TL;DR: The XZZX surface code is a modification of the standard surface code that performs much better when qubit noise is biased (e.g., when phase-flip errors dominate over bit-flip errors). Since many physi
The XZZX surface code is a modification of the standard surface code that performs much better when qubit noise is biased (e.g., when phase-flip errors dominate over bit-flip errors). Since many physical qubit platforms have naturally biased noise, XZZX codes can achieve much higher effective thresholds and lower overhead, making them a promising near-term approach.
Type
Modified surface code (biased-noise)
Overhead
Similar to surface code but optimized for biased noise
Threshold
~0.5% for depolarizing noise; much higher for biased noise
Key Result
Significantly outperforms standard surface code when noise is biased