Quantum beats in continuously excited atomic cascades

http://www.phys.ens.fr/~dalibard/publi3/Optcom\₈4.pdfInternational audienceWe report on the observation of strong Zeeman beats in the temporal correlation between the two photons emitted in the 4p21 S0 → 4s 4p 1 P1 → 4s21 S0 cascade in calcium. These beats result from a quantum interference between the various decaying channels. Unlike usual quantum beats, they are observed with a continuous excitation of the upper level