B Grade B
Google Willow: Logical error rate
1.43 × 10⁻³ error per cycle
As stated in the source: “0.143% ± 0.003% error per cycle (distance 7)”
Uncertainty: 0.0014 to 0.00146 (0.143% ± 0.003% as stated).
Caveats
This is one logical qubit stored as a quantum memory, not a logical qubit doing computation. The figure uses an offline decoder; real-time decoding was only shown at distance 5 with a higher error. The authors say rare correlated error events, about one per hour, limit performance.
- Set-up
- Distance-7 surface code memory using 101 qubits; QEC cycle time 1.1 µs; offline neural-network decoder. A distance-5 code with a real-time decoder reached 0.35% ± 0.01% per cycle.
- Method
- Surface code memory, logical error per cycle, neural-network decoder (offline)
- Compared only with
- results in the group “surface code d7 memory”
- Measured
- Not stated
- Published
- 9 December 2024
- Measured by
- Google Quantum AI
- Independent of the maker
- No
- Peer-reviewed
- Yes
- Repeated by others
- Not yet
Source
Quantum error correction below the surface code threshold, Nature (Springer Nature); preprint arXiv:2408.13687. Peer-reviewed paper. DOI: 10.1038/s41586-024-08449-y
Comparable results
| Machine | Value | Set-up | Published | Measured by | Grade | Record |
|---|---|---|---|---|---|---|
| Google Willow | 7.72 × 10⁻⁴ | surface code d7 memory | 11 Nov 2025 | Maker | B | r-000002 |
History
- 27 October 2026: added
Spotted a mistake? Report an error, quoting r-000001.