Missions

The three postdoctoral research projects are part of the European EQUIP-G project and aim to: 1- use the gravimeter developed by the LTE to compare the instruments acquired as part of EQUIP-G, scheduled for 2029 2- participate in the characterisation, testing and monitoring of instruments acquired as part of EQUIP-G 3- participate in use cases planned as part of EQUIP-G 1- We have developed a state-of-the-art cold atom gravimeter (CAG). The measurement is based on atomic interferometry techniques using stimulated Raman transitions on free-falling 87Rb atoms. The phase shift of the atomic interferometer is proportional to g, the acceleration due to gravity, which we measure with a sensitivity greater than that of conventional absolute gravimeters (5.7ng/rac(Hz)) and with greater accuracy (2ng). The instrumental limitations have been identified and several improvements are being made to achieve the 10-10 range in terms of accuracy and stability.
The postdoctoral researcher will work with the team to develop, characterise and implement the various improvements until the instrument is back in operation and characterised. The instrument will then be compared with other instruments based on different technologies. One of these comparisons will take place as part of the Horizon Europe EQUIP-G project in 2029. 2- All instruments acquired as part of the EQUIP-G project will be received by the LTE team, which will test them in the laboratory and in field conditions before making them available to the various teams in the EQUIP-G consortium. These instruments will be monitored by the LTE team and their traceability ensured thanks to measurements carried out in our reference laboratory, where the instruments will return for comparisons. The postdoc will participate in the organisation of these comparisons: general preparation of the facilities, welcoming and accompanying visitors, measurements and analysis of results. 3- The instruments will be deployed in the field in various use cases in which the postdoctoral researcher will be involved.

Activités

1- The post-doc's work will consist of finalising the modification of the vacuum chamber to enable the use of a crossed dipole trap with a 50W laser at 1.1μm. This trap will also need to be built. The opening of the vacuum chamber has been used to install a rotating retro-reflection mirror for the Raman lasers. This will improve our control over the alignment of the lasers and compensate for Coriolis acceleration. In order to improve our control over the initial position of the atoms, new PMO collimators are being developed. These are connected to an innovative automated beam splitter system for controlling the power in each PMO beam. The postdoc will participate in the characterisation of these different assemblies. The ultimate goal is to further improve the evaluation of the effects of Coriolis acceleration and wavefront distortions by performing measurements at very low temperatures and with more atoms. To achieve this, the evaporation sequence will need to be optimised by increasing the trap's capture volume. However, the use of dense samples of ultra-cold atoms, possibly condensed, instead of a more diluted source cooled by lasers, has a disadvantage linked to the effect of interatomic interactions, which we will study. A fibre-optic bench designed to control the gravimeter will be delivered. The post-doctoral researcher will participate in its installation and evaluation. He will build an optical bench in free space between the fibre-optic bench and the fibres connected to the gravimeter. He will set up and optimise the automation of the fibre bench. The uncertainty assessment and the performance obtained with the gravimeter will finally be tested. The gravimeter will be moved to the reference laboratory at the LNE for the final comparison of the EQUIP-G gravimeters. 2- Each time an EQUIP-G project instrument is received, the post-doc will be involved in evaluating its performance and will test the instrument prior to its implementation in use cases. The post-doc will be particularly involved in the two comparisons of EQUIP-G instruments to be carried out in 2026 and 2029. These activities will be carried out at the reference laboratory at the LNE. 3- The final phase of testing will consist of using the instruments in a use case 100 km from the reference laboratory. The postdoctoral researcher will participate in these installations and follow-ups, thereby contributing to one of the project's first use cases, as well as another in Germany, where the instrument will need to be installed and retrieved approximately three months later.

Compétences

Candidate profile: PhD in atomic physics or equivalent field with a focus on experimentation. Experience in instrumentation and metrology would be appreciated. Proficiency in instrumentation-computer interfaces and programming necessary for automatic data acquisition and remote monitoring of measurement results. Programming languages used within the team: C, Python, etc. Experience in supervising students is desirable. Fluency in written and spoken English.

Résultats attendus et contrôles

The result will be verified by the participation of the atomic gravimeter with an uncertainty assessment and performance at the nano-g level, in the final comparison of EQUIP-G at the LNE reference laboratory in April 2029. The final comparison will be carried out using as many instruments as possible acquired by EQUIP-G. The post-doctoral researcher will have participated in testing and monitoring these instruments and will be thoroughly familiar with them. They will participate in the final comparison using these instruments and the CAG, which they will have brought up to the desired performance level: accuracy better than 10-9g and sensitivity of 10-10g over the long term.

Contexte de travail

The candidate will join the LTE's IA&CI team at the Paris Observatory. Studies on the CAG will be carried out under the supervision of Sébastien Merlet, head of the activity, and with the assistance of Franck Pereira dos Santos, head of the IA&CI team. Activities directly related to the EQUIP-G project will be carried out under the supervision of Sébastien Merlet, PI of the project, and with the assistance of Jean Lautier-Gaud, project manager. Regular meetings will be held at the LTE at the Paris Observatory. The postdoc will interact with the student currently working on a thesis on improving the gravimeter, as well as a fixed-term engineer currently being recruited who will work on the gravimetric reference site as part of EQUIP-G. The position is entirely dedicated to the EQUIP-G project, submitted in response to the Horizon Europe call for projects 'Developing and deploying a network of quantum gravimeters in Europe'. This project, led by the CNRS-LTE, is the first step in the implementation of the terrestrial segment of the pan-European quantum gravimetry infrastructure, which will be based around a shared instrumentation facility. Activities will mainly be carried out at the LTE at the Paris Observatory and at the LNE Trappes, where the gravimetric reference site is located. The position is in a sector subject to scientific and technical potential protection (PPST) and therefore, in accordance with regulations, requires your arrival to be authorised by the competent authority of the MESR, both for access to the Paris Observatory facilities and those of the LNE Trappes.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

Use of a 50W power laser.