Originally working in experimental particle physics, her interests shifted to observational cosmology through her participation in the Supernova Legacy Survey and Baryon Oscillation Spectroscopic Survey projects.
[2] Ruhlmann-Kleider earned a diplôme d'études approfondies in nuclear and particle physics through her studies at the École normale supérieure de jeunes filles, and in 1988 completed a doctorate through the University of Paris,[3] for research at CEA Paris-Saclay, with the dissertation Measurement of the strong running coupling constant from W and Z production (UA2 experiment) directed by André Roussarie.
She began work on the Supernova Legacy Survey in 2006, and since then has continued her research in observational cosmology.
[2] More recently, her work on the Baryon Oscillation Spectroscopic Survey has led to new insights into dark energy.
[7] Ruhlmann-Kleider received the Ordre des Palmes académiques in 2002, and the CNRS Silver Medal in 2003.