  Individual neutral atoms excited to Rydberg states are a promising platform
for quantum simulation and quantum information processing. However,
experimental progress to date has been limited by short coherence times and
relatively low gate fidelities associated with such Rydberg excitations. We
report progress towards high-fidelity quantum control of Rydberg atom qubits.
Enabled by a reduction in laser phase noise, our approach yields a significant
improvement in coherence properties of individual qubits. We further show that
this high-fidelity control extends to the multi-particle case by preparing a
two-atom entangled state with a fidelity exceeding 0.97(3), and extending its
lifetime with a two-atom dynamical decoupling protocol. These advances open up
new prospects for scalable quantum simulation and quantum computation with
neutral atoms.
