-lock of the DC component of the conventional sensor output signal by the atomic one realizes a hybrid sensor. This method paves the way for applications in geophysics and in inertial navigation as it overcomes the main limitation of atomic accelerometers, namely, the dead times between consecutive measurements.
Quantum sensing using atom interferometry possesses immense potential for application in gravimetry, inertial navigation and for gravitational wave detection, apart from carrying out tests of fundamental physics. Atom interferometry can be used to perform absolute inertial measurements with unprecedented long term stability, unlike classical sensors which are prone to drift and incur calibration errors. However, atom interferometers seldom achieve their fundamental sensitivity due to the coupling of ambient vibrations. It is the dominant noise source that not only impairs performance but also affects its operability. Ideal compensation of the effects due to vibration noise using a versatile accelerometer, while concurrently enabling miniaturized atom interferometer setups has not been pioneered. Such a compact hybrid quantum sensor will enable reliable operation with an enhanced performance in field applications, paving the way for robust atom interferometry beyond laboratory conditions. A novel optomechanical resonator has been designed, developed and successfully hybridized with an atom interferometer to suppress the effects of vibration noise, and the results are presented in this thesis. The optomechanical resonator’s inertial test mass is simultaneously used to create a continuous intracavity optical lattice to sense its displacement, and a pulsed optical lattice to manipulate the atoms. For the first time, a broadband accelerometer is seamlessly hybridized with an atom interferometer via mechanical resonator mediated coupling of the optical lattices to measure acceleration. This enables elimination of vibration induced measurement ambiguity in our atom interferometer with a well defined mechanical transfer function. Vibration noise correlation is demonstrated up to our prototype atom interferometer’s most sensitive operating mode of T = 6 ms using double Bragg diffraction, ultimately limited by its technical noise. The optomechanical resonator measures acceleration with a sensitivity down to 1.1×10−6 ms−2/ √Hz corresponding to a displacement sensitivity of 8.6 × 10−15 m/ √Hz. Substantial 1/f noise suppression due to the developed optical readout scheme enables a measurement bandwidth spanning from sub-hertz frequencies up to several kilohertz. Multiple versions of the optomechanical resonator with different characteristics were developed and hybridized with our atom interferometer. This paves the way for developing tailored optomechanical resonators for specific inertial sensing applications.