Abstract
Quantum Hall edge states offer avenues for quasiparticle interferometry, provided that the ratio between phase coherence length and quantum Hall interferometer (QHI) size is large enough. Maximizing this ratio by shrinking the QHI area favors Coulomb interactions, impairing clear interferences observation. Here, we use scanning gate spectroscopy to probe interference regime in antidots-based graphene nano-QHIs, free of localized states (LS). A simple Fabry-Perot model, without Coulomb interaction, reproduces the QHI phenomenology, even in the smallest QHI, highlighting the LS detrimental role.