Graphene is promising material for high quality nano-resonators with low mass and high quality factor [1,2]. These properties make graphene resonators suitable candidates for studying a mechanical system in the quantum regime and to explore effects such as Casimir forces [3]. However, the readout of a mechanical quantum state requires a non-invasive measurement method. To this end, one approach is to use a quantum transducer to indirectly measure the motion of the mechanical system as is the case in hybrid systems [4].

We report on our recent progress in the study of single Dibenzoterrylene (DBT) molecules as single photon sources and nanoscale probes. We consider DBT molecules embedded in thin anthracene films, a system that allows stable single photon emission both at room and at cryogenic temperatures. We investigate the most important optical properties of the DBT:anthracene system as a whole. We then perform a full statistical study of the coupling between single DBT molecules by measuring the lifetimes of DBT both in the coupled and in the uncoupled case. The experimental results are framed into a simple universal scaling model, where the magnitude of coupling depends solely on universal parameters and on the distance d between the single emitter and the graphene monolayer. We apply this model to infer d and provide a proof of principle for a position ruler at the nanoscale [1].

In this study we lay the groundwork for a graphene-based fundamental ruler at the nanoscale. It relies on the efficient energy-transfer mechanism between single quantum emitters and low-doped graphene monolayers. Our experiments, conducted with dibenzoterrylene (DBT) molecules, allow going beyond ensemble analysis due to the emitter photo-stability and brightness. A quantitative characterization of the fluorescence decay-rate modification is presented and compared to a simple model, showing agreement with the $d^{-4}$ dependence, a genuine manifestation of a dipole interacting with a 2D material. With DBT molecules, we can estimate a potential uncertainty in position measurements as low as 5nm in the range below 30nm.