B Grade B
Quantinuum Helios: Logical error rate
4 × 10⁻⁵ error per cycle
As stated in the source: “average QEC-cycle infidelity per logical qubit upper-bounded by 4 x 10^-5”
Uncertainty: 0 to 0.00004 (Upper bound only: no logical errors recorded in 5,000 shots per basis).
Caveats
Preprint. An upper bound from zero observed failures, not a measured rate. Memory (idle) error only, not a logical gate error. Comparing across platforms needs care because codes and per-cycle definitions differ. Upper bound: no errors were seen in 5,000 shots per basis.
- Set-up
- 48 logical qubits, distance-4 concatenated iceberg code, memory experiment; compared against unencoded physical memory error of 1.1 x 10^-4
- Method
- QEC memory experiment, concatenated iceberg code I8 o I6 (distance 4)
- Compared only with
- results in the group “concatenated iceberg d4 memory”
- Measured
- Not stated
- Published
- 25 February 2026
- Measured by
- Quantinuum
- Independent of the maker
- No
- Peer-reviewed
- No
- Repeated by others
- Not yet
Source
Computing with many encoded logical qubits beyond break-even, arXiv. Preprint. DOI: 10.48550/arXiv.2602.22211
History
- 27 October 2026: added
Spotted a mistake? Report an error, quoting r-000019.