Theory in support of precision measurements : from super resolution to new-physics searches. – (Alexander Boeschoten/ LCAR / Seminar). – 18/12/2025, 11H

Séminaire LCAR

Alexander Boeschoten, Laboratoire Kastler Brossel, Sorbonne Université, ENS-Université PSL, CNRS, Collège de France

Résumé : Achieving ever higher precision and accuracy in measurements is essential in many fields of physics. It leads to both technological innovation — for example in quantum-enhanced sensing — as well as to a better fundamental understanding of nature by testing the Standard Model of particle physics. Realizing and interpreting such precision experiments requires a close interplay between experiment and theory.
In this talk, I will discuss how theory is essential in the design, performance, and interpretation of precision experiments.
First, I will explain how quantum theory can be used to find the ultimate precision limits achievable in a measurement. In particular, I will present a general framework to calculate the Quantum Fisher information matrix for any parameter which is encoded in the modal part of light [1]. This matrix provides clear criteria for optimal joint estimations, and can be used to benchmark experimental multi-parameter estimations and find optimal measurement strategies by carefully shaping the modes and populating them with non-classical light.
Second, I will discuss how accurate theoretical modelling is essential for both performing and interpreting precision measurements searching for new-physics at low energy . When probing fundamental parameters or interactions, the measurement cannot be calibrated and we must instead rely on an accurate theoretical description of the system in its environment and of the measurement process itself. I will illustrate this by discussing a novel measurement method for searching for the electron electric dipole moment in BaF [2], which reduces systematic biases and the number of auxiliary measurements.

[1] Boeschoten, A., Sorelli, G., Gessner, M., Fabre, C., & Treps, N. (2025). Estimation of multiple parameters encoded in the modal structure of light. arXiv:2505.16435.
[2] Boeschoten, A., Marshall, V. R., Meijknecht, T. B., Touwen, A. P., … & NL-eEDM Collaboration. (2024). Spin-precession method for sensitive electric dipole moment searches. Physical Review A, 110(1), L010801.