Below-threshold surface-code memory: measured evidence
Research context
study · established · As of 2026-10-10
peer reviewed · 2024-12-09
- Study design
- Experimental superconducting surface-code logical memories at increasing code distances with repeated syndrome extraction and decoding.
- Reported result
- Distance-seven memory reports 0.143%±0.003% logical error per cycle and distance-two suppression factor 2.14±0.02.
- Limitations
- Device/decoder/noise-specific memory experiment; it does not establish universal logical gate performance or useful algorithm-scale fault tolerance. Retain the linked April 2026 figure-label correction when consulting the original study.
Google Quantum AI's Nature study, online 9 December 2024 and in the 2025 volume, reports a distance-seven surface-code memory using 101 physical qubits with logical error 0.143%±0.003% per cycle.
Key knowledge
Google Quantum AI's Nature study, online 9 December 2024 and in the 2025 volume, reports a distance-seven surface-code memory using 101 physical qubits with logical error 0.143%±0.003% per cycle. Increasing distance by two suppressed errors by a factor 2.14±0.02 in the tested devices, and the logical lifetime exceeded the best physical qubit by 2.4±0.3. This is significant below-threshold memory evidence within that architecture, not a universal fault-tolerant algorithm demonstration.
Conditions and scope
- The physical-qubit accounting, cycle definition, decoder and reported statistical uncertainty belong to this experiment. The inspected 28 April 2026 author correction repairs Figure 3a's repetition-code distance label and legend attribution; it does not revise these surface-code memory numbers.
- Extrapolation to longer distances, different noise, universal gates or practical algorithm advantage needs separate evidence.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Google Quantum AI and collaborators2 sources
Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: Abstract, experimental logical memory/scaling data and limitations; Nature 638 (2025); Correction body and publication metadata: Figure 3a repetition-code axis and legend attribution corrected; numerical surface-code memory claim unchanged. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
Entry details
Permanent link to this entry ↗- Record identity
- research-info-google-below-threshold-study
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference