Abstract We present a reflective atom-interferometric approach to acceleration sensing, in which matter waves are coherently split and recombined solely through diffraction from nanostructured surfaces. Unlike light-pulse atom interferometers, the method is completely laser-free and operates on millisecond time scales, enabling compact and robust sensor architectures. Two readout strategies are explored: (i) the shift of the diffracted output angles, and (ii) the interferometric phase modulation generated by three successive reflections within the device. Using analytical models for diffraction from a moving lattice, we compute the sensitivity to lateral and normal accelerations. The interferometric mode exhibits a pronounced amplification of small velocity changes, reaching sensitivities as low as $$10^{-10}\,{\text {g}}$$ 10 - 10 g for slow atoms and large incidence angles. The response is intrinsically stronger for lateral than for normal accelerations due to the asymmetry of the diffraction paths. Comparisons with existing technologies show that the reflective interferometer fills a gap between MEMS-based accelerometers and large light-pulse atom interferometers, offering high sensitivity, continuous readout, and a fully passive beam-splitting mechanism. These results identify reflective interferometry as a promising platform for next-generation quantum accelerometers.
Abstract We present a reflective atom-interferometric approach to acceleration sensing, in which matter waves are coherently split and recombined solely through diffraction from nanostructured surfaces. Unlike light-pulse atom interferometers, the method is completely laser-free and operates on millisecond time scales, enabling compact and robust sensor architectures. Two readout strategies are explored: (i) the shift of the diffracted output angles, and (ii) the interferometric phase modulation generated by three successive reflections within the device. Using analytical models for diffraction from a moving lattice, we compute the sensitivity to lateral and normal accelerations. The interferometric mode exhibits a pronounced amplification of small velocity changes, reaching sensitivities as low as 10−10g 10 - 10 g for slow atoms and large incidence angles. The response is intrinsically stronger for lateral than for normal accelerations due to the asymmetry of the diffraction paths. Comparisons with existing technologies show that the reflective interferometer fills a gap between MEMS-based accelerometers and large light-pulse atom interferometers, offering high sensitivity, continuous readout, and a fully passive beam-splitting mechanism. These results identify reflective interferometry as a promising platform for next-generation quantum accelerometers.
Since the first demonstrations in 1991, atom interferometry has been a burgeoning field of research. The work done in this field is motivated by the potential sensitivity improvements that atom-based devices can have over the current state-of-the-art light- and MEMS-based devices. This dissertation presents a new and unique approach to atom interferometry in that we perform the basic interferometric sequence of splitting, propagation, reflection, reverse-propagation, and recombination with atoms trapped in a phase-modulated (shaken) optical lattice. In both simulation and experiment we demonstrate a one-dimensional shaken lattice interferometer configured as an accelerometer. The interferometry sequence is developed through the use of learning and optimal control algorithms that allow us to implement the desired state-to-state transformations and perform the desired operations, e.g. splitting and recombination of the atoms trapped in the lattice. This device has a sensitivity that scales as the square of the interrogation time and an ability to distinguish both the magnitude and sign of an applied acceleration signal. Furthermore we show that we can tailor the transfer function of the interferometer to be sensitive to a signal of interest, e.g. an AC signal of a given frequency. Finally, we explore the analytics of shaken lattice interferometry and offer some suggestions as to the future of this new technology.
The creation of a matter-wave interferometer can be achieved by loading Bose-Einstein condensed atoms into an optical lattice. By shaking the lattice via either phase or frequency modulation, the traditional steps of interferometry; splitting, propagating, reflecting, again propagating and then recombining the atomic wavefunction, can be implemented, allowing for the sensing of broad range of inertial signals. This approach is interesting, since the atoms can be supported against external forces and perturbations, and the system can be completely reconfigurable on-the-fly for a new design goal. We report on theoretical and experimental results in which atoms are cooled to degeneracy in a dipole trap and subsequently loaded into a multidimensional optical lattice. Shaking protocols for obtaining interferometry steps are derived via machine-design approaches consisting of machine learning and quantum optimal control. Experimental confirmation of the designed operation of a two-dimensional vector accelerometer is shown and its performance to applied accelerations measured. Both the direction and magnitude of the applied signal is varied and validation of both scenarios presented.
