Anisotropic exchange interaction of two hole-spin qubits

Area of Science:

• Quantum computing
• Semiconductor physics
• Spintronics

Background:

• Semiconductor spin qubits, particularly silicon hole spin qubits, offer potential for large-scale quantum computers due to fast all-electrical control.
• Overcoming charge and nuclear spin noise is crucial, with sweet spots offering a partial solution.
• A significant hurdle has been demonstrating reliable two-qubit interactions, particularly understanding exchange coupling under strong spin-orbit interaction.

Purpose of the Study:

• To investigate the exchange coupling between two hole-spin qubits in a silicon fin field-effect transistor.
• To demonstrate electrical tunability of qubit interactions and achieve fast, high-fidelity two-qubit gates.
• To explore the role of spin-orbit interaction in anisotropic exchange and its implications for quantum gate design.

Main Methods:

• Fabrication and characterization of two coupled hole-spin qubits within a silicon fin field-effect transistor.
• Electrical manipulation of the exchange interaction between qubits, tuning it from 500 MHz to near zero.
• Implementation and timing of a conditional spin-flip operation, achieving a 24 ns gate time.

Main Results:

• Demonstrated electrical tunability of exchange splitting in silicon hole spin qubits.
• Achieved a conditional spin-flip operation in 24 nanoseconds.
• Observed anisotropic exchange coupling due to spin-orbit interaction, leading to spin rotation during tunneling.
• Showcased engineered exchange Hamiltonians enabling high-fidelity, fast two-qubit controlled rotation gates independent of magnetic field orientation.

Conclusions:

• The engineered anisotropic exchange interaction in silicon hole spin qubits circumvents the typical speed-fidelity trade-off for controlled rotation gates.
• This approach is robust across various magnetic field orientations and qubit variations.
• The findings present a promising pathway for realizing large-scale quantum computers using industrial semiconductor technology.