Miniaturized Multi-axis Quantum Sensors – MiniXQuanta

To design the grating accelerometer, we will first simulate the configuration of interrogation beams expected to be produced from the grating. We call this the Delta configuration. It will allow us to validate the principle of selecting different axes using velocity-sensitive Raman transitions, and it will give us the freedom to study the influence of different parameters (e.g. quantization axis, beam polarization, intensity ratio) in this complex architecture. This study will help define the specifications required for the design of the chip.
In parallel, we will tackle the engineering challenge of miniaturizing this technology. Following the development of specialized hybrid atom chips, the development of a miniaturized three-axis accelerometer constitutes the central part of the study and involves all the project partners. Our industrial partner (iXblue) will provide additional specifications for real-world use, such as the maximum size, weight and power of the device. Finally, the performance of the miniaturized sensor will be evaluated, and we will define a roadmap for future improvements.
Ultra-cold atoms are essential to improving the performance of these devices, especially for the simultaneous interrogation techniques. Hence, the project also involves the development of a miniaturized ultra-cold atom source. The gain of ultra-cold atoms compared to cold atoms will be evaluated at the end of the project.

Development of the grating:

The choice of the grating geometry is based on numerical simulations using the Fourier modal method and the set up of optical specifications for laser cooling in a tetrahedral configuration.

Development of the hybrid chip:

The magnetic chip is achieved. This magnetic chip supplies a trap centered at a distance of 500µm from the surface of the wires with a trap frequency ~500Hz for a current lower than 10 A. First tests of hybridization of the chip including a macroscopic Z wire have been done.

Interferometry on chip :

Simulations have been done to determine the different possible transitions in a interferometer on chip. A report summarizing the results have been provided. The issue to address specifically the required Raman transitions for a three-axis interferometer is tackled. The two solutions currently considered to solve this problem are the degeneracy removal of the different transitions using Doppler effect, obtained by giving to the atoms a specific direction and norm of the vector velocity on one hand, and a selective illumination of the grating during the interferometers reducing the number of diffracted beams on the other hand.

Our project will lead to several innovative outcomes:
Simultaneous measurements of the different components of the acceleration and rotation vectors using a single source of atoms.
Thanks to the grating, a high level of stability of axis alignment, which is critical for navigation.
A miniaturized CAI sensor head with a total volume of ~100 cm3.
An ultra-cold atom source increasing the contrast of the atom interferometer and thus allowing better performance for applications which require high sensitivity.
New types of cold-atom gyroscopes (CAGs) that are insensitive to spurious accelerations and initial velocities—the two limiting effects in existing devices.

1. Optique Nice 2022 session PAMO, Romain Calviac, Source atomique ultra-froide sur puce pour des applications embarquées (07/07/2022)
2. Workshop iQlev S.templier Cold atom 3-axis accelerometer for inertial navigation (22/11/2021)
3. Workshop Space optic for geophysics B. Battelier (Atom) optics in Space (11/10/2021)

Most atomic sensor measurements are one-dimensional, meaning they can measure only a single axis of rotation or acceleration at a time. For inertial navigation, reconstructing the trajectory of a moving body requires simultaneous measurements of accelerations and rotations along three mutually orthogonal directions—the basis of a full inertial measurement unit (IMU). The primary goal of this project is to advance quantum technology toward an IMU, by realizing a miniaturized cold-atom interferometer that is capable of measuring the full three-dimensional acceleration and rotation vectors. Our plan is to realize the first multi-axis interferometer with ultra-cold atoms on a hybrid magneto-grating chip. The goal of MiniXQuanta is to drive the development of high-performance miniature quantum inertial sensors to the highest performance level (strategic grade) for navigation. This ambitious goal would make long-term GPS-free navigation a reality.