  We demonstrate $|W\rangle$ state encoding of multi-atom ensemble qubits.
Using optically trapped Rb atoms the $T_2$ coherence time is 2.6(3) ms for
$\bar N=7.6$ 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 a fidelity of $\sim \hspace{-.05cm}1.0$ when
postselected on control ensemble excitation. These results are a significant
step towards deterministic entanglement of atomic ensembles.

Quantum Physics;Atomic Physics