Lifetime limited and tunable quantum emitters in hexagonal boron nitride

Color centers in hexagonal boron nitride (h-BN) are bright stable sources of quantum light in the visible range of the spectrum. Spectral broadening mechanisms such as spectral diffusion have limited the application of these emitters in many quantum communication technologies as it prevents the emitters to reach their fundamental Fourier transform limit. Here we report tunable nearly lifetime limited single photon emitters in h-BN located in a fully Van der Waals device consisting of Graphene and h-BN. We suppress spectral diffusion by applying an electrostatic field at cryogenic temperature of 6.5K, The linewidth measured via photoluminescence excitation shows two orders of magnitude reduction from 8.5 GHz down to 89 MHz. Furthermore, we show Stark tunability of 2.7meV/(V/nm) over a range of 400 GHz. Our findings can be utilized for on-chip quantum technologies based on h-BN emitters.