Syndrome-mitigation QEC (VEC)
Independent re-implementation of arXiv:2610.12400 (Google Quantum AI, found via @zlatko_minev): reweight shots by MWPM-vs-exact-ML decoder disagreement sectors to cancel residual logical errors in post-processing. Pre-registered d=3/5 experiment at p=0.05, seeds 0/1/2.
- VEC cuts residual logical bias 32–152× below plain MWPM and 15–101× below postselection on every seed; ⟨Z_L⟩ returns to 1.000±0.001 (ideal +1)
- PARTIAL: overhead ratio η<4 holds at d=5 (2.4) and d=7 (1.73, near the paper's quoted weights) but not d=3 (5.4–5.7) — matching the paper's distance trend
- Exact d=5/7 ML via transfer-matrix contraction verified against brute force; breakpoints: empty Y sector at p=0.01, threshold collapse, drift, 0.31%-error syndrome-only noise learning
cd apps/syndrome-mitigation-qec
uv venv .venv && source .venv/bin/activate
uv pip install -r requirements.txt
./run_all.sh