First-principles investigation of optically active quantum defects in hexagonal boron nitride

Two-dimensional materials (TDMs) have been recently found to host a variety of quantum point defects [1] that are potentially useful for advancing quantum information science and technology. Among a growing suite of the TDMs, hexagonal boron nitride (h-BN) has emerged as a host of bright single-photon emitters (SPEs) and optically active spin qubits operating at room temperature. However, there are several challenges to be addressed for realizing h-BN-based quantum applications. In this talk, we summarize our recent efforts to predict and understand optically active quantum defects in h-BN using density functional theory (DFT) and cluster correlation expansion theory (CCE). In the first part of the talk, we discuss the property of SPEs in terms of their coupling behavior to lattice strain and how engineered lattice strain could be used to understand the structural and optical properties of SPEs. For spin qubits in h-BN, we discuss the issue of the short spin coherence time of the boron vacancy spin in h-BN in the presence of the intrinsic dense nuclear spin bath. To address these issues, we combine CCE and DFT to predict that the spin coherence time in h-BN can be significantly increased by six times larger than its intrinsic limit in natural h-BN by employing isotopic enrichment and strain engineering. Our results strengthened the potential of h-BN quantum spin defects as materials platforms to realize TDM-based quantum sensors and integrated quantum photonics.