Fast universal quantum gate above the fault-tolerance threshold in silicon

Area of Science:

• Quantum computing
• Quantum error correction
• Solid-state qubits

Background:

• Fault-tolerant quantum computers require quantum error correction.
• Surface codes are a promising error correction strategy.
• Silicon spin qubits offer nanofabrication advantages but face fidelity challenges.

Purpose of the Study:

• To demonstrate high-fidelity two-qubit gates in silicon spin qubits.
• To achieve universal gate fidelities exceeding the fault-tolerance threshold.
• To enable scalable silicon quantum computers.

Main Methods:

• Utilized fast electrical control with a micromagnet-induced gradient field.
• Employed a tunable two-qubit coupling mechanism.
• Identified optimal qubit rotation speed and coupling strength for high fidelity.

Main Results:

• Achieved a two-qubit gate fidelity of 99.5%.
• Demonstrated single-qubit gate fidelities of 99.8%.
• Successfully executed Deutsch-Jozsa and Grover search algorithms.

Conclusions:

• Universal gate fidelity beyond the fault-tolerance threshold has been demonstrated in silicon spin qubits.
• Fast electrical control and tunable coupling overcome previous fidelity limitations.
• This advancement paves the way for scalable silicon quantum computing.