TOwards the New generation of atomIC sensorS – TONICS

Atom interferometry is a technology that allows measurements to be performed with extreme precision and accuracy. It has been applied to the measurement of several physical quantities, covering inertial quantities, atomic polarizations and fundamental physical constants, such as the Newtonian gravitational constant G and the fine structure constant a. For the next decade, research in atomic interferometry has set itself major challenges such as the detection of gravitational waves in a frequency range inaccessible to optical interferometers. For that a gain in sensitivity of 3 to 4 orders of magnitude compared to the state of the art is required.
The TONICS project aims at bringing together the competences of two teams from LKB and SYRTE to overcome the limits to the accuracy and sensitivity of atomic interferometers. In particular, the effects related to the distortion of the intensity profile of the laser beams. We will work jointly to implement reliable and robust methods to improve the accuracy of our state-of-the-art gravity and atomic recoil measurements. This step is essential to exploit and validate the benefit of novel methods advocated to realize ultra sensitive interferometers, such as large momentum atomic beam splitters (LMT) at high orders and quantum engineering protocols such as spin compression to surpass the standard quantum limit.

The TONICS project is based on three parts.
1/ The development of new robust experimental tools to reduce and control the effect of optical aberrations. For this, the SYRTE team will work on designing collimators with high optical quality and the LKB team will study different laser cooling schemes to provide an experimental protocol for producing a dense source of ultra-cold atoms in a cycle time of the order of a second. In parallel, we will work on the improvement of our two experimental set-ups to improve their sensitivity to exploit fully the benefits of these two ingredients.

2/ The development of a common library for the numerical modeling and simulation of the physical mechanisms at the origin of the systematic effects that limit the accuracy of our measurements. This will require cross-testing of both experiments and will allow a reliable evaluation of the systematic biases. This sequence of work will require very frequent exchanges which will probably be facilitated by the recruitment of a common PhD student and the creation of a common website.

3/ Optimization of the coherence of the large momentum beam splitters based on a combination of the double Raman diffraction technique developed by the SYRTE team and the Bloch oscillation technique in an accelerated optical lattice, which remain the area of expertise of the LKB team. The study of a symmetric atomic interferometer using these LMTs will enable us to evaluate its performance. Our objective is to demonstrate a contrast higher than 30% with a separation of 200 hk.

We are aiming at performances that surpass the state of the art. The goal of the SYRTE team is an absolute gravity measurement with an accuracy of less than 10-8 m.s-2 and a long-term stability better than 10-10 m.s-2. A continuous, absolute gravity meter with long-term stability of this level will meet the needs of the geophysical community that are not covered by existing technologies. The objective of the LKB team is to measure the recoil velocity of the two rubidium isotopes with a relative uncertainty of a few 10-11. This should validate the recent determination of the fine-structure constant and/or will explain the significant discrepancy with the value deduced from the Cs recoil measurement.

This level of uncertainty is also required to be able to observe on the electron, a possible effect that could be behind the persistent discrepancy between the theoretical and experimental values of the muon's magnetic moment anomalous.