Deterministic coupling of site-controlled quantum emitters in monolayer semiconductors to plasmonic nanocavities

Solid-state single-quantum emitters are a crucial resource for on-chip photonic quantum technologies and require efficient cavity-emitter coupling to realize quantum networks beyond the single-node level. Previous approaches to enhance light-matter interactions rely on forming nanocavities around randomly located quantum dots or color centers but lack spatial control of the quantum emitter itself that is required for scaling. Here we demonstrate a deterministic approach to achieve Purcell-enhancement at lithographically defined locations using the sharp corner of a metal nanocube for both electric field enhancement and to deform a two-dimensional material. For a 3 by 4 array of strain-induced exciton quantum emitters formed into monolayer WSe2 we show spontaneous emission rate enhancement with Purcell-factors (FP) up to FP=1050 (average FP=272), single-photon purification, and cavity-enhanced quantum yields increasing from initially 1 % to 15 %. The utility of our nanoplasmonic platform is applicable to other 2D material, including boron nitride, opening new inroads in quantum photonics.