Recent technological advancements in atom interferometry have demonstrated extremely precise inertial measurements of acceleration and rotation. These could be used to develop ultra-precise inertial navigation systems that approach GPS navigation. The paper presents a rudimentary exposition of the interferometer which is based on beams of atoms cooled by lasers to a velocity of the order of 1 m/s and launched along two trajectories that re-combine, as in a classical interferometer. Using the dual wave-particle quantum mechanical properties of atoms, the differential phase of the interfering beams is indicative of inertial acceleration and rotation, similar to the Sagnac effect. Due to the much shorter wavelength of the atomic beam, the sensitivity is many orders of magnitude greater. Concluding analyses show that an inertial navigation system with 5/hr drift is technically possible.
Recent technological advancements in atom interferometry have demonstrated extremely precise inertial measurements of acceleration and rotation. These could be used to develop ultra-precise inertial navigation systems that approach GPS navigation. The paper presents a rudimentary exposition of the interferometer which is based on beams of atoms cooled by lasers to a velocity of the order of 1 m/s and launched along two trajectories that re-combine, as in a classical interferometer. Using the dual wave-particle quantum mechanical properties of atoms, the differential phase of the interfering beams is indicative of inertial acceleration and rotation, similar to the Sagnac effect. Due to the much shorter wavelength of the atomic beam, the sensitivity is many orders of magnitude greater. Concluding analyses show that an inertial navigation system with 5/hr drift is technically possible.
The recent development of the atom interferometer and its demonstration as an inertial sensor of acceleration and rotation rate augur a new generation of inertial navigation systems that would rival today's satellite navigation accuracy at the few-meter level. This paper reviews the principles of inertial measurement using the atom interferometer from a rudimentary viewpoint to illustrate the fundamentals and to highlight some of the potential shortcomings with a particular type, the cold-atom interferometer. One of these shortcomings is the fact that this interferometer requires a finite period of time during which the atoms are prepared (cooled) before they enter the interferometer and respond to its dynamics relative to an inertial frame. This lapse in the measurement duty cycle could be supplemented with very precise conventional inertial measurement units (IMUs), or eliminated with multiple, interleaved atom interferometers. Error analyses show that cold-atom interferometric IMUs that capture 50 percent of the dynamics must be coupled with conventional IMUs that are 50 times more accurate than typical navigation-grade units to sustain a horizontal position error of under 5 m (root mean square) after 1 h.
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.
Inertial sensors based on cold atom interferometry exhibit many interesting features for applications related to inertial navigation, particularly in terms of sensitivity and long-term stability. However, at present the typical atom interferometer is still very much an experiment—consisting of a bulky, static apparatus with a limited dynamic range and high sensitivity to environmental effects. To be compliant with mobile applications further development is needed. In this work, we present a compact and mobile experiment, which we recently used to achieve the first inertial measurements with an atomic accelerometer onboard an aircraft. By integrating classical inertial sensors into our apparatus, we are able to operate the atomic sensor well beyond its standard operating range, corresponding to half of an interference fringe. We report atom-based acceleration measurements along both the horizontal and vertical axes of the aircraft with one-shot sensitivities of 2.3 × 10−4 g over a range of ∼ 0.1 g. The same technology can be used to develop cold-atom gyroscopes, which could surpass the best optical gyroscopes in terms of long-term sensitivity. Our apparatus was also designed to study multi-axis atom interferometry with the goal of realizing a full inertial measurement unit comprised of the three axes of acceleration and rotation. Finally, we present a compact and tunable laser system, which constitutes an essential part of any cold-atom-based sensor. The architecture of the laser is based on phase modulating a single fiber-optic laser diode, and can be tuned over a range of 1 GHz in less than 200 μs.
In this paper,we described the progress of cold atom gyroscope.We launched the atoms along the same trajectory accurately and the opposite direction by controlling the frequency of directed digital system circuit.Using stimulated Raman beams,we operated the cold atoms and realized the atom interferometer fringes.With this configuration,it will greatly eliminate the common mode noise caused by uncertainty factor,such as the phase of the Raman laser beams,the gravity acceleration.It will significantly improve the precision in our experiment.The atom gyroscope will give a new way for the inertial navigation technology in the future.
Quantum technology became a new tool for navigation based on measuring accelerations and rotations. However, the full potential of atom interferometers that operate with ultracold atoms has not yet been exploited. This paper presents current developments in the field of generation and application of Bose–Einstein condensates for inertial navigation. It covers the advancements in the form of atom chip and compact vacuum technology, classical sensor hybridization, and a multi-axis atom interferometry technique. In addition, the synergies of combining quantum sensors with classical inertial measurement units and their implications for navigation trajectories 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.