Microwave-Frequency Scanning Gate Microscopy of a Si/SiGe Double Quantum Dot

Area of Science:

• Quantum Computing
• Condensed Matter Physics
• Materials Science

Background:

• Conventional transport measurements lack spatial resolution for quantum dot states.
• Scanning tunneling microscopy offers high spatial resolution but is slow.
• Combining spatial and energy resolution with speed is crucial for quantum device characterization.

Purpose of the Study:

• To develop a technique merging spatial resolution of scanning probe microscopy with speed of microwave measurements.
• To characterize spin, orbital, and valley states in silicon-germanium double quantum dots (DQDs).
• To demonstrate the feasibility of scanning gate experiments on Si/SiGe devices.

Main Methods:

• Coupling a metallic tip to a Si/SiGe DQD integrated with a charge detector.
• Using a dc-biased tip to control DQD occupancy.
• Applying microwaves through the tip to induce photon-assisted tunneling (PAT).
• Analyzing tunneling resonances to infer the DQD level diagram.

Main Results:

• Demonstrated tip-induced control over DQD occupancy.
• Successfully drove PAT using microwave signals delivered via the tip.
• Resolved excited states with an energy resolution of approximately 65 μeV.
• Observed energy splittings consistent with valley states in Si/SiGe.

Conclusions:

• The developed technique successfully combines spatial resolution and energy sensitivity with microwave measurement speed.
• This method enables high-resolution characterization of quantum states in Si/SiGe DQDs.
• The findings validate the potential of scanning gate experiments for advanced quantum device analysis.