Reducing charge noise in quantum dots by using thin silicon quantum wells.

Area of Science:

• Quantum Computing
• Semiconductor Physics

Background:

• Charge noise in host semiconductors hinders spin-qubit performance and large quantum processor control.
• Engineering gate-defined quantum dots for reduced charge noise is complex.

Purpose of the Study:

• To investigate the link between global semiconductor disorder and local charge noise in quantum dots.
• To systematically improve charge noise in 28Si/SiGe heterostructures.

Main Methods:

• Measured local charge noise in quantum dots.
• Measured global disorder in host semiconductors using macroscopic Hall bars.
• Analyzed 5 nm thick 28Si quantum wells and 100 mm wafers.

Main Results:

• Found that improved scattering properties and uniformity of the 2D electron gas correlate with reduced charge noise.
• Achieved a minimum charge noise of 0.29 ± 0.02 μeV/Hz½ at 1 Hz.
• Extrapolated noise reduction to nearly one order of magnitude improvement in CZ-gate fidelities.

Conclusions:

• Demonstrated a connection between macroscopic semiconductor properties and microscopic charge noise.
• Highlighted the importance of a clean, uniform crystalline environment for high-fidelity spin qubits.
• Paved the way for integrating long-lived, high-fidelity spin qubits into larger quantum systems.