A silicon singlet-triplet qubit driven by spin-valley coupling.

Area of Science:

• Quantum Computing
• Solid-State Physics
• Materials Science

Background:

• Electron spin qubits in silicon quantum dots are a promising platform for quantum computation.
• Controlling spin qubits typically requires complex on-chip micromagnets or striplines.
• Spin-orbit effects offer an alternative, potentially simpler control mechanism.

Purpose of the Study:

• To demonstrate a singlet-triplet qubit operating mode utilizing spin-orbit effects for fast, electrical control.
• To investigate the feasibility of high-frequency qubit evolution ( > 200 MHz).
• To probe charge noise in silicon double quantum dots using dynamical decoupling.

Main Methods:

• Implementation of a singlet-triplet qubit operating mode in a silicon metal-oxide-semiconductor double quantum dot.
• Utilizing spin-orbit interactions for electrical qubit control.
• Performing dynamical decoupling experiments to characterize charge noise.

Main Results:

• Achieved qubit evolution frequencies exceeding 200 MHz with fast electrical on/off switching.
• Demonstrated high logic gate orthogonality and long qubit dephasing times.
• Characterized the charge noise power spectral density up to 3 MHz, revealing a 1/f^α dependence (α ≈ 0.7).

Conclusions:

• Spin-orbit effects provide an effective method for fast, electrical control of silicon spin qubits, simplifying device architecture.
• The demonstrated qubit mode is suitable for high-fidelity quantum operations and noise spectroscopy.
• The study provides valuable insights into the charge noise environment affecting silicon quantum dots.