| Dipole-dipole interactions are ubiquitous in cold gases of Rydberg atoms. Even at the relatively low densities of atoms held in a magneto-opticaltrap the dipole-dipole interactions are often larger in magnitude than the kinetic energies of the atoms, and on the time scale of typical experiemnts the essentially frozen gas can resemble an amorphous solid. Not surprisingly dipole-dipole interactions between cold Rydberg atoms have been proposed as the basis of quantum gates. Both many body and binary dipole-dipole interactions among or between Rydberg atoms have been observed experimentally, and these will be the focus of this talk. Several manifestations of many body effects have been observed in resonant dipole-dipole energy transfer by very different techniques, and near resonant binary dipole-dipole interactions lead to ionizing collisions which can easily convert the cold Rydberg gas into a plasma. The latter observation suggests that, to be useful, samples of Rydberg Atoms will have to be regular, perhaps on some sort of lattice. |
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