  Dipolar quantum droplets are exotic quantum objects that are self-bound due
to the subtle balance of attraction, repulsion and quantum correlations. Here
we present a systematic study of the critical atom number of these self-bound
droplets, comparing the experimental results with extended mean-field
Gross-Pitaevskii equation (eGPE) and quantum Monte-Carlo simulations of the
dilute system. The respective theoretical predictions differ, questioning the
validity of the current theoretical state-of-the-art description of quantum
droplets within the eGPE framework and indicating that correlations in the
system are significant. Furthermore, we show that our system can serve as a
sensitive testing ground for many-body theories in the near future.
