Round 2 verification audit for C025

Model: gpt-5

Claim: A bit-flip error with probability p per cycle reduces the singlet fidelity by ~= 5.2 p when uncorrelated and ~= 3.2 p when correlated.

Source alignment: source/main.tex:145-145 (Theoretical error analysis)

Prior official verdict: verified with failure_reason None.

Executable evidence: run.py. Sandbox rerun logs: run.log.

Independent audit: I scanned the copied script for imports/shared helper dependencies and reran it through the sandbox. The code is self-contained in this attempt directory and targets the claim strategy: Simulate the steady-state singlet error for the uncorrelated (I_eX_e+X_eI_e split across ions) and correlated U_x(sqrt(2p)) bit-flip models and fit the linear slopes for p<0.01.. I checked the relevant family model rather than relying only on exit status; the rerun is treated as one reproducibility input.

Decision: Round 2 verdict is verified with failure_reason None and limitations []. Notes: Steady-state singlet error vs p at optimal Phi=pi/4, gamma=0.221pi, theta=0.716pi, error after drive (A), via 8000-cycle power iteration. Uncorrelated = local M_{x,0}=exp(-i(pi/2)X_e (x) I); correlated = U_x(sqrt(2p)); both parametrized so one-cycle one-ion-flip prob = p. Fitted slopes (p<0.01): uncorrelated 5.25/5.11 -> rounds 5.2; correlated 3.18/3.13 -> rounds 3.2. Paper: 5.2p and 3.2p. Match within tolerance; ratio ~1.65 confirms correlated gives lower steady-state error. Verified.