Combes is a theorist of continuous quantum measurement, quantum trajectories, quantum-limited amplification and quantum filtering, with a strong record of working directly alongside superconducting-circuit and optical experiments rather than in isolation. Recent directions include the fundamental limits of amplifier-based sensing, error-corrected and adaptive metrology protocols, and characterisation/verification of noisy quantum devices. Positioned against the established body of NV-ensemble quantum sensing work — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — his work supplies the estimation-theoretic scaffolding — quantum Fisher information, back-action limits, adaptive protocols — that determines whether an NV ensemble running DEER or nanoscale NMR at pT/sqrt(Hz) is actually operating at its fundamental bound or leaving sensitivity on the table. Theory PI, but explicitly experiment-facing.