Quantum cutting (QC) converts one absorbed high-energy photon into two lower-energy emissive excitations. Yb-doped halide-perovskite nanocrystals are particularly promising because the semiconductor host provides strong UV-visible absorption, while Yb^3+ emits near 980 nm, within the absorption range of silicon. Absolute photoluminescence quantum yields (PLQYs) above 100% have been reported for Yb:CsPb(Cl,Br)3 nanocrystals. However, these results remain difficult to reproduce, and the microscopic processes responsible for photon multiplication are still debated. State of the art: PLQY measures the average number of emitted photons per absorbed photon but does not establish whether two photons originate from the same absorption event. QC should instead produce temporally correlated photon pairs from Yb emission, leading to photon bunching, a peak in the second-order correlation function g(2)(𝜏), whereas conventional one-to-one downshifting ideally produces Poissonian photon statistics. Correlation measurements therefore provide an orthogonal observable to PLQY. Project: The student will establish and validate a near-infrared photon-correlation experiment. Hyperspectral PLQY imaging will provide spatially and spectrally resolved absolute PLQY maps. Joint interpretations will assess whether the observed Yb emission arises from photon multiplication or conventional one-to-one sensitisation.