Photon antibunching and sub-Poissonian statistics from quantum jumps in one and two atoms

Antibunching and sub-Poissonian statistics of the 11-μm photon emission from the ${5d}^{10}{6p}^2{P}_{\frac{1}{2}}$ to ${5d}^6{6s}^2{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}$ transition in one and two trapped ${\mathrm{Hg}}^{+}$ ions have been inferred from the quantum jumps of the laser-induced fluorescence of the first resonance transition at 194 nm. Each downward step in fluorescence was assumed to mark the emission of an 11-μm photon. Signals from two ions were consistent with the assumption that quantum jumps in the two ions occurred independently. Mandel's $Q$ parameter was determined to be approximately -0.25 for one and two ions.