John Rarity's group works on quantum-enhanced measurements and free-space quantum key distribution. Research: (1) quantum imaging with undetected photons — mid-infrared gas sensing (CO2, CH4) exploiting entangled photon pairs, with only near-IR photons detected (startup QLM); (2) sub-shot-noise imaging using quantum-identical photon beams; (3) spin-photon interfaces (1D cavity with near-unit scattering efficiency); (4) compact satellite QKD transmitters (EPSRC Quantum Comms Hub). Highly relevant to quantum-enhanced sensing.