Eliminating Leakage Errors in Hyperfine Qubits.

Area of Science:

• Quantum Information Science
• Atomic Physics
• Quantum Computing

Background:

• Population leakage outside the qubit subspace is a critical error source in quantum computing.
• Standard quantum error correction methods cannot address these harmful leakage errors.

Purpose of the Study:

• To demonstrate an optical pumping scheme for suppressing leakage errors in atomic hyperfine qubits.
• To address a major obstacle for quantum error correction and mitigation protocols.

Main Methods:

• Utilized a trapped ^{171}Yb^{+} ion system.
• Employed an optical pumping scheme leveraging selection rules and a narrow linewidth quadrupole transition.
• Applied interleaved randomized benchmarking to assess side effects on the qubit subspace.

Main Results:

• Achieved exponential suppression of leakage errors with each pumping cycle reducing leakage population by approximately a factor of 3.
• Demonstrated negligible side effects on the qubit subspace, with induced qubit memory error ≤2.0(8)×10^{-5} per cycle.
• Quantified qubit population decay to ≤1.4(3)×10^{-7} per cycle.

Conclusions:

• The developed optical pumping scheme effectively suppresses harmful population leakage errors in trapped ion qubits.
• The technique shows minimal impact on qubit fidelity, making it suitable for quantum error correction and mitigation.
• This work removes a significant barrier for robust quantum computing implementations.