Antisite defect qubits in monolayer transition metal dichalcogenides*

Quantum bit as the heart of quantum information technology brings unprecedented capability of computation that is expected to transform science and society in unimaginable ways. Being atomically thin and amendable to external controls, two-dimensional (2D) materials offer a new paradigm for the realization of patterned qubit fabrication and operation at room temperature. Using high-throughput atomistic simulations and a symmetry-based hypothesis, we identify six neutral anion-antisite defects in transition metal dichalcogenide (TMD) monolayers that host a paramagnetic triplet ground state. Our in-depth analysis reveals the nature of optical transitions and triplet-singlet intersystem crossings in the qubit, which provides a complete cycle for initialization, manipulation and redout of the qubit. As an illustrative example, the operational principles of the antisite qubit in WS₂ are discussed in details. We also demonstrate that the antisite defect qubit system is stable against interlayer interactions in a multilayer structure for qubit isolation and protection in future defect-based devices. The key characters of host materials that give rise to defects with a triplet ground state are discussed, which suggests a feasible strategy for continued discovery of promising defect qubits in diverse classes of 2D materials. Our study opens a new pathway for creating scalable and controllable spin qubits in 2D TMDs.