Validation contract

Let $\mathcal{A}$ be a finite nonempty predeclared collection of region–decoder tasks, and let $K=|\mathcal{A}|$. If multiple decoders or noise configurations for the same region are tested and selected using the validation results, they count as separate tasks in $K$.

For every $A\in \mathcal{A}$, the validation procedure:

1. prepares an independent Bell pair $QC$;

2. implements exactly the declared channel ${\Lambda }_{0,A}$ in (eq:implemented);

3. measures $XX,YY,ZZ$ on $Q,C_{\mathrm{out}}$ in separate predeclared settings;

4. assigns a complete bounded score to every attempted trial.

Decoder training precedes held-out validation. The same logical channel must be tested in all three settings.