  Perovskite quantum dots (PQDs) provide a robust solution-based approach to
efficient solar cells, bright light-emitting devices, and quantum sources of
light. Quantifying heterogeneity and understanding coupling between dots is
critical for these applications. We use double-nanohole optical trapping to
size individual dots and correlate to emission energy shifts from quantum
confinement. We were able to assemble a second dot in the trap, which allows us
to observe the coupling between dots. We observe a systematic red-shift of 1.1
$\pm$ 0.6 meV in the emission wavelength. Theoretical analysis shows that the
observed shift is consistent with resonant energy transfer and is unusually
large due to moderate-to-large quantum confinement in PQDs. This demonstrates
the promise of PQDs for entanglement in quantum information applications. This
work enables future in situ control of PQD growth as well as studies of the
coupling between small PQD assemblies with quantum information applications in
mind.
