  In the famous quantum communication scheme developed by Duan {\it et
al.}[L.M. Duan, M.D. Lukin, J.I. Cirac, and P. Zoller, Nature (London) {\bf
414} 413 (2001)], the probability of successful generating a symmetric
collective atomic state with a single-photon emitted have to be far smaller
than 1 to obtain an acceptable entangled state. Because of strong dipole-dipole
interaction between two Rydberg atoms, more than one simultaneous excitations
in an atomic ensembles are greatly suppressed, which makes it possible to
excite a mesoscopic cold atomic ensemble into a singly-excited symmetric
collective state accompanied by a signal photon with near unity success
probability, at the same higher-order excitations can be significantly
inhibited.
