Dephasing of multiparticle Rydberg excitations for fast entanglement generation

An approach to fast entanglement generation based on Rydberg dephasing of collective excitations (spin-waves) in large, optically thick atomic ensembles is proposed. Long-range $1/r^3$ atomic interactions are induced by microwave mixing of opposite-parity Rydberg states. Required long coherence times are achieved via four-photon excitation and read-out of long wavelength spin-waves. The dephasing mechanism is shown to have favorable, approximately exponential, scaling for entanglement generation.