Radio-frequency single electron transistors in physically defined silicon quantum dots with a sensitive phase...

Area of Science:

• Quantum computing
• Semiconductor device physics
• Quantum information science

Background:

• Radio-frequency reflectometry is crucial for reading out spin qubits in semiconductor quantum dots.
• Achieving a large phase response, essential for sensitive measurements, remains a practical challenge.

Purpose of the Study:

• To investigate radio-frequency single electron transistors (RF-SETs) utilizing physically defined quantum dots in silicon-on-insulator (SOI).
• To explore quantum dots without top gate structures that may impede RF reflectometry.
• To precisely determine gate-dependent device admittance using a model accounting for parasitic components.

Main Methods:

• Fabrication of RF-SETs with physically defined quantum dots in SOI.
• Characterization of device admittance by analyzing the gate-dependent reflection coefficient (amplitude and phase).
• Modeling of device behavior, including parasitic components, to understand experimental observations.

Main Results:

• Observation of clear Coulomb peaks in both amplitude and phase of the reflection coefficient.
• Demonstration of a remarkably large phase signal of approximately 45°.
• Electrical circuit analysis attributing the large phase signal to effective impedance matching and detuning from resonance frequency.

Conclusions:

• The study successfully demonstrates a large phase signal in RF-SETs for spin qubit readout.
• The findings suggest that optimizing impedance matching and resonance detuning is key to enhancing readout sensitivity.
• Results provide valuable insights for designing and simulating reflectometry circuits to improve qubit readout performance.