Quantifying error and leakage in an encoded Si/SiGe triple-dot qubit.

Area of Science:

• Quantum computing
• Quantum information science
• Solid-state spin qubits

Background:

• Qubit development faces challenges balancing coherence and control.
• Encoded qubits offer noise resilience and simplified control mechanisms.
• Leakage errors are a key challenge for encoded qubits.

Purpose of the Study:

• Demonstrate high-fidelity operation of an exchange-only qubit.
• Utilize a subsystem of three coupled electron spins in silicon quantum dots.
• Investigate control mechanisms compatible with scalable quantum systems.

Main Methods:

• Encoding a qubit in a three-electron spin subsystem.
• Utilizing gate-voltage-controlled exchange interaction for qubit control.
• Employing a modified blind randomized benchmarking protocol to quantify errors.

Main Results:

• Achieved high-fidelity operation of the exchange-only qubit.
• Demonstrated control exclusively via fast voltage pulses, avoiding high-frequency fields.
• Measured an average total error of 0.35%, with 0.17% attributed to leakage.

Conclusions:

• The exchange-only qubit shows excellent performance and full gate-voltage control.
• This qubit is compatible with low magnetic field environments, aiding integration.
• The demonstrated approach is highly attractive for constructing large-scale quantum processors.