Inertial navigation systems are vital for modern society, be it on airplanes or in the context of autonomous mobility. On the other hand atom interferometers are exquisite measurement devices for inertia in fundamental physics and field applications, but are mostly limited to measuring one inertial observable. By utilizing time averaged optical potentials, the ultra-cold atomic ensemble input to the interferometer can be prepared in nearly arbitrary fashion. This results in a boost of preparation speed and number of atoms in the interferometer by increasing the size of the trap to match the size of the pre-cooled ensemble for optimal loading. Successive fast reduction of the extend of the trap leads to optimal evaporation efficiency and leads to increased sensitivity of the device, due to reduced cycle time of the experiment and increased atom number. Beyond this, the technique allows for new sensor geometries via the creation of multiple single wells, allowing for differential atom interferometry with numerous simultaneous interferometers. In this thesis, the first matter-wave analogue of a classical accelerometer array is implemented via the creation of a 3 × 3 array of Bose-Einstein condensates, consisting of 3 × 105 atoms and spanning a total area of 1.6 mm2 . Successive manipulation of the matter-waves with atom optics, coherently addressing the momentum states of the ensembles, allows for splitting, redirecting and readout pulses, realizing Mach-Zehnder type atom interferometers. Correlation of the nine 1D-acceleration measurements output by the interferometers yields measurements of linear acceleration, Euler- and centrifugal acceleration. The estimated sensitivity limits per shot are 6 × 10−5m s−2 for linear acceleration, 0.19 rad s − 2 for rotational acceleration and 203 mrad s−1 for rotation rate and are mainly limited due to the short free fall time of the ensembles, constrained by the atom optics light field. The correlation also allowed to determine the rotation center, being close to the retro reflection mirror of the atom optics light field. Crucial for the realization of this measurement was the implementation of time averaged potentials as stated above, facilitated through two 2D acousto-optical deflectors and a software defined radio, allowing for generating the required RF-signals. The techniques to simultaneously load and evaporate multiple ensembles into distinct traps from a single cloud of cold atoms and subsequently enlarge the spacing between the ensembles with adiabatic transport ramps are of highest interest for e.g. the Very Long Baseline Atom Interferometer facility in Hannover. Due to the correlated outputs systematic errors, such as wave front abberations, can be nullified. Furthermore the scheme can be extended to 3D matter-wave arrays, fulfilling all requirements necessary for an autonomous inertial measurement unit.
Matter-wave interferometry has enabled high precision measurements of inertial forces such as gravity and the Coriolis force. This is facilitated by the long-term stability of the physical properties of atoms and lasers. Recent experiments have demonstrated the operation of portable, robust sensors using atom interferometry. This has potential uses in the context of inertial navigation, where conventional devices suffer from long-term drifts due to bias instability. Furthermore, determining position via dead reckoning requires minimisation of dead time between measurements. This thesis presents the development of an atom interferometer for measuring horizontal accelerations. In this configuration, gravity induces motion across the laser wavefront, which constrains the tolerable level of wavefront distortions. Effective control of the experiment allows the interferometer to be operated at a rate of 4 Hz. A cold ensemble of 10^6 atoms in the same internal state is prepared in 150 ms. The interferometer operates using a sequence of three laser pulses separated by T= 25 ms to achieve sensitivity to horizontal accelerations. Combining this with a classical accelerometer provides a method of correcting for vibration-induced noise, as well as determining the interferometer fringe order. After an integration time of 40 s, the sensitivity to horizontal accelerations is better than 3^-6 m s^-2. Effects which limit this sensitivity are discussed.
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.
We present a mobile 3D accelerometer based on matter-wave interferometry, which is capable of measuring three orthogonal accelerations, each with respect to an independent inertial reference frame defined by the surface of a mirror. On each axis, we construct a hybrid quantum/classical accelerometer by using correlations between the atoms and a mechanical accelerometer attached to the back of each reference mirror. This system combines the large bandwidth and dynamic range of classical devices with the high sensitivity and accuracy of atom interferometers. By correcting each classical accelerometer independently, we are able to track the full acceleration vector with high accuracy.