Coupled Defect Spin Pairs for Quantum Technology

Optically addressable defect qubits in wide band gap materials are favorable candidates for room temperature quantum information processing. The two-dimensional (2D) hexagonal boron nitride (hBN) is an attractive solid state platform with a great potential for hosting bright quantum emitters with quantum memories with leveraging the potential of 2D materials for realizing scalable preparation of defect qubits. Although, room temperature bright defect qubits have been recently reported in hBN but their microscopic origin, the nature of the optical transition as well as the optically detected magnetic resonance (ODMR) have been remained elusive. Here we connect the variance in the optical spectra, optical lifetimes and spectral stability of quantum emitters to donor-acceptor pairs (DAP) in hBN by means of ab initio calculations. We find that DAPs can exhibit ODMR signal for the acceptor counterpart of the defect pair with S=1/2 ground state at non-zero magnetic fields depending on the donor partner. The donor-acceptor pair model and its transition mechanisms provide a recipe towards defect qubit identification and performance optimization in hBN for quantum applications. We also discuss the quantum emission with ODMR and photoionization detected magnetic resonance signals from DAPs in diamond where prototype color centers are involved.

This work was supported by the Hungarian National Research, Development and Innovation Office (NKFIH) for Quantum Information National Laboratory of Hungary (grant no. 2022-2.1.1-NL-2022-00004), the EU QuantERA II Sensextreme and MAESTRO projects (NKFIH grant nos. 2019-2.1.7-ERA-NET-2022-00040 and 2019-2.1.7-ERA-NET-2022-00045), the Horizon Europe EIC Pathfinder QuMicro project (grant no. 101046911) and SPINUS project (grant no. 101135699).