Shelved optical electron amplifier: observation of quantum jumps

The direct observation of quantum jumps between the 6(2)S1/2 state and the 5(2)D5/2 state of an individual laser-cooled Ba(+) ion contained in a radio- frequency trap is reported. The state detection and cooling are performed by two lasers which cause 6(2)S1/2-6(2)P1/2-5(2)D3/2 transitions. Incoherent excitation to the 5(2)D5/2 state (via the 6(2)P3/2 level) causes the fluorescence from the 6(2)P1/2 state to be suppressed for the more than 30-sec lifetime of that state, after which the fluorescence reappears. The resulting 'telegraph signal' provides a direct monitor of the atomic state. (Author)