We present an efficient method for producing N particle entangled states using Rydberg blockade interactions. Optical excitation of Rydberg states that interact weakly, yet have a strong coupling to a second control state is used to achieve state dependent qubit rotations in small ensembles. On the basis of quantitative calculations we predict that an N=8 Schr\"odinger cat state can be produced with a fidelity of 84% in cold Rb atoms.
@article{arxiv.0812.2425,
title = {Efficient multiparticle entanglement via asymmetric Rydberg blockade},
author = {M. Saffman and K. Molmer},
journal= {arXiv preprint arXiv:0812.2425},
year = {2010}
}