State-selective fluorescence detection
= State-selective fluorescence detection
A readout in which one logical <quantum state> is coupled to an optical cycling transition and scatters many <photons>, while another is dark. An ideal bright/dark record implements a <projective measurement> in the logical basis. Neglecting that record removes their relative <quantum coherence>. Missed photons, off-resonant excitation and pumping out of the logical subspace qualify the ideal model.