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Sustaining high-fidelity quantum logic in neutral-atom circuits via mid-circuit operations
Rui Lin, You Li, Le-Tian Zheng, Tai-Ran Hu, Si-Yuan Chen, Hong-Ming Wu, Yu-Chen Zhang, Hao-Wen Cheng, Yu-Hao Deng, Zhan Wu, Ming-Cheng Chen, Jun Rui, Chao-Yang Lu, Jian-Wei Pan
TL;DR
Maintaining neutral-atom gate fidelity across repeated circuit rounds is challenging because fidelity can drop after the first rounds. This paper uses mid-circuit Raman sideband cooling and reports 99.81(1)% loss-corrected CZ fidelity, with ~99.8% fidelity sustained across rounds without observable degradation.
Problem
Gate fidelity can drop from the second operational round onward without active cooling, limiting evidence for sustained performance in repeated neutral-atom operations.
Method
The framework applies mid-circuit Raman sideband cooling to refresh the atoms during repeated gate operations.
Results
99.81(1)% loss-corrected CZ gate fidelity was measured, while ~99.8% fidelity was sustained across multiple rounds without observable degradation.
Takeaways & Limitations
Mid-circuit cooling supports sustained high-fidelity neutral-atom gate operation across multiple operational rounds.
Abstract
from arXiv · showhide
The realization of fault-tolerant quantum computation hinges on the ability to execute deep quantum circuits while maintaining gate fidelities consistently above error-correction thresholds. Although neutral-atom arrays have recently demonstrated high-fidelity two-qubit gates and early-stage logical quantum processors, sustaining such high performance across deep, repetitive circuits remains a formidable challenge due to cumulative motional heating and atom loss. Here we demonstrate a sustainable neutral-atom framework that overcomes these limitations by integrating a suite of hardware-efficient mid-circuit operations. We report a two-qubit controlled logic gate with a raw fidelity of 99.60(1)%, which is further increased to a fidelity of 99.81(1)% via non-destructive erasure detection. Crucially, by implementing in-circuit Raman sideband cooling and qubit re-initialization, we demonstrate that gate fidelities can be maintained at the ~99.8% level across multiple operational rounds without observable degradation. By actively managing the internal and motional entropy of the system mid-stream, our in-situ refreshable architecture provides a critical pathway for executing the repeated syndrome-extraction cycles required for large-scale, continuous quantum error correction.
Figures
The figures show a refreshable neutral-atom architecture that combines high-fidelity CZ gates, loss-resolved measurement, and mid-circuit cooling to sustain performance across repeated rounds. Raman sideband cooling maintains approximately 99.8% loss-corrected CZ fidelity over five rounds without observable degradation, unlike control conditions.
- Sustaining high-fidelity quantum logic in deep circuits: The refreshable architecture depicts cumulative motional heating and entropy buildup from repetitive gates and photon scattering as a thermal-decay mechanism across circuit depth.The schematic relates circuit scaling in qubit number and depth to degradation of gate performance.
- Sustaining CZ gates across multiple mid-circuit rounds: ~99.8% loss-corrected CZ fidelity is sustained across five mid-circuit rounds with Raman sideband cooling, without observable degradation, while local gray molasses and no cooling decline after round two.The comparison includes three conditions and shows significant drops from the second round onward without active Raman sideband cooling.