Fast Preparation and Detection of a Rydberg Qubit Using Atomic Ensembles

We demonstrate a new approach for fast preparation, manipulation, and collective readout of an atomic Rydberg-state qubit. By making use of Rydberg blockade inside a small atomic ensemble, we prepare a single qubit within 3 mu s with a success probability of F-p = 0.93 +/- 0.02, rotate it, and read out its state in 6 mu s with a single-shot fidelity of F-d = 0.92 +/- 0.04. The ensemble-assisted detection is 10(3) times faster than imaging of a single atom with the same optical resolution, and enables fast repeated nondestructive measurement. We observe qubit coherence times of 15 mu s, much longer than the pi rotation time of 90 ns. Potential applications ranging from faster quantum information processing in atom arrays to efficient implementation of quantum error correction are discussed.