Quantum phase retrieval of a Rydberg wave packet using a half-cycle pulse

A terahertz half-cycle pulse was used to retrieve information stored as qua ntum phase in an N-state Rydberg atom data register. The register was prepa red as a wave packet with one state phase reversed from the others (the "ma rked bit"). A half-cycle pulse then drove a significant portion of the elec tron probability into the flipped state via multimode interference.