Experimental Quantum Error Correction below the Surface Code Threshold via All-Microwave Leakage Suppression.

Area of Science:

• Quantum Information Science
• Quantum Computing
• Quantum Error Correction

Background:

• Scalable quantum computing relies on quantum error correction (QEC) to suppress errors.
• Leakage errors, where quantum information escapes the computational subspace, pose a significant challenge to QEC scalability.
• These leakage errors create long-lived, correlated errors that hinder performance.

Purpose of the Study:

• To demonstrate a quantum memory operating below the error threshold by implementing an all-microwave leakage suppression architecture.
• To reverse the above-threshold scaling caused by unmitigated leakage errors in quantum systems.
• To enable more advanced quantum error correction implementations.

Main Methods:

• Implementation of an all-microwave leakage suppression architecture.
• Utilizing a distance-7 surface code for encoding logical qubits.
• Integration of a hardware-efficient leakage reduction unit for data qubits and fast reset for ancilla qubits.

Main Results:

• Achieved a logical error suppression factor of Λ=1.40(6), demonstrating operation below the error threshold.
• Successfully reversed the detrimental above-threshold scaling (Λ<1) previously caused by leakage errors.
• Suppressed the average leakage population by a factor of 72 to 6.4(5)×10^{-4} after 40 cycles.

Conclusions:

• The demonstrated all-microwave control architecture is viable for suppressing critical errors at scale.
• This approach paves the way for the development of more advanced quantum error correction techniques.
• Effective leakage suppression is crucial for realizing fault-tolerant quantum computing.