Highly Tunable Two-Qubit Interactions in Si/SiGe Quantum Dots by Interchanging the Roles of Qubit-Defining Gates

TL;DR

This paper introduces a method to reconfigure gate roles in Si/SiGe quantum dot spin qubits, greatly enhancing exchange coupling tunability and reducing control complexity for scalable quantum computing.

Contribution

The study demonstrates in situ role swapping of nanogates to improve exchange interaction control without additional hardware complexity.

Findings

Achieved several orders of magnitude improvement in exchange coupling tunability.

Reduced unintended single-qubit phase shifts.

Enabled scalable multi-qubit control with minimal overhead.

Abstract

Silicon quantum dot spin qubits have become a promising platform for scalable quantum computing because of their small size and compatibility with industrial semiconductor manufacturing processes. Although Si/SiGe heterostructures are commonly used to host spin qubits due to their high mobility and low percolation density, the SiGe spacer creates a gap between the qubits and control electrodes, which limits the ability to tune exchange coupling. As a result, residual coupling leads to unwanted single-qubit phase shifts, making multi-qubit control more difficult. In this work, we explore swapping the roles of overlapping nanogates to overcome this issue. By reconfiguring the gate voltages, we demonstrate in situ role switching while maintaining multi-qubit control. Additionally, this method significantly improves the tunability of exchange coupling by several orders of magnitude over the traditional approach. This strategy reduces unintended single-qubit phase shifts and minimizes the complexity of multi-qubit control, supporting scalable growth with minimal experimental overhead.