Stochastic Cooling of a Trapped Ion by Null Detection of Its Fluorescence

When a single trapped ion is laser excited to a metastable state, its “quantum jump” inhibits the laser-excited light scattering on a resonance line. This event, and its inverse, modifies the distribution over the oscillator levels $\left(n\right)$ of the ion's vibration in the trap. In particular, unsuccessful attempts to deexcite on vibrational sidebands decrease $〈n〉$ to sub-Doppler values and may leave the ion in a “trapped” Fock state decoupled from the light.