Observation of quantum jumps in a single atom

Abstract

We detect the radiatively driven electric quadrupole transition to the metastable D522 state in a single, laser-cooled Hg II ion by monitoring the abrupt cessation of the fluorescence signal from the laser-excited S122†P122 first resonance line. When the ion "jumps" back from the metastable D state to the ground S state, the S†P resonance fluorescence signal immediately returns. The statistical properties of the quantum jumps are investigated; for example, photon antibunching in the emission from the D state is observed with 100% efficiency. © 1986 The American Physical Society.