Electrically controlled charge qubit in van der Waals heterostructures: From ab initio calculation to tight-binding models

Quantum computing demands innovative approaches for realizing qubits, and one promising avenue involves leveraging gated hybridized van der Waals (vdW) vertical heterostructures, referred to as vdW qubits. The two-level system that characterizes the vdW qubit comes from the layer-dependent orbital character of the charge carrier. This paper investigates the potential of gated vdW heterostructures for quantum computing. We study how gate fields affect the orbital composition of bands, enabling spatial superposition of electrons across layers of two-dimensional materials. Our ab initio calculations assess 20 transition metal dichalcogenides, identifying layers with slight energy offsets as vdW qubit candidates. Our investigation extends to the heterostructures formed based on the layered materials meeting these criteria. To simulate these qubits within large quantum circuits efficiently, we employ the tight-binding approach with maximally localized Wannier functions, validated against full ab initio calculations. At zero field, we confirm the existence of highly hybridized states that manifest as a qubit state exhibiting an approximately equal distribution between $|0\ensuremath{\rangle}$ and $|1\ensuremath{\rangle}$. The electric field application serves as a modulator for adjusting the contribution of these states. This phenomenon is general and is explored in the context of four distinct heterostructures. In addition, our study identified 222 possible combinations matching different layers on the conduction or the valence as promising host heterostructures for implementing vdW qubits.