Coherence Properties of Electron-Beam-Activated Emitters in Hexagonal Boron Nitride under Resonant Excitation

Two-dimensional (2D) materials are becoming increasingly popular as a platform for studies of quantum phenomena and for the production of prototype quantum technologies. Quantum emitters in 2D materials can host two-level systems that can act as qubits for quantum information processing. Here, we characterize the behavior of position-controlled quantum emitters in hexagonal boron nitride at cryogenic temperatures. Over two dozen sites, we observe an ultranarrow distribution of the zero phonon line at approximately 436 nm, together with strong linearly polarized emission. We employ resonant excitation to characterize the emission lineshape and find spectral diffusion and phonon broadening contribute to linewidths in the range 1-2 GHz. Rabi oscillations are observed at a range of resonant excitation powers, and under 1-μW excitation a coherent superposition is maintained up to 0.90 ns. Our results are promising for future employment of quantum emitters in h-BN for scalable quantum technologies.