Round 2 verification audit for C055

Model: gpt-5

Claim: The steady-state error caused by residual spin-motion entanglement is found in simulation to be almost identical to that introduced by U_x(sqrt(2 p)), so the main-text simulations apply to both error sources.

Source alignment: source/supp_content.tex:84-84 (Supp. Mat. S2)

Prior official verdict: partial 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 both error models versus p and confirm the steady-state singlet errors coincide.. 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 partial with failure_reason None and limitations ['paper_text_only_reimplementation']. Notes: Claim (supp S2): steady-state error from residual spin-motion entanglement is almost identical to that from U_x(sqrt(2p)). Reimplemented both: (A) unitary U_x(eps); (B) state-dependent residual displacement V=exp[(alpha a^dag - alpha a)(x)S_x] on spin(x)truncated oscillator (NFOCK=16, CPTP verified), motion traced out. Calibrated eps and alpha to the SAME operational p (single-event one-flip probability from |dn,dn>, supp l.82-84). Matched-p steady-state errors 1-F: p=0.005 1.57e-2 vs 1.57e-2 (0.5%); 0.01 3.09e-2 vs 3.12e-2 (1.0%); 0.02 6.01e-2 vs 6.13e-2 (2.0%); 0.04 (4.0%); 0.06 (6.1%). Max rel diff 6.1%, <1% at small p. Almost identical, as claimed. Also confirmed paper's eps=sqrt(2p) (operational p_A~0.0099 at eps=sqrt(20.01)). Requires reimplemented motional model + Fock truncation => partial.