  Integration of solid state quantum emitters into nanophotonic circuits is a
critical step towards fully on-chip quantum photonic based technologies. Among
potential materials platforms, quantum emitters in hexagonal boron nitride have
emerged over the last years as viable candidate. While the fundamental physical
properties have been intensively studied over the last years, only few works
have focused on the emitter integration into photonic resonators. Yet, for a
potential quantum photonic material platform, the integration with nanophotonic
cavities is an important cornerstone, as it enables the deliberate tuning of
the spontaneous emission and the improved readout of distinct transitions for
that quantum emitter. In this work, we demonstrate the resonant tuning of an
integrated monolithic hBN quantum emitter in a photonic crystal cavity through
gas condensation at cryogenic temperature. We resonantly coupled the zero
phonon line of the emitter to a cavity mode and demonstrate emission
enhancement and lifetime reduction, with an estimation for the Purcell factor
of ~ 15.
