Capability gated checks reveal limits of quantum decoder correctness
Capability-Gated Conformance Testing of Quantum Error-Correction Decoder Libraries
Hardware Architecture
Summary
Quantum computers use special codes to fix errors, and programs called decoders work out how to fix these errors. This paper looks beyond usual tests to see if these decoders really do what they claim without needing a perfect answer to check against. The authors find that many decoders don’t clearly state how well they guarantee correctness, and sometimes change their fixes when given the same problem in a slightly different way. They provide tools to verify decoders more thoroughly and independently.
What this means in practice
- •For quantum software developers: Check if quantum error decoders meet claimed guarantees without needing perfect error knowledge, ensuring decoder reliability in quantum simulations and experiments.
- •For quantum hardware integrators: Verify that decoders handle error syndromes consistently under different data presentations, helping hardware teams choose robust decoders for real devices.
Authors
Jiachen Shen, Hui Zhong
Abstract
A quantum error correction decoder is a library other people's results depend on, judged in one dominant way. Sample errors, decode, and count wrong logical observables. We ask what else can be checked there. Our conformance contract needs no oracle. One check asks that a returned correction explain the syndrome in the caller's index space. The other hands a decoder one instance under two presentations differing only in bookkeeping, where two feasible corrections of different weight prove the heavier is not minimum-weight. Verdicts are gated on what each library declares, so a firing contradicts a published guarantee. Nine configurations from five public libraries give three results. Documentation answers 4 of 54 capability questions. Bounded-distance correctness, the property callers most depend on, has a direct declaration yield of 0.0%, though its hypotheses hold in 62.1% of cases. Presentation sensitivity is real but shallow. One solver moved to a 26% heavier correction under a different numbering, which reaches the logical class at most once in twenty thousand shots. Established evaluation misses corruptions that preserve logical parity, while one summation over the caller's weights catches every one we injected. All 639 certificates ship as bundles a standalone verifier re-derives from first principles.