title: Coherence and Rydberg Blockade of Atomic Ensemble Qubits.
abstract: We demonstrate |W⟩ state encoding of multiatom ensemble qubits. Using optically trapped Rb atoms, the T_{2} coherence time is 2.6(3) ms for N[over ¯]=7.6 atoms and scales approximately inversely with the number of atoms. Strong Rydberg blockade between two ensemble qubits is demonstrated with a fidelity of 0.89(1), and with a fidelity of ∼1.0 when postselected on a control ensemble excitation. These results are a significant step towards deterministic entanglement of atomic ensembles.
authors.affiliation: Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: M
authors.initials: M
authors.lastname: Ebert
authors.affiliation: Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: M
authors.initials: M
authors.lastname: Kwon
authors.affiliation: Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: T G
authors.initials: TG
authors.lastname: Walker
authors.affiliation: Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: M
authors.initials: M
authors.lastname: Saffman