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Early observations of macroscopic quantum jumps in single atoms



Wayne M. Itano, James C. Bergquist, David J. Wineland


The observation of intermittent fluorescence of a single atomic ion, a phenomenon better known as 'macroscopic quantum jumps,' was an important early scientific application of the three-dimensional rf quadrupole (Paul) trap. The prediction of the phenomenon by Cook and Kimble grew out of a proposal by Dehmelt for a sensitive optical double-resonance technique, called 'electron shelving.' The existence of the quantum jumps was viewed with skepticism by some in the quantum optics community, perhaps due to the failure of some conventional calculations, for example the solutions to the optical Bloch equations, to predict them. Quantum jumps were observed nearly simultaneously by three different experimental groups, all with single, isolated ions in Paul traps. Some slightly earlier observations of excessive fluctuations in the laser-induced fluorescence of a single Hg+ ion by a group at the National Institute of Standards and Technology, viewed in retrospect, were due to quantum jumps. This shows how discoveries can be missed if unanticipated observations are ignored rather than investigated. A fourth experiment, performed not with a single, trapped ion, but with neutral atoms transiently observed in an atomic beam, and published at about the same time as the other experiments, has been almost totally neglected.
International Journal of Mass Spectrometry


barium, history of science, mercury, Paul trap, quantum jumps, quantum optics


Itano, W. , Bergquist, J. and Wineland, D. (2015), Early observations of macroscopic quantum jumps in single atoms, International Journal of Mass Spectrometry, [online], (Accessed June 20, 2024)


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Created March 25, 2015, Updated June 2, 2021