Polytrion — a digital twin
that cannot drift silently

What you do with it

You describe the operation. The rules become declared artefacts, checked before a run and on every step of it, and every answer comes back with the evidence attached. Drift becomes something you are shown on a schedule instead of something you discover.

Four properties, and the combination is what is unusual

There is very little to say about the internals here on purpose — they are ours to maintain, not yours to learn. What matters to somebody deciding whether to use the platform is what holds, not how it is built.

Nine published answers, in nine fields, none of them another simulator's output

Every entry was selected on one rule: the right answer must already be known to more digits than the engine can deliver, and it must not be a simulation. A closed form, an exactly solvable finite system, or a linear solve over a finite chain — in that order. A heavily replicated numerical constant is second best; another code's output is not accepted at all. That rule excludes most of the simulation literature, and it is what makes agreement informative — if the reference is somebody's program, reproducing it means reproducing their conventions, and disagreement localises nothing.

Every row's acceptance rule is a rule, not a number — “three standard errors of the ensemble mean at this replication count, plus the declared tick-quantisation allowance,” written into the experiment document before any run exists. “Within one per cent” is a number that can be chosen after seeing the answer. Every completed study reports zero invariant findings.

Four more fields, where the reference is a mechanism or a reference tool

These are where the construction's other claim — that a mechanism can be checked before it is sampled — was exercised.

Where the engine was pointed at an open question, not a known answer

The quantum-error-correction row above is a reference-tool agreement. This is what came out of the same world once it was asked something nobody had the answer to.

Preprints.org Article

Backlog Metastability in Windowed Quantum Error Correction Decoding

• The standard stability condition is inadequate. For windowed decoders whose per-window cost grows superlinearly in detection events, stability is not a threshold at ρ < 1 but a basin — a stable operating point and an unstable boundary that noise erodes downward.
• Forty per cent of nominal headroom is not headroom. A decoder at cost exponent γ = 1.5 and mean utilisation ρ₀ = 0.6 fails without provocation: mean time to failure 1,344 ± 289 rounds, about 1.3 ms of wall clock at a 1 µs cycle.
• A production decoder's cost exponent is anisotropic. PyMatching 2 measures near-linear (γ ≈ 1.1–1.2) when a window grows in length, approximately quadratic (γ ≈ 2) when the same window grows denser. Bursts travel along the dangerous axis.
• Clustered content is worse than dense content. At matched event count, spatially clustered windows — the syndrome footprint of leakage and cosmic-ray bursts — cost 7.6× length-grown and 4.8× uniformly densified ones.
• More buffer makes the greedy policy strictly worse. Greedy catch-up is precisely the divergent policy; a bounded window restores stability, and the measured stability edge lands on a closed-form line.

surface codereal-time decodingminimum-weight perfect matchingfault-tolerant quantum computingstate-dependent queuesstochastic stabilitycorrelated error burstsdiscrete-event simulation

Jean-Jacques Dubray · Cognitive Fab LLC Posted 21 August 2026 doi: 10.20944/preprints202608.1425.v2

Read it on Preprints.org ↗