  Solid-state quantum emitters are garnering a lot of attention due to their
role in scalable quantum photonics. A notable majority of these emitters,
however, exhibit spectral diffusion due to local, fluctuating electromagnetic
fields. In this work, we demonstrate efficient Anti-Stokes (AS) excitation of
quantum emitters in hexagonal boron nitride (hBN), and show that the process
results in the suppression of a specific mechanism responsible for spectral
diffusion of the emitters. We also demonstrate an all-optical gating scheme
that exploits Stokes and Anti-Stokes excitation to manipulate spectral
diffusion so as to switch and lock the emission energy of the photon source. In
this scheme, reversible spectral jumps are deliberately enabled by pumping the
emitter with high energy (Stokes) excitation; AS excitation is then used to
lock the system into a fixed state characterized by a fixed emission energy.
Our results provide important insights into the photophysical properties of
quantum emitters in hBN, and introduce a new strategy for controlling the
emission wavelength of quantum emitters.
