Gleyzes is a CNRS researcher in the Rydberg Atoms team at LKB (successor to Serge Haroche's cavity-QED group), where he achieved the first quantum non-demolition detection of a single microwave photon. The team now prepares non-classical states of circular Rydberg atoms as probes for electric- and magnetic-field sensing below the standard quantum limit, uses quantum optimal control to navigate large Rydberg Hilbert spaces, and has demonstrated millisecond-lived circular states at room temperature, a route toward practical Rydberg-atom quantum sensors and simulators.