OPD-aware squeezing and Gaussian correlations from dual-comb interferograms

We introduce an optical-path difference (OPD)-aware, model-agnostic pipeline to detect quadrature squeezing and Gaussian correlations (including entanglement where applicable) directly from dual-comb interferograms. Because the effective measurement basis rotates with optical-path difference (quadrature-like near the centerburst, intensity-like in the wings) we perform sub-sample (fractional) delay alignment, whiten traces in a co-moving OPD frame, extract time–frequency modes, and build per-mode covariance matrices. Duan–Simon witnesses, symplectic eigenvalues, and a multiplexed quantum-noise-reduction (QNR) metric yield OPD-resolved "noise-grams" across thousands of RF teeth. Shot-noise normalization uses variance-vs-power regression and out-of-band electronics estimates (confirmed with dark runs). We validate on public squeezed-comb data and set calibrated nulls via shuffle controls on high-SNR EOS-DCS (≈90% shot-noise-limited lines). By March we will release a reproducible notebook and report robustness to loss, mode mismatch, detector imbalance, and phase drift.