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 quantum phase in an $N$-state Rydberg atom data register. The register was prepared as a wave packet with one state phase reversed from the others (the “marked bit”). A half-cycle pulse then drove a significant portion of the electron probability into the flipped state via multimode interference.