Entanglement experiments with single atoms and photons in a cavity

Summary form only given. We perform experiments in which atoms interact one at a time with a few photons in a cavity. Entanglement between atoms and photons is produced under well controlled conditions, leading to textbook demonstrations of basic quantum concepts. Among recent experiments performed at ENS, we will focus on an ideal nondestructive detection of a single photon which amounts to the operation of a quantum logic gate. We will also describe a three atom experiment in which we demonstrate correlations of the type first discussed by Greenberger, Horne and Zeilinger. The extension of these experiments to larger atom and photon numbers is a challenging task which involves a difficult fight against decoherence. Improving on the quality factor of our cavity as well as on various other aspects of our experimental set-up, we plan to keep increasing progressively the number of particles (atoms or photons) we are juggling coherently with. We will thus study more and more complex entangled systems and pursue in this way our exploration of the elusive quantum classical boundary.