QEC experiments and round traces

Purpose and scope

Defines an explicit error schedule and round trace over correction maps. Stochastic noisy simulation and an algebraically verified result in a single-error model are different experiments.

Core design rules

• An experiment selects an exact-version built-in QEC artifact and declares 1..8 compile-time rounds.
• Each round injects at most one supported single-qubit Pauli error.
• The result records syndrome, selected correction, residual class, logical invariant and decoder provenance.

Example from the original

This example illustrates the design recorded in the original. It is not by itself a claim of executable or stable support; check required options and the current version.

qec experiment steane_rounds {
  code: qec.steane7_code@0.4;
  rounds: 3;
  inject round 1 X(q[2]);
}

Limits and interpretation

• Threshold estimation, logical error rates, multiple physical errors and actual syndrome-extraction circuits are outside this scope.
• A 25-qubit repetition-code artifact is not general 25-qubit statevector simulation; it belongs to a specific algebraic model.

Status and implementation boundary

The proposal aims to turn existing exact correction artifacts into structured experiments. Do not interpret a successful round trace as fault-tolerant hardware evidence.