Cassidy's group performs precision optical and microwave spectroscopy of positronium -- a purely leptonic electron-positron atom -- to test bound-state QED to high order and search for new physics, most recently a precision microwave measurement of the 2^3S1 to 2^3P2 fine-structure interval. The group is also developing slow, focused positronium beams toward a laboratory measurement of antimatter's gravitational free-fall, continuing UCL's 50-year history of positron physics.

Hori performs precision two-photon laser spectroscopy of antiprotonic helium and other exotic atoms (much of it carried out at CERN's Antiproton Decelerator), testing CPT symmetry and QED and constraining the antiproton-to-electron mass ratio.

François Nez (DR CNRS, LKB Hydrogen Spectroscopy) performs ultra-high precision hydrogen spectroscopy and QED tests. Research: (1) 1S–3S hydrogen/deuterium spectroscopy — continuous-wave laser, optical frequency comb via REFIMEVE network, theory comparison at ppt level; (2) muonic hydrogen/atom spectroscopy — CREMA collaboration at PSI; determines proton charge radius with record precision; (3) GRASIAN — gravitational quantum states of hydrogen atoms and neutrons; probing short-range forces beyond Standard Model. Primarily fundamental physics rather than sensing applications, but uses precision optical metrology infrastructure.