  The use of semiconductor nanocrystals in scalable quantum technologies
requires characterization of the exciton coherence dynamics in an
\emph{ensemble} of electronically isolated crystals in which system-bath
interactions are nevertheless strong. In this communication, we identify
signatures of Fano-like interference between excitons and photocarriers in the
coherent two-dimensional photoluminescence excitation spectral lineshapes of
mixed lead-halide perovskite nanocrystals in dilute solution. Specifically, by
tuning the femtosecond-pulse spectrum, we show such interference in an
intermediate coupling regime, which is evident in the coherent lineshape when
simultaneously exciting the exciton and the free-carrier band at higher energy.
We conclude that this interference is an intrinsic effect that will be
consequential in the quantum dynamics of the system and will thus dictate
decoherence dynamics, with consequences in their application in quantum
technologies.
