Non-classical light 20 years later: an assessment of the voyage into Hilbert space

Although diverse manifestations of the quantum or non-classical character of the electromagnetic field have arisen over the past two decades in quantum optics, almost without exception these observations have been made in a domain of weak coupling for which dissipation is dominant over the coherent dynamical processes associated with single quanta. By contrast, research in the area of cavity quantum electrodynamics has achieved the exceptional circumstance of strong coupling for the interaction of individual atoms with the quantized field of a high-quality resonator. The research programs in the Quantum Optics Group at Caltech attempt to explore quantum dynamical processes in this domain of strong coupling, and include investigations of photon antibunching due to quantum-state reduction, of the implementation of quantum logic with single photons, of new avenues for quantum-state synthesis and of atomic centre-of-mass motion for single atoms falling one-by-one through the field of a high-finesse optical cavity.