  Two-electron charged self-assembled quantum dot molecules exhibit a
decoherence-avoiding singlet-triplet qubit subspace and an efficient
spin-photon interface. Here, we demonstrate that the cycling transitions
originating from auxiliary ground states in the same system allow for an
efficient optical read-out of a singlet-triplet qubit. By implementing a
spin-selective state transfer to the auxiliary state using a resonant laser
field, we observe an improvement approaching two orders of magnitude in
fidelity as compared to spin measurement by light scattering directly from the
qubit states. Embedding the quantum dot molecule inside a low quality-factor
micro-cavity structure should enable single-shot qubit read-out.
