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engines/quan_loncar_v1/package/quan_loncar_optimizer/engine/quan_loncar_series_phase43/README.md · assembled 2026-07-29 15:57 UTC.

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Phase 43: feed-coupling geometry pullback

This phase differentiates the validated rank-one guided scattering residue. It includes the moving cavity pole, left/right QNM vectors, residue normalization, frequency-dependent guided beta poles, and analytic geometry partials of all incident/outgoing hole projections.

The nonzero scattering-residue singular value is the external guided full linewidth. Its simple-singular-value derivative gives gradients of external Q, the remaining nonguided-loss Q, and the guided external decay fraction. CouplingGeometryJacobian.objective_pullback(...) maps cotangents for those metrics back to the same 45-coordinate geometry vector used by Phase 41.

test_phase43.py validates the incident and outgoing port-map geometry partials against centered differences before the moving-pole chain rule is applied.

run_phase43_coupling_jacobian.py builds the production coupling Jacobian, checks its pole contraction against Phase 40, validates the simple-singular- value derivative directly, and exercises a mixed coupling-objective pullback.

run_phase43_conditioned_gate.py applies separate tolerances to the external metrics and to Q_other, whose small residual linewidth is formed by subtracting two close numbers. It does not relax any derivative, reciprocity, rank, bordered-solve, or pullback criterion.