  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.
