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

Area of Science:

• Quantum computing
• Semiconductor device physics

Background:

• Silicon quantum dot spin qubits are promising for scalable quantum computing.
• Si/SiGe heterostructures offer high mobility but have limitations in qubit control due to the SiGe spacer.
• Existing methods struggle with precise multi-qubit control due to residual coupling and limited exchange coupling tunability.

Purpose of the Study:

• To overcome limitations in multi-qubit control for silicon quantum dot spin qubits.
• To improve the tunability of exchange coupling in Si/SiGe heterostructures.
• To reduce unintended single-qubit phase shifts in quantum processors.

Main Methods:

• Exploration of swapping overlapping nanogate roles.
• In situ reconfiguration of gate voltages for role switching.
• Demonstration of maintaining multi-qubit control post-reconfiguration.

Main Results:

• Achieved up to 3.6 times improvement in exchange coupling tunability.
• Successfully demonstrated in situ nanogate role switching.
• Reduced unintended single-qubit phase shifts, simplifying multi-qubit control.
• Maintained robust multi-qubit control throughout the process.

Conclusions:

• The proposed nanogate swapping strategy effectively addresses challenges in silicon quantum dot qubit control.
• This method enhances scalability for quantum computing by minimizing experimental overhead and complexity.
• The improved tunability and reduced phase shifts pave the way for more reliable quantum processors.