TRANSIENT INTERNAL DYNAMICS OF A MULTILEVEL ION

The autocorrelation g((2))(tau) of the photon-counting signal from las er-induced light scattering off a single trapped and laser-cooled Baion shows dramatic nonclassical effects: g((2))(tau) increasing upon d elay tau close to zero (''antibunching'') is accompanied (i) by its ex treme peak values, (ii) by long transients and long appearance of subu nity values (''sub-Poissonian light''), both extending much beyond the lifetime of the ion's resonance level, and (iii) by modulation from m agnetic precession, as is common with quantum beats. These phenomena h ighlight the internal multilevel structure of the ion, hint at optical pumping, and prove the coherent evolution of the ion's internal state . The preparation of the ion in a coherent superposition by spontaneou s decay is demonstrated. The counting variance of the scattered light, measured in terms of Mandel's Q parameter, deviates from that of clas sical light by up to Delta Q = -7 X 10(-4).