Dynamics of van der Waals Charge Qubit in 2D Bilayers: Ab initio Quantum Transport and Qubit Measurement

TL;DR

This paper proposes a van der Waals charge qubit in 2D materials, analyzing its properties with ab initio calculations, and introduces a measurement setup with potential for integration into quantum computing.

Contribution

It systematically evaluates vdW charge qubits using density functional theory and quantum transport, and designs a low-decoherence measurement setup based on trilayer heterostructures.

Findings

A $$ greater than 20 meV causes rapid qubit state mixing.

Optimal qubit operation is achieved with specific charge stability and energy-level conditions.

The proposed setup enables integration into all-electronic quantum computing platforms.

Abstract

A van der Waals (vdW) charge qubit, electrostatically confined within two-dimensional (2D) vdW materials, is proposed as building block of future quantum computers. Its characteristics are systematically evaluated with respect to its two-level anti-crossing energy difference ($\Delta$). Bilayer graphene ($\Delta$ $\approx$ 0) and a vdW heterostructure ($\Delta$ $\gg$ 0) are used as representative examples. Their tunable electronic properties with an external electric field define the state of the charge qubit. By combining density functional theory and quantum transport calculations, we highlight the optimal qubit operation conditions based on charge stability and energy-level diagrams. Moreover, a single-electron transistor (SET) design based on trilayer vdW heterostructures capacitively coupled to the charge qubit is introduced as measurement setup with low decoherence and improved measurement properties. It is found that a $\Delta$ greater than 20 meV results in a rapid mixing of the qubit states, which leads to a lower measurement quantity, i.e. contrast and conductance. With properly optimized designs, qubit architectures relying on 2D vdW structures could be integrated into an all-electronic quantum computing platform.